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24 CIRCUITS as of  1-2-2019

                                         to Index
INTRODUCTION
This e-book presents some interesting projects for Model Railways.
Talking Electronics has produced two books for Model Railway enthusiasts (book-2 is now out of print).
The two books are:
Electronics for Model Railways 1:
Electronics for Model Railways 2:
The projects in these books can be found on Talking Electronics website in the left-hand column.
Since releasing these two books, we have designed some extra projects and more are being released all the time.
The projects will be presented in this eBook and you will need to come back on a regular basis to see the updates.


Colin Mitchell

If you have DCC Digital Command Control on your model railway, or are thinking about using it or starting a layout with this feature, here is a website dedicated to helping you:
http://www.dccconcepts.com.au/

Digital Command Control is a standard for a system to operate model railways so that two or more locomotives can be controlled independently on the same section of track.
We will not be covering any projects for DCC so it's best to visit the DCC website.


NOTE:
Many of the projects and circuit and ideas in this eBook are available from Talking Electronics as complete kits, fully assembled, or as components or on the web at very low prices.
Email: Colin Mitchell and ask for assistance before launching out on your own.

THEORY & PROJECTS

     to Index

THE MULTIMETER
I test all my projects with a $5.00 multimeter !!
WHY???
Because an analogue multimeter puts a load on a circuit and the reading MUST be genuine.
Secondly, an analogue multimeter will show fluctuations in a circuit and show when a certain part of a circuit is not maintaining stability.
And thirdly, an analogue multimeter will respond to changes and pulses much faster than a digital meter.
Lastly, if I can design and test a circuit with a cheap meter, everyone else should be able to do the same when using a more-expensive meter.
Finally, an analogue meter lasts a lifetime. And if you damage it, the cost is only $5.00
And you get 500mA range, a digital meter gives 200mA.
Analogue Meters are on eBay
I have digital meter when I want to read voltages accurately.
 


If you buy two multimeters, you can test currents up to 1 amp by placing the multimeters in PARALLEL as shown in the following diagram:

The red and black probes go to the positive and negative terminals of the project you are testing and you simply add the current readings (shown by the pointer on each meter) to get a final value (up to one amp). 

Current flows through the multimeter from the positive probe to the negative probe and the arrow on top of the meter above shows this direction.
This is how we arrive at that statement:
When taking a measurement of CURRENT, the voltage on the positive probe will be very slightly higher than the voltage on the negative probe, because a very small voltage will be dropped across the CURRENT RESISTOR inside the meter. The meter is actually measuring the voltage across this resistor and you are reading the pointer where the scale says 0-500mA
We know that current flows from positive to negative and when you trace the circuit above, you can see the meter is part of this circuit.
When measuring CURRENT, you use exactly the same reasoning as when you are measuring voltage.
Look at the circuit or project and work out which point will have the (slightly) higher voltage. The red probe goes to this point.
When measuring CURRENT, even the wires will have a slightly higher voltage at one end. This is the end for the red probe.
When measuring CURRENT, the circuit has to be CUT and the probes inserted into the CUT.  You cannot measure the current taken by a component by placing the probes "across it." You have to cut a wire or a track or desolder one of the wires.

If you cannot remember how to connect a multimeter when testing CURRENT, tilt it slightly so the positive terminal is higher than the negative terminal and lay the red probe on the bench HIGHER than the black probe and NOW connect the probes to the project. Now look for the part of the circuit with the higher voltage. Put the red probe on this point.

ooooooooo00000000000000000ooooooooooooo

Another other handy piece of test equipment to test DCC rails is the TRACK TESTER shown below:


The TRACK TESTER is HERE

 
The POWER SUPPLY  
Every project needs POWER. Power is ENERGY and it comes from a battery or a POWER SUPPLY.
We are going to describe a POWER SUPPLY that connects to the mains of your house.
A Power Supply provides TWO THINGS. It provide a VOLTAGE and a CURRENT.
The voltage can be oscillating "up-and-down" and we call this ALTERNATING VOLTAGE and it is given the letters AC. The letters AC actually mean ALTERNATING CURRENT and the term comes from the very beginning of supplying energy to houses and the two rival companies had a war. One company supplied DIRECT VOLTAGE and the other supplied ALTERNATING VOLTAGE. The first was called DC and the second called AC.
The voltage at all power points of a house is ALTERNATING and to convert it to DC requires a transformer, a rectifier and a smoothing capacitor called an electrolytic.
We will not be concerned with any of these components but the three values we will be covering is: THE VOLTAGE    THE CURRENT and if the output is AC or DC.
A POWER SUPPLY plugs into your wall socket and delivers a VOLTAGE, CURRENT and lets you know if the output is AC or DC. A Power Supply can also be called a Wall Wart, Plug Pack, Adapter or "Converter."

A POWER SUPPLY FOR YOUR MODEL RAILWAY
You will need at least 2 or 3 different power supplies for your layout. This is because a layout requires at least to different voltages.
Normally, these are very expensive, buy we are going to show how to use all sorts of "junk" and "discarded" power supplies from computers, shavers, toothbrushes, toys, printers, faxes, mobile phones, old electric drill chargers and anything you no-longer use, and convert them into a power supply.
They will cost you little or nothing and they will work PERFECTLY.
But you need to know what you are doing as there are lots of different options.
The Li-ion 4-cell power supply we will be describing is equal to $100 power supply (from a model railway supplier) and the $35 Power Supply (we will be describing)  using 5 Li-ion cells can be used as a BENCH POWER SUPPLY for all  your testing and is equal to a $100 product. And some of the other power supplies we will be describing ill cost you either nothing or just a few dollars.
Once you have a power supply, we will describe the next item on your list a THROTTLE. This is the module that connected between a power supply and delivers a voltage and current to the track to control the speed of the loco.


A typical "Wall Wart" or "Plug Pack" or "Adapter"

Power supplies are also called wall warts, plug packs, chargers or adaptors and must be of the type that is SAFE. In other words, you must be able to touch the output wires and the tap in the kitchen and not get killed.
This is not a joke. If the adaptor is only designed to be used with a fully plastic item, it may be lacking isolation as you cannot touch any of the wiring. This will only refer to very old devices where a simple capacitor was used to convert the household voltage to a situation where the output was fairly low current.
Throw out anything that you are not absolutely sure of its safety-factor.
Now we have a handful of say 10 different, old, unwanted, useless adaptors.
We are going to show how to connect two or three together to produce a voltage suitable for many of our railway projects.
 
Make 4 piles. The first will have current ratings from 100mA to 500mA.
The next will have current ratings from 600mA to 1 amp
The third pile will be 1 amp and higher.
And the fourth pile is for those adaptors that deliver AC.
From these piles you will be able to make a power supply using two adaptors and wiring the outputs IN SERIES.
Many of the CDU projects from Talking Electronics need an input of 20v DC to 25v DC.  The current can be as low as 100mA as the electrolytics in the CDU will take up to 1 amp if the the power supply can deliver this current, but if the available current is 100mA, the CDU will simply take longer to charge the electrolytic.
So, almost any power supply can be used and it is the voltage that is needed so the electrolytic charges to the maximum.
If you have two 12v DC adaptors with a current rating from 100mA to 1 amp, they can be combined together by connecting the output wires IN SERIES. If one adaptor is 100mA and the other 1amp, they can be combined and all that will happen is the output current will be limited to 100mA. You can even connect 3 adaptors in series to get a total voltage of 25v.
This is one way to use low-output-voltage adaptors to power the CDU project on your model railway.
Some adaptors are only 3v to 4v to 5v and they can all be combined. 

It is difficult to combine AC adaptors as the voltage from each adapter is rising and falling and if the rise-and-fall from one is not identical to the other, the output voltage will be unknown. You can try connecting two in series and see if the voltage and current is as expected.
AC adaptors are very uncommon. In general you can expect the output to be DC.

USING ADAPTORS IN PARALLEL
You can also connect adaptors in PARALLEL. This involves connecting the negative output of one the the negative of the other and the two positives together.
Ideally, the output voltage of each adaptor should be the same as this will equalise the load-sharing.
But many adaptors have a high output voltage that drops as the load is applied.
For instance a 12v 500mA adaptor can be as high as 17v on no-load and this voltage will drop to 12v when 500mA is flowing.
The other adaptor may be 14v on no-load and 12v when 500mA is flowing.
These two adaptors can produce a 12v 1 amp power supply ONLY IF the actual sharing between the two is EQUAL.
It is pointless placing a 12v and 5v adaptor in parallel as the 5v adapter will never deliver any current.
The two adapter share 50:50 when the output voltage is exactly the same. This will never be the case but no damage will be done as each adapter has a diode on the output that prevent one adapter passing any current to the other.

This is a good way to use up the box of old adapters.

Here is a typical 18v power supply for a model railway.  This is the ideal supply, but it is expensive and our aim is to show how to produce the same output voltage by using much cheaper items (Plug Packs etc.)


18v Power Supply

USING ADAPTORS IN SERIES
Here are two Plug Packs connected in series:

You can connect any TWO or THREE together and the output voltage will be the sum of all the voltages and the current will be determined by the lowest current of the 3 adapters.

This is very handy for CAPACITOR DISCHARGE UNITS as they need a voltage of approx 16v to 25v DC to fully charge the capacitors.

If you do not have any old Plug Packs, you can buy new ones on eBay for a few dollars.

You can buy 1Amp or 2Amp Plug Packs.
You will need:
1 x 12v adapter  and 1 x 5v  adapter for a THROTTLE.
2 x 12v 1Amp adapters for a Capacitor Discharge Unit.
Total of 4 Plug Packs.

Here are some examples:



THE BEST ADAPTOR:

 

The best DC adapter for all the CDU modules is a 24v or 30v supply made from two  12v adaptors in series of three 10v adaptors in series.
If the CDU module has an on-board regulator, the 30v supply is the best as it will charge the electros to a maximum of 27v.
For all the other CDU modules, you should use two 12v adaptors in series and the electros will charge to about 23v. 

THE
ALTERNATIVE TO A WALL WORT
Because a Wall Wort producing 13v AC or 27v DC is fairly difficult to obtain (almost impossible) Talking Electronics has produced a number of CDU modules that accept almost any voltage (AC or DC or DCC) from 9v to 15v (either AC or DC) and the on-board voltage generating circuit will produce an output of exactly 27v DC.
The latest module to have this feature is JIM's CDU MkII and it has a mini trim pot to adjust the output voltage from 13v to 27v DC to cater for all different types of solenoid points. 
This module has on-board switches to control the position of the point and each module is designed to be connected to a single point or two or three points that ALL need to be activated AT THE SAME TIME.   You can see the project
HERE.
This is just one way to get around the problem for the moment, but at some point in your plans to produce a large layout, you will need a POWER SUPPLY. You can spend a lot of money on a POWER SUPPLY but Talking Electronics is always aiming to show the cheapest and best way to get something at the lowest cost.

Let's look at what we are talking about:

BENCH POWER SUPPLY
A Bench Power Supply is the name given to a power supply that looks like the following images:

They come in all sorts of arrangements and offer current limiting and output voltages to 35v (or higher) at 1 amp to 10 Amp or more.
But these cost a lot and you can build a similar "instrument" (a piece of test gear is called an INSTRUMENT) for less and since it will be "out of a case" you will be constantly reminded of how it has been put together.

The following project is a 0v to 12v BENCH POWER SUPPLY  with current limiting and has an output of 1 amp. This is sufficient for all types of testing and you can increase the values by referring to the circuit.
The whole idea is to create projects at the lowest cost and have them open for viewing so you can remember how they were assembled.      

Here is a set of 4 Li-ion cells. Just use the 4 lower cells in a 4-cell carrier. The top cell is just to increase the voltage slightly so the project will produce slightly more than 12v at 1 amp.


You can buy Li-ion cells for about $2.50 each on eBay. They have a capacity of about
2 Amp-hour to 3 amp-hour.

The 4-cell carrier can be bought on eBay for about $2.50

The following 4-cell charger can be bought on eBay for about $3.50.
This will charge the cells at about 70mA to 150mA and it will take about 24 hours to fully charge a depleted set of cells. 

The charger below will charge a single cell at about 500mA to 700mA and connects to your USB port on a laptop. You can only charge one cell at a time with this arrangement.



The 1 ohm resistor will discharge the cell quickly. The cell voltage must not go below a minimum voltage of 2.8v. You need to place a voltmeter across the resistor while discharging to make sure you do not discharge the cell below its recommended minimum.  The module in the photo charges the cell quite quickly and at 4.2v the cell is charged to 90% (or more) and the circuit turns OFF.
You must use a charger that turns OFF when the cell is charged as this type of cell cannot be left charging on a "trickle charger" as the cell will produce internal "whiskers" and it will get damaged.

More details of the project shown above can be found HERE.  It describes a 1 amp adjustable POWER SUPPLY that can be used to power your locos or as a BENCH POWER SUPPLY for all your testing. 

CURRENT
How much current do you need?  That is: how many AMPS do you need?
A small loco takes 300mA to 600mA and you need a 1AMP supply to make sure the necessary current can be supplied as the motor will take 800mA to 900mA when starting and accelerating and when hauling a number of coaches.
For a DC layout, you will generally only be running one loco at a time and a 1-Amp supply will be sufficient.
The current values mentioned above apply when the supply is 12v.
If the supply drops to say 10v, the current will be less and if the supply increases to 14v, the current will increase by a considerable amount. It is impossible to state the actual values because
the current taken by a motor increases and decreases due to the load and this load is not only the velocity of the train, but the acceleration and inclination of the track and also the rpm of the motor as it takes more energy to rotate at higher rpm.

CONCLUSION
You need to buy or make 2 POWER SUPPLIES:
16v to 17v  @ 1 amp POWER SUPPLY for a throttle (to drive a loco). (suitable for 1 or 2 locos).
24v POWER SUPPLY for a Capacitor Discharge Unit. (less than 100mA needed)
Cost will less than $15.00 for up to 4 Plug Packs. (see above for details of the Plug Packs you need to buy.
If you build a Bench Power Supply (see
Power Supply MkII) you will have an adjustable output voltage (0v to 12v DC) and you will be able to limit the current (from 30mA to 1 amp) so the project you are testing will not be damaged.

When you have the 2 Power Supplies, you can decide on the Capacitor Discharge Units and the Throttle module.

     to Index

POINTS - TURNOUTS
Talking Electronics makes lots of different modules to change the points in your layout (to suit different voltages and different situations). That's why you have to read ALL this article before making up you mind.
All layouts need a point or lots of points so you can make an impressive layouts and have the the trains leave and enter the main line and provide shunting yards and loops and interconnecting lines.
There are so many choices for a point and so many different expenses that we have simplified everything and created the best control modules on the market at the lowest cost for all the different types of situations.

WHERE DO YOU START?

Start by buying the cheapest left or right hand point FOR MANUAL OPERATION. This is the  version we will convert to either remote or automatic operation.


This is a MANUAL POINT

If you have a solenoid operated point, we will cover it later:
This is a point with a solenoid actuator to move the rails. We will cover this later in the article.

CHOICE NUMBER 1:
All these modules convert a manual point into a remotely controlled point.
There are a number of modules and the differences will be cost, size, and fast or slowing changing of the point.
The first choice is: POINT CONTROLLER using MOTOR and WORM GEARBOX for $25.00
Click
 
Here to order.

We connect a motor and worm gearbox as shown in the following image:


 

and connect the module that controls and limits the motor's operation to a 12v to 16v AC or DC supply.


The module with motor is available from Talking Electronics
for $25.00 including postage.

You get micro motor and module and DPDT push-push switch and the position of the point is shown on the red and green LEDs. The movement of the point is fairly rapid. There are other modules have slow movement.

          oooooooooooooo0000000000000000000000000000oooooooooooooooo

CHOICE NUMBER 2:
In place of the micro motor and worm gearbox shown above, you can use a converted servo, as shown in the following image.

This module is called
POINT CONTROLLER using converted SERVO  for $24.00. 
Click  
Here to order.
 


The activating module comes with a push-push switch and knob, that clicks when pushed and unclicks when pushed again.
The module limits the output arm of the servo to less than 45 degrees
and the position of the point is shown on the red and green LEDs. A length of gold wire is included for the linkage.
The movement of the point is fairly rapid. There are other modules have slow movement.

          oooooooooooooo0000000000000000000000000000oooooooooooooooo

CHOICE NUMBER 3:
This module is called
POINT CONTROLLER using 555 IC  for $18.00. 
Click  
Here to order.
The on-board toggle switch changes the point via a servos fairly slowly and this is the main difference from the other modules.  The servo and gold-wire linkage are included with the module.

The ob-board LEDs show the position of the point.          

oooooooooooooo0000000000000000000000000000oooooooooooooooo

 

CHOICE NUMBER 4:
If you want the servo to move slowly to produce a realistic effect, we have a module called JIM's SLOW SERVO
for $xx0.00 including module, servos and  extension lead.
Click
 
Here to order.

 

 

oooooooooooooo0000000000000000000000000000oooooooooooooooo

 

CHOICE NUMBER 5:
If your layout has a number of points that need controlling, we have a 5 SERVO Controller module that controls 5 servo's separately at very slow action.
This module is called
5 POINT CONTROLLER  for $40.00 including module, 5 servos and 5 extension leads.
Click
 
Here to order.
 

The on-board switches need to be pressed for about 1/2 second for the program to activate the servo and set it to the correct position.

oooooooooooooo0000000000000000000000000000oooooooooooooooo

 

SUMMARY
A manual point costs between $15.00 and $25.00.  The five different modules above cater for all sorts of different requirements and this means a remotely activated point can be added to your layout for as little as $40.00


There are other options, so keep reading:

AUTOMATIC OPERATION
The next thing you will want to do is operate the point
automatically to prevent a derailment when the train enters a point that is incorrectly set.

     to Index

Automatic Point

Automatic Point is available as a kit from:
Talking Electronics for $29.50 incl reed switches
and servo. 
Click HERE for details.

Turn your manually-operated point into an automatically operated point.
Here is a typical turn-out.

You can convert it to an automatic point, with over-ride via two push-buttons and it will cost less than buying a solenoid actuator for the point, plus a CDU module.
AUTOMATIC POINT project comes with 2 reed switches and a motor/gearbox and when the train approaches the point from the siding or via the other rail entering the point, the loco is detected and the circuit changes the point to accept the train. This prevent derailments and saves you having to remember to constantly change the point.
You will have to manually choose when to send the train to the siding.
The project only prevents a derailment when returning.

AUTOMATIC POINT is powered by the track voltage and will operate on a voltage between 9v and 16v DC. It has a 100u storage capacitor to allow the circuit to work when the rail voltage is intermittent.
The servo takes less current and less voltage than a solenoid operated point and that makes it ideal for remote points. You can use thin cable for the wiring.


Turn your manual point into an AUTOMATIC POINT br> When a train comes from direction A or B, the
point gets automatically set to prevent a derailment


Click for large image


There are many ways to position the servo to allow the lever to control the point.
Placing the servo on its side will give better alignment, as shown below:


The servo rotates less than 70 and the gold wire is called the "linkage."
Any electro-mechanical device (motor, solenoid, servo) that operates a point is called a SWITCH MACHINE.
This project will only operate a normal (unconverted) SERVO as the circuit sends PWM signals to the servo to set its angle of rotation.
Talking Electronics has other projects that operate a motor and gearbox or a solenoid, but this project is specially designed to turn a manual point into an automatic point at the lowest cost.
The servo can be placed under your layout or in a plastic model such as a Platelayers Hut.


A platelayers hut can be used to hide the servo

There are many ways to connect the servo to the "switching lever" and here's one way that adjusts the movement of the arm on the servo to the travel needed by the switching lever.
It consists of a machine pin fitted to your layout and another machine pin fitted into it. This forms a  pivot and you can adjust the travel by providing the correct ratio for the gold wire before the pivot and after the pivot.
This arrangement also puts a small amount of tension on the rails, allowing the loco to pass if the point is not set correctly.  

The following images clearly show how the 3.7g SERVO is connected to the point via a LINKAGE:



The Machine pin in the centre of the linkage acts as a pivot and the "crank" in the lever is simply to align the activating arm to the lever on the track.


THE SUPPLY
The supply for this project is 9v to 16v DC - but is is best to deliver a maximum of 12v. A voltage higher than 12v will make the 470R and BC338 slightly hotter.
You can deliver 12v AC as the diode and 100u will convert this to a DC voltage and the BC338 will smooth the output with the aid of the 6v2 zener diode.
Nothing in the circuit is susceptible to a small amount of ripple, so AC input is not a problem.

 
CONSTRUCTION
Assembly of the PC board is straightforward.
Fit the resistors first and then the electros, transistors, LEDs and diodes. The last parts to fit are the terminal blocks and switches.
You will need wiring to a 12v supply and you will need to connect the mini reed switches to the screened audio cable and add metal ends to the wires so they can be fitted to the screw terminals.
All these parts are included in the kit as well as 2 very strong super magnets. These are to be fitted under two locos.


Everything fits neatly on the board


All the components are clearly identified.
 


The two reed switches are carefully soldered to the
leads (very fine screened audio lead).
2 very strong rare-earth magnets
operate the reed switches at 2-3cm
(reed switches separately with 2 magnets cost $4.00)

SETTING-UP THE MAGNETS
The kit comes with 2 x 10mm super magnets about 1mm thick and to get the best magnetism from these magnets, place them on the bench about 5mm apart with one magnet having the North pole up and the other South pole up.
Don't worry yet.   When the opposite poles are up,  the reed switch will activate when it is lowered over the magnets at 10mm distance. If no reaction, flip one magnet over. The response will be dramatic. Now glue the magnets to the underside of a loco with N-pole up and the other S-pole up.
One up and one down creates a circular magnetic path through the "leaves" of the  reed switch and makes one leaf "N" at the tip and the other "S" at the tip and the two leaves click together.

FITTING the REED SWITCHES
Fit the two reed switches near the point but give the servo time to change the point before the loco gets to the point.
Connect the 12v supply and one of the LEDs will illuminate. It indicates the position of the point.
Press the other button and the point will change.  Drive the train through the point (from left to right) and when you return from the siding, the point will be ready for the train.

 

PARTS LIST
Automatic Point
$29.50 including reed switches
and servo. 
Click HERE to buy the kit.


1 - 470R
4 - 1k
2 - 2k2
4 - 10k
1 - 47k
1 - 120k
1 - 2M2

1 - 22n ceramic capacitor
2 - 10u electrolytics
2 - 100u electrolytics
1 - 1N 4148 diode
1 - 1N 4004 diode
1 - 6v2 zener

2 - BC547 transistors
2 - BC557 transistors
1 - BC338 transistor
1 - 555 IC
1 - 8 pin IC socket
1 - 3mm white LED
1 - 3mm blue LED
2 - 40cm lengths twin hook-up flex
3 - 60cm lengths screened lead
2 - reed switches
2 - rare-earth magnets
3 - 2-screw terminal blocks
2 - large push buttons with caps
1 - servo with "arms" and 2cm gold wire
1 - 3-pin 90 male connector for servo
30cm fine solder
1 - Automatic Point PC Board
 

     to Index
SERVOS


There are many different types of SERVOS on the market. Some are very cheap while others are very expensive. The main difference in cost is due to plastic gears Vs metal gears.  We only need plastic gears.
We have simplified the requirement and come to the conclusion that there are two types suitable for controlling a point. The "normal" size is called "9g" and the "Micro" size is called "3.7g." You can see by the dimensions above that the difference is only very slight.
But you have to be careful.
There are many different manufacturers with the same plastic body and the same appearance. Some will work in our applications and some will not. The program in the "electronics" is slightly different.
In some of our projects, we slow-down the rotation of the arm to make the movement "realistic."
All the Micro SERVOS work in this "slow-down" application, but only 30% of the 9g models work successfully  - some jitter when travelling slowly and there is no way to determine the faulty ones without testing each servo.
In addition, some of the 9g models can rotate 360 because there is no "stop" on the output shaft. This is not a problem in any way.
All it means is this: the shaft cannot get jammed against the "end-stop."  You cannot digitally rotate the shaft any more than about 180 to 270, as the electronics is only designed to allow this much rotation. But if you position the shaft at the exact "dead-spot," the servo will not know "which way to turn" and you have to activate it twice and it will swing around to the correct position. Under normal operating conditions, the servo will never land on the "dead-spot" and you will never have a problem.
In all other respects, the two servos are identical. The Micro version is slightly more expensive and ideal for controlling a point as it can easily be housed in a PlateLayers hut. (see image up further)

     to Index

REED SWITCH DETECTION

The reed switch only detects a magnet when the magnet is in  positions A and C.  This is because the magnetic flux produced by the magnet "hits" the left or right reed and magnetises it in a process called TEMPORARY MAGNETISM or INFLUENCED MAGNETISM and since the other reed is not magnetised, the two reeds "stick together." When the magnet is in the centre of the reed, both reeds get magnetised by the North pole of the magnet and they do not make contact.
This means the reed switch MUST be placed "along the track" (parallel with the rails) so the magnet has the greatest opportunity to activate the reed.

     to Index

Hall Device
The Hall Device must be connected the right way to the circuit.
Here is a close-up the Hall device with the output lead connected to the first lead. These two are connected to the white lead of the screened audio cable. The middle wire is the ground connection and it goes to the screening wires. 
This is very unusual way to wire a Hall device, and is just another clever trick by Colin Mitchell to show how you can do just about anything with electronics.


Connecting the screened lead to the Hall device


This is the circuit for the Hall Device

This is just one way to connect it to a circuit when you want to be able to connect a Hall Device or a reed switch to the same input terminals of a project.


Connecting the Hall wires to the module


The internal circuit of the 3144 contains a number of "Building Blocks"

The Hall device is being used in an unusual way in this project, with the output connected to the "supply terminal."
The circuit above shows some of the "building blocks" inside the 3144 and one of the features is the amplifier block that detects a signal from the Hall block to turn ON the output transistor.   Some of the other Hall devices turn-on-slowly as a magnet is brought closer to the detecting face. Make sure you do not use one with this feature, as we have not checked it and it may not turn on hard enough to start the module flashing. The main reason for it not working is the low impedance of the input line (on the Flashing Lights Module) - due to the 220R load resistor.

 
 

CAPACITOR DISCHARGE UNIT
The next item we will cover is the CAPACITOR DISCHARGE UNIT.

The most common type of activation of a point is via a solenoid that moves the rails from one position to the other.
It is also called  a TURN-OUT MOTOR:

It consist of two solenoids that alternately pull a metal rod into the middle of the solenoid and at the same time change the position of the point.
These solenoids have a small number of turns of wire and take a high current when connected to a train power supply. The resistance of the coil is about 4.5 ohms and when connected to 12v, the current will be nearly 3 amps. They must only be activated for less than half a second and if the 12v is connected for more than 10 seconds, the plastic case will start to smell and melt. In a few more seconds the solenoid will be completely damaged.
To prevent this from occurring, you need an electronic module that delivers the current to it for a very short period of time (so that nothing gets warm).
This module is called a CAPACITOR DISCHARGE UNIT and it contains 2 or more 1,000u electrolytic capacitors that deliver the required energy.
These capacitors get charged slowly and when they are fully charged, you can press a switch and operate the point. It does not matter how long you hold the switch because the capacitors are drained in less than a second.
The simplest and cheapest CAPACITOR DISCHARGE UNIT is shown in the following image:


This is CDU MkIIBM  $14.50 plus $6.50   fully assembled

The screw terminals make it easy to fit to your layout.
Here are the connections to the Power Supply and point:

This module fits between a Power Supply and the solenoid on a point. It is designed to deliver a short pulse of energy to the solenoid to change the position of the point.
If you do not include a Capacitor Discharge Unit, you may leave the switch connected to the point for more than 10 seconds and the flow of current will heat up the solenoid and "burn it out." The CDU prevents this.

For layouts that need 2 or more points changed at the same time, a larger version is available with 2 x 4700u electro's:


CDU MkIII fully built and tested $16.50 plus $6.50 postage



Connecting CDU MkIII to 24v supply

Up to 8 points can be changed at the same time with the largest CDU::


CDU Module 18,000 fully built and tested $22.00  plus $6.50 postage

 This Capacitor Discharge Unit is easy to connect to your layout with screw terminals.
You need two push switches to change the position of the point. The LED on the board shows the electrolytics are charged.
SPECIAL FEATURES
Input voltage can be AC or DC. But you MUST use the correct set of terminals. It did not work for one customer because he connected DC to the AC terminals. There is a 100u electrolytic on the AC terminals and "it will not let the DC in."  The 100u is for a voltage-doubling network at the side of the board as shown in the image above. 
Three sets of input terminals are provided.
8v to 12v AC
13v to 20v AC
12v to 30v DC
The project comes with instructions for connecting to a plug pack (wall wart) plus information to connect two plug packs (in series) to get the required voltage.
The CDU 18,000u has zener diode regulation to prevent over-charging.

 

Talking Electronics has produced 8 different modules to operate a point and you need to look at all the different designs before deciding.
If you want to convert a manual point to automatic, 4 of the modules cover this.
The old way to change a point is via a solenoid, but these are expensive and need a CDU to make them reliable and safe from overheating.
The new way is to use a micro motor and gearbox and these change the point slowly and the motor/gearbox and electronics is much cheaper.
One module changes the point automatically and has 3 other features so you can design a layout with one or two loops and a signal.
This module is called: LOOP with 2 RELAYS and MOTOR.
You can use either a 3v micro motor and gearbox or a SERVO or a converted SERVO.
You need to loop at the project and then contact Colin Mitchell for final details of which actuator you want as the program in the PIC micro has to be burnt to suit the actuator. The project also comes with a 2-aspect signal. 

 

 

 

 


We will start with the solenoid POINT CONTROLLER.
This is the most common of all the controllers and consist of two solenoids that pull a metal rod into the middle of the solenoid and at the same time change the position of the point.
These solenoids only have a small number of turns of wire and take a high current when connected to a train power supply. The resistance of the coil is about 4.5 ohms and when connected to 12v, the current will be nearly 3 amps. They must only be activated for less than half a second and if the 12v is connected for more than 10 seconds, the plastic case will start to smell and melt. In a few more seconds the solenoid will be completely damaged.
To prevent this from occurring, you need an electronic module that delivers the current to it for a very short period of time (so that nothing gets warm).
This module is called a CAPACITOR DISCHARGE UNIT and it contains 2 or more 1,000u electrolytic capacitors that deliver the required energy.
These capacitors get charged slowly and when they are fully charged, you can press a switch and operate the point. It does not matter how long you hold the switch because the capacitors are drained in less than a second.
The simplest and cheapest CAPACITOR DISCHARGE UNIT is  shown in the following image:
 




CAPACITOR DISCHARGE UNIT
 
The next item we will cover is the CAPACITOR DISCHARGE UNIT
This is the module that fits between a 24v Power Supply and the solenoid on a point. It is designed to deliver a short pulse of energy to the solenoid to change the position of the point.
If you do not include a Capacitor Discharge Unit, you may leave the switch connected to the point and the flow of current will be very high and either the point will start to heat up or the power supply will be overloaded and "burn out."

Talking Electronics has produced 8 different modules to operate a point and you need to look at all the different designs before deciding.
If you want to convert a manual point to automatic, 4 of the modules cover this.
The old way to change a point is via a solenoid, but these are expensive and need a CDU to make them reliable and safe from overheating.
The new way is to use a micro motor and gearbox and these change the point slowly and the motor/gearbox and electronics is much cheaper.
One module changes the point automatically and has 3 other features so you can design a layout with one or two loops and a signal.
This module is called: LOOP with 2 RELAYS and MOTOR.
You can use either a 3v micro motor and gearbox or a SERVO or a converted SERVO.
You need to loop at the project and then contact Colin Mitchell for final details of which actuator you want as the program in the PIC micro has to be burnt to suit the actuator. The project also comes with a 2-aspect signal. 

 

 


 

Here are two CDU  (CAPACITOR DISCHARGE UNITS) from Talking Electronics:

 

The input voltage needs to be 16v DC to 25v DC and you will need two adaptors in series to get this voltage.

When you have made a 25v power supply for the CDU modules, (to change the points), you will want to make a POWER SUPPLY for a THROTTLE to power your loco's.
Most locos take about 500mA and need a voltage of about 12v for full speed.
For a throttle to deliver 12v, it needs an input voltage of 14v to 16v as about 3v to 4v is lost in the bridge diodes and the electronics.
It is very difficult to get 16v DC from any plug pack, and that's why you need to follow our discussion. 

POINT CONTROLLERS
The next set of projects we will cover are called POINT CONTROLLERS.
A Point Controller is a "device" or "MOTOR" or "SOLENOID" that changes the point from "ahead" to "Siding."
The ACTUATING MECHANISM can be  double-acting solenoid to move the rails from one position to the other. Alternately this can be done with a motor and gearbox or a micro motor and gearbox or a SERVO or even a LINEAR ACTUATOR. These all come in different sizes and at different costs.
We will now cover the 6 different projects from Talking Electronics, including the cost of the electronics.

The following image is a typical manual point. The spigot is moved sideways to alter the position of the rails.


A Manual Point that will be converted to remote operation by the projects described below:


In the following projects we will cover projects that convert a MANUAL POINT into an AUTOMATIC POINT (or remotely controlled point).
All these projects are cheaper than getting a solenoid for the point shown above and adding a CDU module.
In place of the solenoid, these projects use a SERVO or MOTOR and GEARBOX or a MICRO MOTOR and GEARBOX.
And some of the projects include additional features such as automatic operation of the point and reversing the voltage to the track so that loops can be included in your layout.
You have to go through each of the projects carefully and work out the features you want.   



TRAIN THROTTLES
There are a number of different TRAIN THROTTLE circuits.
The type(s) we are considering need either AC or DC input and produce 0v to 12v DC output.
If you have an AC supply 10v AC to 12v AC, the Throttle Circuit below will produce an output of 0v to 12v DC - that is what it is designed to do.
If you have a 12v DC supply, the voltage drops across the input power diodes and the control circuitry, will reduce the output to about 10v DC.  You can lose up to 2v DC.
This means you need an input voltage of 14v DC and this will require 2 adaptors in series or a set of 4 Li-ion cells.
The following project uses 4 Li-ion cells to provide a voltage of about 14.2v DC to 14.8v DC and this is ideal for many types of TRAIN THROTTLE.

There are two types of TRAIN THROTTLE:
Type1 produces an output 0v to 12v DC and you need a reversing switch to reverse the train.
Here is the circuit and photo of the completed project and the wiring for the reversing switch:


 
Two Amp Power Supply circuit diagram.
The ammeter is also included in the kit



The completed POWER SUPPLY, showing the placement of the parts
The input voltage can be AC or DC. 
The DC voltage needs to be at least 16v6 to get 12v DC out. If you supply 17v to 20v DC, nothing will be damaged.  Just the 470R resistor will get slightly hotter.

The 2-Amp POWER SUPPLY project is HERE
Kits come with 0-2 Amp meter to show the current.
$12.50 USD plus $6.50 USD postage.


You will need a double-pole double-throw toggle switch to reverse the train. Ask for it.  $2.50 extra.



Here is a set of 4 Li-ion cells. Just use the 4 lower cells in a 4-cell carrier:


You can buy Li-ion cells for about $2.50 each on eBay. They have a capacity of about
2 Amp-hour to 3 amp-hour.

The 4-cell carrier can be bought on eBay for about $2.50

The following 4-cell charger can be bought on eBay for about $3.50.
This will charge the cells at about 70mA to 150mA and it will take about 24 hours to fully charge a depleted set of cells. 

The charger below will charge a single cell at about 500mA to 700mA and connects to your USB port on a laptop. You can only charge one cell at a time with this arrangement.



The 1 ohm resistor will discharge the cell quickly. The cell voltage must not go below a minimum voltage of 2.8v. You need to place a voltmeter across the resistor while discharging to make sure you do not discharge the cell below its recommended minimum.  The module in the photo charges the cell quite quickly and at 4.2v the cell is charged to 90% (or more) and the circuit turns OFF. This is very critical.
You must use a charger that turns OFF when the cell is charged as this type of cell cannot be left charging on a "trickle charger" as the cell will produce internal "whiskers" and damage the cell.

The second type has a throttle control with 0v in centre-position and "left" reverses the train at a gradual increase and "right" drives the train forward at an increasing velocity. No change-over switch needed.
This type of Train Throttle can be PWM and provides pulses of energy. This design "kicks" the motor and allows it to start the train very slowly. The "kicks" are very rapid and sometimes you can hear the "buzz" from the motor.
All these circuits require an input voltage of 14v DC, so the full 12v DC can be delivered to the motor (as up to 2v DC is lost in the circuitry).


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TEST EQUIPMENT
LED TESTER
This project tests LEDs and tests for continuity and tests for other things as well.
It's a very handy piece of test gear.
See the full project HERE


The LED Tester Project


The 3 button cells are held in place with narrow heatshrink
after soldering fine tinned copper wire over the cells.
You can then cover the cells with duct tape.

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TEST EQUIPMENT
TRACK TESTER
This project tests the voltage on your track.
It's another very handy piece of test gear.
See the full project HERE
The Track Tester kit costs $10.00 AUD plus $4.50 AUD postage.
The Track Tester is also available ready-made for $16.50 USD (posted)
It alerts you to the presence of DCC via the piezo diaphragm and the voltage of your track at all parts of the layout. 


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FLASHING RAILROAD LIGHTS
This circuit flashes two red LEDs for a model railway crossing.
 
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FLASHING LIGHTS FOR MODEL RAILWAY CROSSING:
A flashing LED is used to create the timing for the flash-rate and the transistor provides the alternate flash for the second set of LEDs. The first circuit comes off the web, but Colin Mitchell doesn't think it will work. See his circuit below.

The top two 1k resistors are current-limiting resistors and can be increased if you want the LEDs to be dull.
The 2k2 makes sure the two LEDs are completely turned-off because the flashing LED draws a small current when it is off and this shows in the two LEDs. The lower 1k may need to be reduced to 470R to completely turn the transistor OFF. The other circuit does not have any of these features. The flashing LED has to be an ON-OFF flashing red OR green LED.  Not a red-green flashing LED or a RED-GREEN-BLUE flashing LED. The flashing LED actually has an in-built resistor and will work on 2v to 5v. But we are using its feature of "taking a small current" when illuminated and then "taking almost zero current" when not illuminated, to "switch the transistor."  
You can get the CROSSING LIGHTS plastic mouldings from Talking Electronics. They will take 3mm LEDs.
Cost: $6.00 for 2 Crossing Lights with 4 LEDs and 2 metres of fine 0.25mm enamelled wire.
You need to "push-out" the red lens and fit the 4 x 3mm red LEDs and carefully solder wires to the LEDs.

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TRAFFIC LIGHTS
Here's a clever circuit using two 555's to produce a set of traffic lights for a model layout.
The animation shows the lighting sequence and this follows the Australian-standard. The red LED has an equal on-off period and when it is off, the first 555 delivers power to the second 555. This illuminates the Green LED and then the second 555 changes state to turn off the Green LED and turn on the Orange LED for a short period of time before the first 555 changes state to turn off the second 555 and turn on the red LED. A supply voltage of 9v to 12v is needed because the second 555 receives a supply of about 2v less than rail. This circuit also shows how to connect LEDs high and low to a 555 and also turn off the 555 by controlling the supply to pin 8.  Connecting the LEDs high and low to pin 3 will not work and since pin 7 is in phase with pin 3, it can be used to advantage in this design. 
Here is a further description of how the circuit works:
Both 555's are wired as oscillators in astable mode and will oscillate ALL THE TIME when they are turned ON. But the second 555 is not turned on all the time!
The first 555 turns on and the 100u is not charged. This makes output pin 3 HIGH and the red LED is not illuminated.  However the output feeds the second 555 and it turns on.
Output pin 3 of the second 555  turns on the green LED and the second 100u charges to 2/3 rail voltage and causes the 555 to change states. The green LED goes off and the orange LED turns on.
The second 100u starts to discharge, but the first 100u is charging via a 100k and after the orange LED has been on for a short period of time, the first 555 changes state and pin 3 goes LOW.
This turns on the red LED and turns off the second 555.
The first 100u starts to discharge via the 100k and eventually it changes state to start the cycle again.
The secret of the timing is the long cycle-time of the first 555 due to the 100k and the short cycle due to the 47k on the second 555.
 
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4 WAY TRAFFIC LIGHTS
This circuit produces traffic lights for a "4-way" intersection. The seemingly complex  wiring to illuminate the lights is shown to be very simple.
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 4-Way Traffic Lights

 Kits are available for this project from
Talking Electronics for $20.00 for the parts and PCB plus
$5.00 for each overhead light (4 needed) plus $6.50 postage.
The project is also available fully assembled and tested for $25.00 plus postage.

This project adds realism to your layout with functioning traffic lights at an intersection.
You can use column signals or overhead signals.
The PC board shows the condition of the lights and you only need to extend leads from the board to the signals, to complete the project.
The supply MUST be 12v as the voltage of the LEDs adds up to about 10v and any voltage below 12v will not allow some of the LEDS to illuminate AT ALL - and you will think the project is faulty.

 


This image shows how to connect the very fine wires from the end of the post to the screw terminals. The kit contains fine screened lead and two of these leads are used for each overhead signal to the terminals. Two overhead signals are joined in parallel to the first set of four screw terminals and two overhead signals are connected to the second set of four screw terminals.
 

This wiring diagram shows how the LEDs are connected in the over-head light. All the anodes are connected to the black wire and the cathodes emerge as Green, Orange and Red. The 4-screw terminal block is looking at the where the wires enter the terminals and this is clearly shown in the photograph above.

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MODEL RAILWAY TIME
Here is a circuit that will convert any clock mechanism into Model Railway Time.
For those who enjoy model railways, the ultimate is to have a fast clock to match the scale of the layout. This circuit will appear to "make time fly" by turning the seconds hand once every 6 seconds. The timing can be adjusted by changing the 47k. The electronics in the clock is disconnected from the coil and the circuit drives the coil directly. The circuit takes a lot more current than the original clock (1,000 times more) but this is one way to do the job without a sophisticated chip. 

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REVERSING A MOTOR-4 (see 1, 2, 3 in 200 Transistor Circuits)
In this example the power is applied via the start switch and the train moves to the away limit switch and stops. The 555 creates a delay of 1 minute and the train moves to the home limit and stops. Turn the power on-off to restart the action.

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THE CDU  (Capacitor Discharge Unit)
TALKING ELECTRONICS has produced a number of CDU projects and they all have slightly different features. They all supply a lot of energy to a POINT MOTOR for a short period of time and this prevents the Pont Motor getting hot.
Some of the CDU's have LEDs on the PC board that show the position of the point and others control up to 4 points.
Approximately 2,000u is needed to activate the solenoid to change the point and some projects have 2 x 1,000u to meet this requirement.
One project has 2 x 4,700u and this CDU will activate 2 - 5 points at the same time.
Our largest CDU has 4 x 4,700 and is called 18,000u. This is for a very large layout.
Talking Electronics also produces a remotely controlled CDU for a point that is distant from the control panel. It takes a small amount of current from the track to charge 2 x 1,000u capacitors and does not need any wiring back to the control panel. The transmitter is 315MHz and the receiver detects a coded signal to activate the point. The project comes with 1, 2 or 3 remotely controlled CDU's.
Two more projects use a servo to activate the point and this is similar to the Turtle Point Controller.
Our project is cheaper and easier to install as you don't have to get under the layout to install the controller.
One project is remotely controlled and the other uses a toggle switch. There are three versions of this using different switches.

LET's START AT THE BEGINNING  with an explanation:

Here is a diagram to show a CDU is connected to a Point Motor:

A Point Motor is a double-solenoid as show in the image below.
It is also called  Side Mounted Turnout Motor.
It is also called a double-acting solenoid because it will both PUSH and PULL.
The "core" or "plunger" is not a magnet and it will only PULL into a solenoid. The solenoid will accept AC or DC and it can also be called an ELECTROMAGNET.
Because an electromagnet only "pulls," you need two to produce PUSH and PULL motion.  It is really PULL-PULL motion. The core only PULLS into a solenoid.
That's why you need 2 coils.
But the problem is the coils have very low resistance.
If you operate them from the 12v train supply or the 16v AC supply from the train transformer, they will take more than 3 amps and produce a more than 30 watts of heat.  This is equal to a small soldering iron and it will quickly melt the plastic case.
You need to use a switch that only delivers a voltage (and current) to them for less than 1 second. This is called a PASSING SWITCH or a "spring return toggle switch" with a centre-off position.
If you use this type of switch carefully, the operation will be successful. But if you have visitors working the control panel, they may leave the switch ON or work it very slowly and it can cause the solenoid to heat up.
To prevent any of these catastrophes, we have designed a number of CDU - CAPACITOR DISCHARGE UNITS to operate the points safely.
 

Here is a list of the 7 CDU projects from Talking Electronics

 
 
 
 
 
 






Talking Electronics also has projects that convert a manual point into a remotely controlled point. (This is a point that does not have a Turnout Motor ).
The movement of the rail is done with a servo and this is a cheaper alternative to buying a point motor and CDU unit.

The image on the left is just an example to show the connection of the servo to the point. The servo can lay down and take up less room.

 

 

 

 

 



The servo moves the track via the springy-brass wire. The servo is controlled by the project to have less than 90 movement and the project reverses the servo.

Talking Electronics has 3 projects using a servo to control a point.
All the projects are easy to install and you don't have to get under the layout or create any cut-outs.
The following set of projects covers some of the kits available from Talking Electronics.
More kits are listed on the front index of Talking Electronics website and more projects are being developed.

 

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CAPACITOR DISCHARGE UNIT MkII  (CDU2)
This project is available as a kit for $10.80 plus $6.50 post. email Talking Electronics for details.













This circuit will operate a two-solenoid point-motor and prevent it overheating and causing any damage. The circuit produces energy to change the points and ceases to provide any more current.  This is carried out by the switching arrangement within the circuit, by sampling the output voltage.
If you want to control the points with a DPDT toggle switch or slide switch, you will need two CDU2 units.

HOW THE CIRCUIT WORKS
The circuit is supplied by 16v AC or DC and the diode on the input is used to rectify the voltage if AC is supplied. If nothing is connected to the output, the base of the BD679 is pulled high and the emitter follows. This is called an emitter-follower stage. The two 1,000u electrolytics charge and the indicator LED turns on. The circuit is now ready.
When the Main or Siding switch is pressed, the energy from the electrolytics is passed to the point motor and the points change. As the output voltage drops, the emitter-follower transistor is turned off and when the switch is released, the electrolytics start to charge again.



The point-motor can be operated via a Double-Pole Double-Throw Centre-Off toggle switch, providing the switch is returned to the centre position after a few seconds so that the CDU unit can charge-up.

 

 

The Capacitor Discharge Unit can also be purchased with screw-terminals for the input and output leads:

See the full article: HERE

 

CDU MkIIB with 2 x 2,200u electrolytics and screw terminals
$12.50 plus $6.50 postage.  
Click HERE for details

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CAPACITOR DISCHARGE UNIT MkII  (CDU2) -  modification
If your transformer does not supply 15vAC to 16vAC, you can increase the input voltage by adding a 100u to 220u electrolytic and 1N4004 diode to the input to create a voltage doubling arrangement. You can also change one or both the 1,000u electrolytics for 2,200u. This will deliver a much larger pulse to the point-motor and guarantee operation.

 

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POINT MOTOR DRIVER
One of the first things (you will want) when expanding a model railway is a second loop or siding.
This needs a set of points and if they are distant from the operator, they will have to be electrically operated. There are a number of controllers on the market to change the points and some of them take a very high current. (You can get a low-current Point Motor).
The high current is needed because the actuating mechanism is very inefficient, but it must be applied for a very short period of time to prevent the point motor getting too hot.
Sometimes a normal switch is used to change the points and if the operator forgets use it correctly, the Point Motor will "burn-out" after a few seconds.
To prevent this from happening we have designed the following circuit. It operates the Point Motor for 5mS to 10mS (a very short time) and prevents any damage.
You can use a Peco switch (PL23 - about $10.00!!) or an ordinary toggle switch (change-over switch - SPDT - single-pole double-throw).
You can connect to either side of the Point Motor and both contacts of the other side go to 14v to 22v rail.


Point Motor mounted
under the track.


The Point-Motor shaft moves left-right to change the points.


Wiring a Point Motor


Point Motor connected to track


See the full article: HERE

CDU with SPDT switch
$13.50 plus $6.50 postage.  
Click 
 HERE to buy kit

Here is a video showing a point motor connected to a set of points, from the Rail Video Channel:
http://www.youtube.com/watch?v=aW67CFSWGzU&feature=related
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MAKE YOUR OWN POINT MOTOR using a SERVO
Point Motors can be expensive. You can save over 75% by making your own.
Point Motors (or switches) are also known as Turnouts or Points.
A point Motor can be made from an RC Servo (Radio Control Servo).
 


Servo and Horns


Connecting the push-rod


Mounting the Servo on a bracket


Fitting the Servo to the track

All servos come with a variety of attachments for the output shaft. These are called "Servo Horns" or "Servo Arms" and are "single leg horn, (or servo arm), double servo horn, circular horn (wheel) and others.
They convert circular motion into straight-line motion with the aid of a push-rod.
That's exactly what we want, to move the track-rails.  Any of the horns can be used for this project as you only need a very short travel. The push-red needs to be spring-steel and you can unwind a small spring to get this item. 
Servos have 3 leads. Positive, Negative and Signal. The Signal wire is connected to a PC board containing a chip that detects pulses to activate the motor. We do not need this feature.  The PC board needs to be removed. Open the servo and remove the PC board and signal wire. The pot can be left in position but the wires need to be removed.
The two remaining leads are connected directly to the motor.
Our circuit drives the motor and gearbox with a short pulse of energy to provide clockwise or anticlockwise movement.
No limit switches are needed because the railway track provides the limits-of-travel and the motor effectively stalls when the end-of-travel is reached. The gearing produces adequate torque (or effort) to move the rails and a current of about 50mA is sufficient to operate the motor to provide this effort.


See the full article HERE

Point Controller
for Motor/Gearbox
PARTS LIST 
$15.50 plus $6.50 postage.  
Click 
 HERE to buy kit

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TRAIN THROTTLE
This circuit connects an AC transformer (or a DC supply) to a track to provide a voltage from 0v to max voltage (depending on the voltage of the transformer). 
The transformer can be AC or DC and any voltage from 12v to 18v.
The throttle handle connects to the 1k pot.
The diode on the output protects the transistors from reverse polarity (if  another controller is also connected to the rails).
The circuit is limited to about 1amp due to the 1N4004 diodes.

Transformer with 12v AC output and 18v AC

An impressive throttle handle

 
                        Train Throttle Circuit
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OVER CURRENT DETECTION
Requested by William Hicks:
This circuit detects when the tracks are overloaded by too many trains.

Note:  Each 1R resistor needs to be 0.5watt   0R22 needs to be 5watt!!
The circuit will drop 1.4v when full detection-current is flowing.

Here is the simplest over-current circuit:



The reed switch closes when about 1.5 amps flows for 3 turns wrapped around the centre of the reed switch. 2 turns will detect about 2 amps.
Keep the reed switch at least 6cm from the mechanical buzzer as the magnet inside the buzzer will turn the circuit ON all-the-time.
You cannot get a simpler circuit and it creates no voltage loss to the circuit it is detecting.

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Arc Welder Simulator
This project adds reality to a work-site. It produces realistic flickering from an arc-welder.
The full project can be viewed HERE.  A full kit is available from Talking Electronics  for $21.50 plus postage.

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27MHz link for about $10.00
These two modules are available from Talking Electronics for about $10.00 plus post.
They produce 2-channel transmission and can be used for all sorts of communication on your layout.
You may want to control something at the far-end and running cables may be practically impossible.
Or you may want to control something that moves around the layout.
This is an ideal way to solve the problem.
The range is about 10 metres.
The modules come with whip antennas.
See more of this project: HERE


Note: Only one motor is connected to the chip.


The two outputs can be used to reverse a motor or each output can be used to turn on a device.
When there is no transmission (reception) both outputs have zero volts.
For Forward, one output goes high and the other goes low.
The voltage lost across the output FETs is only a few millivolts (about 3 to 5mV).
The output FETs can handle about 200mA to 300mA. 
Each output can be used to turn on a separate motor:

You don't have to buy these modules. You can use the transmitter/receiver from a toy car that no-one wants any-more. (some of them are 4 channel). 
You can operate sound modules, lights, gates, points and anything up to 6v and 200mA. 
Every module is different with different circuitry and chips. This article is just to give an approximate idea of how to use the modules. 


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TRACK PICK-OFF
Track Pick-offs are available  from Talking Electronics for $2.00 plus postage.

This Printed Circuit board is fitted between the sleepers and has contacts to touch the rails so the voltage on the track can be monitored or delivered to a project.
If the current taken from the track is very small, it will not interfere with the operation of the train(s) on the layout and is called LEACHING.
A little bit of power is taken from the track and this saves running wires all the way back to your control panel.
Talking Electronics has designed 2 of these TRACK PICK-OFF boards:

Track Pick-Off MkI has two track joiners soldered to the board and this is fitted between two sections of your layout.
The images below show this board and how it it fitted to the track: 


Twin lead or screened lead can be used for the
Track Pick-off PC board

Here is the module connected to a project:

If it is not easy to connect the track joiners to your layout, we have:

Track Pick-Off MkII.  It has two springy clips that touch the inner parts of the rails
and make electrical contact.
The board comes with the two clips soldered in place and you need to remove the plastic from between two sleepers to allow the board to fit. Twist the board into position and give the spring clip a twist with a pair of pliers so it pushes against the rail.

 

 

     to Index

Jim's Crossing Lights MkIV


 Kits are available  from
Talking Electronics for $15.00 plus $4.50 postage.
See the FULL PROJECT HERE with more details of the Hall Device
 

This project operates crossing lights automatically when the train enters the crossing and turns them off automatically. The flash-rate can be adjusted as well as the brightness of the lights and the overall length of time for the flashing. No other module on the web offers these features.

Two LEDs on the module indicate when the lights are flashing and the module comes with 4 extra LEDs for those who have bought crossing signals without the LEDs installed. 


Jim's Crossing Lights MkIV circuit

The circuit has a number of very clever features.
It uses two 555 ICs to provide all the functions. The signal diode on the first 100u discharges the 100u quickly when the circuit turns off so the timing can restart again with full duration.
The flash-rate can be adjusted because everyone says "the flash-rate is not right."
The "duration of the event" can be adjusted to suit your layout. 
The brightness of the LEDs can be adjusted to suit the type you are using.
The circuit will take 12v DC as the ideal voltage. Do not go below 10v DC as the voltage drops across the various components gives the second 555 less than 5v because the power diode drops 0.7v, the 47R drops about 1.5v and the first 555 outputs a voltage and current via pins 3 to the second 555 for all the rest of the circuit. There is about another 1.5v drop in doing this.
The circuit will work perfectly up to 15v DC and when you supply a DC voltage higher than 15v, the 15v zener comes into action and any voltage above 15v, will be dropped across the 47R resistor. If you supply 16v, the voltage drop across the resistor will be 1v and the current that will flow through the 47R will be
I=V/R =  1/47 = 20mA. This current will also flow through the 15v zener and is called the REGULATION CURRENT or wasted current and the wattage dissipated by these two components will not be noticed at the moment. But if the supply voltage is raised to 20v, the "wasted current" will be 100mA and the wattage dissipated by the 15v zener will be 15 x 0.1 = 1.5watts. The zener is 1watt and it will burn out at 1.5watts, so the limitation of input voltage is 18v.
The zener in this circuit is NOT called a zener regulator but a ZENER LIMITER.   It prevents voltages higher than 15v because the 555 IC's are limited to 18v operation. 
The circuit is designed to take either two reed switches OR two Hall effect devices (switches).
The Hall switches are connected in a very clever way. They are connected so that they sit with a load resistor of 220R and due to the small current they require, the voltage at the "pick-off" point is about 9v for a 12v supply.
When any of the input devices detects magnetic flux, the circuit switches ON and the output lead effectively goes LOW. The voltage goes to 0v for the reed switch, but the Hall device is different. This "pulls" the "pick-off" point lower and as it gets lower, the voltage to the Hall device drops too. As the voltage across the device reduces, its capability to keep the output low is reduced and thus the output does not drop to 0v, but stops at about 2-3v. At this voltage the device is still working and pulling the output as low as possible, (with the current that is available at this low voltage).
You can combine one reed and one Hall device as the 220R will cover the requirement of either/both devices.    
The voltage at the "pick-off" point is detected by Pin2 of the 555. This pin only detects a LOW and when the voltage drops to 33% (or less) of the voltage on pin 8 of the chip, it starts to "time the event."
The timing of the event is done by charging a 100u via a resistor(s) and when Pin6 detects 66% of the voltage on the Pin8, the output Pin 3 goes HIGH and the project turns OFF. The only component taking current when the project is not flashing, is the first 555 and this takes up to 10mA. 
To reduce the brightness of high-brightness red LEDs, it takes up to 10k via a mini trim pot. This will allow all different types of LEDs to be used.


Everything is identified on the PC board  

The module is available fully-built and only needs to be connected to 12v DC. Connect the reed switches or Hall devices to the input terminals and switched ON.
Bring the magnet up to the reed switch or Hall device and work out the distance at which it is detected.
The magnet must be around the correct way for the Hall device as it detects just the North or South pole, according to the way the Hall device is placed.
The detection range is about 5mm for the tiny super-magnets we supply in the kit
This will help you place the reed switch or Hall device in the centre of the track and glue the magnet under the loco, and have the gap small enough to make sure the circuit responds every time. 

CROSSING LIGHTS
There are many different types of crossing lights and most of them have three wires.
The black and red wires are shown in the diagram below. 


The Crossing Light above is available from Talking Electronics for $5.00
You will need 2 of these.  (HO scale)


This crossing Light is on eBay


Jim's Crossing Lights
$15.00
plus $4.50 postage
Kits are available

1  - 47R   all 0.25watt
1  -  220R
2  -  1k
1  -  2k2
2  -  4k7
1  -  10k
1  -  100k
2  -  10k mini trim pots
1  -  100k mini trim pot

3  -  100u electrolytic

1  -  1N4148 diode
1  -  1N4004 diode
1  -  15v 1watt zener diode
6  -  3mm red LED

2  - 555 ICs
2  -  8 pin IC socket 
1  -  BC547 transistor

2m  -  2-core cable for input devices
2  -  mini reed switches  or
2  --  Hall effect devices
2  -  10mm x 1mm super-magnets
1  -  2-way terminal block
2  -  2 pin sockets - round pins
2  -  4 pin sockets - round pins (called
                                machine pins)
1  -  mini slide switch
1  -  20cm very fine solder 

1  - Jim's Crossing Lights MkIV PCB

You will need 2 x Crossing Lights as
shown in the images above
 

     to Index

Jim's CDU MkII


Home

Buy a kit: 
Jim's CDU MkII
$24.50 plus $6.50 post

 
Don't worry about the names for these projects. They are all give different names so I can remember what they do and get them ready for sale.
It's much more intelligent than calling the project MBF-23A- 476  !!
Who is going to remember this number in 10 year's time !!!  

This project combines a number of features from three of the projects we have previously designed and sold to Model Railway Hobbyists.
Now you can get all these features in one module.
The first feature is the power supply. This module connects to your track and you don't have to provide 15v AC or a higher voltage to charge the electrolytics. The module has an on-board charging and voltage generating section that accepts almost any voltage and charges the electrolytics to a maximum of 27v.
The next feature is the variable voltage (or maximum voltage) for the electro's. You can reduce the voltage to as low as 13v for those solenoid points that do not need a large amount of energy for their activation.
The third feature is the reed switch inputs. This allows the module to be used automatically to control a solenoid point so the point gets changed correctly when the train approaches from the other direction.
And lastly, the kit comes with a TRACK-PICKOFF MkII connector that fits between the sleepers and connects to the rails with springy connectors.     

THE CIRCUIT
All the work is done with the microcontroller.
The charging of the electro's, the timing to activate the solenoid and the detection of the reed switches.
The rail voltage is passed to the project via a bridge and this allows AC DC or DCC to be converted into DC and stored to a small extent in the first 100u. The 100u on the output of the 78L05 provides a small amount of reservoir for the micro and we are assuming the train will be moving most of the time to maintain supply for the micro.
The micro drives a BC 338 transistor with short pulses to allow current to flow into (through) the inductor and produce magnetic flux. When the transistor turns OFF, the magnetic field collapses and produces a very high voltage spike. This spike passes through the high-speed 4004 diode and into the 4,700u electros. The spike is really about 50v but the energy in the spike is converted into charging current and the electros would charge to more the 40. But they will explode if the voltage rises above 30v so the voltage on the electros is monitored by the 100k resistor and 10k pot.
The PIC micro detects a HIGH when an input is 2.2v and the 10k pot can be adjusted produce a voltage from 13v to 27v.
The project takes a very small amount of energy from the track during the charging process and this will not be noticed when powering a train around the layout.
The indicator LEDs on pins 2 and 5 are output devices as GP2 and GP5 are constantly changed from input to output lines. They normally illuminate one of the LEDs, but every 100mS, the program converts the lines to input to detect if a reed switch has been activated.  
When they are input lines, we want them to have 0v on them and the 10k resistors across the LEDs provide this feature. Without the 10k resistors, the impedance of the LEDs is very high and the input lines can "float" and if a white LED is used as an indicator, this "float" voltage can be as high as 3.3v. The micro sees any voltage above 2.2v as a HIGH and the circuit would not work correctly.
If a reed switch is activated, the line will be HIGH and the program will respond accordingly.


SOLDERING THE KIT
Soldering these kits is very simple for me as I build them 10 at a time and have a very good soldering iron and 0.5mm solder THAT IS NOT CHINESE SOLDER. Do not use Chinese solder as it does not contain the correct percentage of tin and lead and it does not "run" or melt or flow properly and does not produce a shiny joint.
I can't use Chinese solder so you will definitely not be able to use it.
The first things you add to the board are the 13 surface mount resistors. Add a small amount of solder to one land for each resistor and pick them up with tweezers with the numbers showing and solder one end with the solder that is already on the land. Then go around and solder the other ends by adding a small amount of solder to each resistor.
The rest of the components are through-hole and it does not matter if you start at one end of the board or with the small components first.
Every component is identified on the board and most of the parts have to be fitted around the correct way - so look at the legend on the board.
The LEDs must be soldered very quickly otherwise they will be damaged.
The mark of a well-designed PCB is being able to put it together with a handful of parts and no other reference.
And the mark of a well-designed circuit is 100% operation with every board. You cannot afford to be messing around, "adjusting" the component values and trying to work out why it does not work. 
That's why every value has a reason and a purpose. This can only be gained by working on hundreds of circuits and gaining the experience, knowledge and understanding. 
The circuits are provided with all the projects to give you this experience.
And to help you fix something, if it "blows up."



 The photo's above show the complete module (before all the leads are connected). The electro's will be bent over and laying flat above the top of the board on modules pre-built and posted through the mail as they are too tall to be posted.
 
POWER CONNECTOR
The power for this project can come from a power supply 9v to 15v AC or DC or DCC. In fact it can be ANYTHING !!
You can also connect the project to the track with a very small THIN PC board that fits between the sleepers. It is called Track Pick-Off MkII.  It has two springy clips that touch the inner parts of the rails and make electrical contact.
The PC board comes with the two springy clips soldered in place and you need to remove the plastic from between two sleepers to allow the board to fit (as shown in the photo below). Twist the board into position and give the spring clip a twist with a pair of pliers so it pushes against the rail.


A close-up of the springy gold wires and the
fine screened lead

 

Jim's CDU MkII
PARTS LIST
$24.50 plus $6.50 post
Order a kit

1 - 22R  surface mount
2 - 100R
1 - 220R
2 - 1k
3 - 2k2
1 - 5k6
2 - 10k
1 - 100k

1 - 100k mini trim pot

1 - 100n monoblock
1 - 22u
2 - 100u
2 - 4,700u 25v electrolytics

4 - 1N4004 power diodes
1 - UF4004 high speed 1amp diode

1 - 78L05 5v regulator
1 - BC338
2 - BD679 transistors
1 - PIC12F629 micro with "JimCDU"

1 - 3mm red LED
1 - 3mm green LED
3 - 2-way screw terminal blocks
1 - 3-way screw terminal block
1 - slide switch
2 - tactile switches
1 - 10mH choke

1 - 8 pin IC socket
30cm very fine solder

1 - Jim's CDU MkII PCB

extras  $4.50:

2 - 2-way screw terminal blocks
2 - reed switches
2 - super-magnets
2 - 1.2m screened lead for reed switches
1- Track Pick-off MkII PCB with springy connectors
1m - fine screened power lead for above
2 - tactile switches for remote operation
1 - PCB to mount the 2 tactile switches
1 - 3m flat lead for switches (4 core)

CONCLUSION 
This is a very interesting project to convert a solenoid operated point into semi-automatic operation by adding the two reed switches so the train will set the point correctly when entering the point from the opposite direction.
The module shows the position of the point via a red and green LED and it's very easy to set-up with the Power Connector and extension switches.

 

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These two c

 

 
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                 to Index
If 3rd band is gold, Divide by 10
If 3rd band is silver, Divide by 100
(to get 0.22ohms etc)
 

25-2-2019  Colin Mitchell   

You can copy and use anything for your own personal use.
Direct copying to other websites is not allowed as these projects are updated and too many 
websites have copied my eBooks and not given credit to me.