Kits: Crossing Sound MkII
US$26.50 plus $6.50 post

2 x Crossing Signals
and 2 Boom Gates $8.00
Total: US$41.00 incl postage

This is what you get:

We also have a kit to detect the presence of IR from the IR diodes.
It detects 38kHz IR signals and  constant IR signals. 
See IR Detector kit: $5.00

We also have a LED TESTER kit
and LOGIC PROBE kit to help with testing your projects

This project is designed for a model railway layout.
It provides flashing lights as well as a boom gate bell-sound.
And it is AUTOMATIC.
It is activated by an Infrared Beam and receiver IC that has been placed on a small, narrow PC board fitted between the tracks at a distance from the crossing. Another is fitted at the other side of th crossing about 1 -2 metres from the crossing. The front of the train breaks the beam and activates the circuit. A train in either direction will activate the project.
The circuit waits for a beam to be broken and this produces a HIGH on the input to the microcontroller via an "OR" gate in the circuit. The outputs of the IR detectors are LOW when detecting a beam and when a beam is cut, the output goes HIGH. The diodes in the circuit allow this to take place.  In other words th circuit is an "active HIGH" OR-gate.
When the loco passes the other beam it is broken by the front of the train and the sound stops.
The project is then reset and is ready for a train in either direction. All this is done by the microcontroller.
Talking Electronics also has a project to operate a set of boom gates via a slow-acting motor and gearbox to give reality to the activation. The project does not have sound. See BOOM GATES project HERE.


The project works on TIMING.
The project waits for a beam to be broken and the SOUND AND LIGHTS are activated.
The project produces LIGHT AND SOUND for 5 seconds and then looks to see if the full length of the train has passed the beam. LIGHT AND SOUND continues to be emitted.
The circuit then looks for a second "broken beam" to stop SOUND AND LIGHTS.
This is how the circuit determines the train has passed from one beam to the other.
If you stop the train or delay it or run 2 trains in succession, the timing may not respond correctly. 

Producing a decaying note with resonance is not an easy task with a microcontroller. We have produced the basics of the tone with a program and used two transistor stages to get the decay.
This results in a ding-ding-ding-ding-ding.
At the same time the two LED flash alternately at a low rate.
We have used IR detectors because the level of light varies from one layout to another and sometimes sunlight enters the room.
This changes the ambient light conditions enormously and fluorescent tubes have an effect on normal light sensing devices. 
Adding 38kHz coding to the Infrared transmission eliminates any interference and makes the project very reliable.

A project is available to detect the presence of signal from the IR diodes  IR Detector.
You can detect the presence by looking at the diodes with a digital camera, but this will not let you know if the LED is pulsing at 38kHz.
The IR DETECTOR kit has two circuits and by moving the detector closer to the IR LED, you can see if the emission is bright enough to be detected by the CROSSING SOUND MkII Project. We don't want the LED to be too bright as the wrong receiver will pick up the signal. And we don't want the LED to be too dull or the project will not work. That's why we have used fairly weak LEDs and put a cover over them to concentrate the beam to only be picked up by the closest receiver. 

The red LEDs in the kit are low bright as super bright LEDs are too bright for the plastic model.
The 4 dummy red lens are removed and the 3mm LEDs fit very neatly.
The shorter cathode leads are at the bottom and one anode lead is bent over to touch the other anode lead.
Both the leads are cut very short and soldered very quickly to prevent them being damaged.
The two cathode leads are also cut very short.
0.2mm enamelled wire is included in the kit and the end is tinned by firstly scraping off the enamel or using the iron to burn off the enamel.
Tin one cathode lead very quickly and solder the wire to it.
Do the same with the other cathode lead.
The third enamel wire is soldered to the middle of the anodes and the three enamel wires are then taken down the back of the pole and taped with sticky-tap to hide them from view.
These three wires can be extended to the project with hook-up wire.
The other crossing light is wired exactly the same and the 3 enamel wires are are joined to the hook-up wire to make a parallel connecting with the first crossing light. 
The following two diagrams will help you with the wiring:

Easy-to-understand circuit

Connecting the sensors to the PC board

The bottom 2 wires of the flat ribbon cross over.

Prepare the ends with tinned copper wire before fitting to terminal blocks

The bottom 2 wires of the flat ribbon cross over.


Note: wires 4 and 5 are crossed-over
The kit contains black sleeve. Cut 5mm and glue over the
LED to prevent the signal spreading.

Here is the normal price:

Two Bachmann HO crossing signals are included in the kit



Wiring the 3mm LEDs

The kit contains 2 boom gates because the Crossing Signals from Bachmann comes in a pair with 2 Boom Gates.
You will be able to use the Boom Gates at the same crossing as the Signals by using Talking Electronics Boom Gates project.  

All the components are included in the kit and everything is identified on the board.  The terminal blocks make it easy to connect all the leads after the board has been screwed to the layout.
Solder a short length 0.5mm tinned copper wire to the ends of the ribbon cable before fitting into the terminal blocks to hold the wire in place. 
It is best to use a DC supply but an AC supply up to 16v can be used as the single power diode will provide half-wave rectification and the regulator will just manage to deliver a smooth 5v at 50mA load.

$26.50 plus $6.50 post
Order a kit:  Crossing Sound MkII

2 - 220R
2 - 330R
1 - 1k5
5 - 2k2
1 - 2k7
1 - 22k

1 - 1k mini trim pot (some PCB's will have
    a pot to adjust the LED brightness)

1 - 100n monoblock
1 - 10u electrolytic
2 - 100u electrolytics

2 - 1N4148 signal diode
1 - 1N4004 power diode
4 - low bright 3mm red LEDs
2 - IR LEDs (transmitters)
2 - V4838 38kHz receivers
5 - BC547 transistors
1 - 78L05  3-terminal regulator (100mA)
1 - PIC12F629 with "Xing"
1 - 8 pin IC socket
2 - component header pins for test points

2 - Sensor Connector strips (see text)

4 - 2-way terminal block
3 - 3-way terminal block

1 - metre 5-wire flat ribbon
2 - Bachmann Crossing Signals
2 - Bachmann Boom Gates (use in Boom
    Gates project)
2 - 10cm 0.6mm wire for boom push rod
1cm black sleeve to cover IR Tx LEDs.
3metre 0.2mm enamelled wire
      (for LEDs on Crossing Signals)
20cm 0.5mm tinned copper wire (for ends
        of ribbon cable into terminal blocks
        to make the screw grip the wire)
1 - 8R mini speaker
20cm very fine solder

1 - Crossing Sound MkII PCB
2 - Sensor Connector PCB's

Talking Electronics has a number of pieces of TEST EQUIPMENT to help in the design and testing of projects.
Of course you can use a multimeter for most of the testing but some of the "tricky" faults need a special piece of equipment.
You may only need a LOGIC PROBE once a month, but the project you are designing will come to a stand-still if you can't locate a problem.
We designed all these projects because we needed them ourselves.
Add one of them to each order you place with Talking Electronics and eventually you will have the whole range.
Tests LEDs.
$1.50 plus $4.00 post

(buy a number of kits and pay
only one postage)
Only responds to resistance less than 50 ohms.
Ideal for digital projects as it tests connections very quickly.
$12.50 plus $6.50 post

(buy a number of kits and pay
only one postage)
LOGIC PROBE with PULSER - slimline
Detects HIGH and LOW signals on both TTL and CMOS circuits.
The piezo allows you to hear low frequency signals and the signal injector (Pulser) will over-ride clock signals to make a circuit operate at a reduced frequency.
$8.00 plus $6.50 post
20 different functions.
See article for the complete list of functions.
$18.00 plus $6.50 post
Tests transistors and shows the gain of the transistor.
Also has Signal Injector probe.
$21.50 plus $6.50 post
Simple Transistor and LED Tester - 3
Tests PNP and NPN transistors and LEDs.
Also teaches the amazing property of an air-cored coil in producing a high fly-back voltage.
$4.00 plus $3.00 postage.

(buy a number of kits and pay
only one postage)
Detects 240v AC mains hidden in walls etc.
Will also pick up RF signals from a keyboard to show you where Electromagnetic Radiation is coming from and giving you a headache.
$10.00 plus $4.50 post
Traces cables when the power is OFF.
Uses an FM radio to pickup beeps.
$10.00 plus $4.50 postage. 

(buy a number of kits and pay
only one postage)

Teaches how an op-amp works by using pots to control the voltages on the two inputs.
$24.50 plus $6.50 post
(comes with instructions)
Learn to program PIC chips.
Comes with a pre-programmed PIC12F629 chip with 3 routines.
$12.00 plus $6.50 post
model railway POINT MOTOR CONTROLLER and TESTER   CDU-Inline
The cheapest CDU project you can get.
$8.50 plus $6.50 post