Pages 63 to 85

                                                              Index
                                                   Pages:    1 to 21
                                                   Pages:    22 to 41
                                                   Pages:    42 to 62





The pages can be printed and collated into a book for easy reference.

More circuits and projects can be found on TALKING ELECTRONICS website:
http://www.talkingelectronics.com


Colin Mitchell
talking@tpg.com.au

Tel: 0417 329 788

 

Page 63

40106 OR 74C14 HEX Schmitt Trigger IC

Here are some of the things you can do with the gates in the 40106 Hex Schmitt Trigger chip:

INVERTING
If the output is required to be the opposite of the circuit above, an inverter is added:

If a diode is added across the input resistor, the capacitor "C" will be discharged when the input goes low, so the "Delay Time" will be instantly available when the input goes HIGH:

The following circuit produces a PULSE (a LOW pulse) when the input goes HIGH:

Page 64

To invert the output, add an inverter:

To produce a pulse after a delay, the following circuit can be used:

The following circuit produces a tone during the HIGH period. When the output of the second inverter is HIGH, it places a high on the input of the third inverter, via the diode. This is called "jamming" the oscillator and prevents the oscillator from operating. When the second inverter goes LOW, the oscillator will operate.

The oscillator above can be set to produce a 100Hz tone and this can activate a 2kHz oscillator to produce a 2-tone output. A "jamming diode" is needed between the third and fourth gates to allow the high-frequency oscillator to operate when the output of the low-frequency oscillator is HIGH.
 

The output can be buffered with a transistor:

Page 65
Extending the action of a push button
The action of a push button can be extended by adding the following circuit:

To produce a pulse of constant length, (no matter how long the button is pressed), the following circuit is needed:

GATING
Gating is the action of preventing or allowing a signal to pass though a circuit.
In the following circuit, buttons "A" and "B" are gated to allow the oscillator to produce an output.
The first two inverters form an "OR-gate." When the output of the gate is HIGH it allows the oscillator to operate.

The second diode is called the gating diode. When the output of the second inverter is LOW, the capacitor is prevented from charging as the diode will not allow it to charge higher than 0.7v, and thus the oscillator does not operate.
When the output of the second inverter is HIGH, the capacitor is allowed to charge and discharge and thus oscillator will produce an output. If the push buttons can be placed together, the circuit can be simplified to:

PULSER
The 74c14 can be used to produce a 3mS pulses every second. The circuit is adjustable to a wide range of requirements.
                                     
 

Page 66

2 MINUTE TIMER
Some of the features we have discussed have been incorporated into the following circuit. The relay is energized for a short time, 2 minutes after the push-button is pressed. The push-button produces a brief LOW on pin 1, no matter how long it is pushed and this produces a pulse of constant length via the three components between pin 2 and 3.
This pulse is long enough to fully discharge the 100u timing electrolytic on pin 5.
The 100k and electrolytic between pins 6 and 9 are designed to produce a brief pulse to energize the relay.

TRIGGER TIMER

The next design interfaces a "Normally Open" and "Normally Closed" switch to a delay circuit.
The feedback diode from the output prevents the inputs re-triggering the timer (during the delay period) so that a device such as a motor, globe or voice chip can be activated for a set period of time.
 

ALARM
In the following circuit, the gates are used to detect the touch of a door knob and produce an output that goes HIGH for approx 1 minute.

The output of the above circuit can be taken to an alarm. Open the reed switch contacts and connect the reed switch to the output of the Door-knob alarm.    

Page 67

LM 386

               300mW amplifier using LM 386

 
            300mW amplifier using LM 386

Page 68

    

Page 69
 

 A 330k SM resistor

Surface Mount Resistors
All SM resistors conform to a 3-digit or 4-digit code. But there are a number of codes, according to the tolerance of the resistor. It's getting very complicated.
Here is a basic 3-digit SM resistor:
 

The first two digits represent the two digits in the answer. The third digit represents the number of zero's you must place after the two digits. The answer will be OHMS. For example: 334 is written 33 0 000. This is written 330,000 ohms. The comma can be replaced by the letter "k". The final answer is: 330k.
222 = 22 00 = 2,200 = 2k2 
473 = 47 000  = 47,000 = 47k
105 = 10 00000 = 1,000,000 = 1M = one million ohms
There is one trick you have to remember. Resistances less than 100 ohms are written: 100, 220, 470. These are 10 and NO zero's = 10 ohms = 10R 
or 22 and no zero's = 22R  or 47 and no zero's = 47R.  Sometimes the resistor is marked: 10, 22 and 47 to prevent a mistake.
Remember:
R = ohms     k = kilo ohms = 1,000 ohms     M = Meg = 1,000,000 ohms
The 3 letters (R, k and M) are put in place of the decimal point. This way you cannot make a mistake when reading a value of resistance.

THE COMPLETE RANGE OF SM RESISTOR MARKINGS:

Page 70
The complete range of SM resistor markings for 4-digit code: 

0000 is a value on a surface-mount resistor. It is a zero-ohm LINK!
Resistances less than 10 ohms have  'R' to indicate the position of the decimal point.  Here are some examples:

A new coding system has appeared on 1% types. This is known as the EIA-96 marking method. It consists of a three-character code. The first two digits signify the 3 significant digits of the resistor value, using the lookup table below. The third character - a letter - signifies the multiplier.

Page 71

The multiplier letters are as follows:

22A is a 165 ohm resistor, 68C is a 49900 ohm (49k9) and 43E a 2740000 (2M74). This marking scheme applies to 1% resistors only.

A similar arrangement can be used for 2% and 5% tolerance types. The multiplier letters are identical to 1% ones, but occur before the number code and the following code is used:

With this arrangement, C31 is 5%, 18000 ohm (18k), and D18 is 510000 ohms (510k) 2% tolerance.
Always check with an ohm-meter (a multimeter) to make sure.

Chip resistors come in the following styles and ratings:
 Style: 0402, 0603, 0805, 1206, 1210, 2010, 2512, 3616, 4022
 Power Rating: 0402(1/16W), 0603(1/10W), 0805(1/8W), 1206(1/4W), 1210(1/3W), 2010(3/4W), 2512(1W), 3616(2W), 4022(3W)
 Tolerance: 0.1%, 0.5%, 1%, 5%
 Temperature Coefficient: 25ppm 50ppm 100ppm

CAPACITOR DATA

Page 74

Page 75

STEAM SIMULATOR

A realistic steam sound can be generated with a 4-transistor directly-coupled amplifier connected to a small speaker. The “white noise” is generated by the breakdown across the junction of a transistor and it is activated by a switch made up of contacts touching the wheel of one of the carriages. As the train speeds up and slows down, the sound corresponds to the movement.   See Talking Electronics website for the full project.

Page 76

27MHz LINKS

.

Here is the circuit from a 27MHz remote control car. It is a simple single-channel link that activates the car in the forward direction when no carrier is being received, and the motor reverses when a carrier is detected. See Talking Electronics website for more details – 27MHz Links.  

Page 77

This is a single channel receiver, similar to the circuit above.
It can be modified to turn on a “latch” a relay. This means the relay can be turned on remotely but
it cannot be turned off.  The second circuit shows the modification to turn the relay ON with a short
tone and OFF with a long tone.

The relay can be turned on but not turned off

The relay can be turned on with a short
tone and turned off with a long tone

SOLAR CHARGER

This solar charger can be used to charge a 12v battery from any number of solar cells. The circuit automatically adjusts for any input voltage and any output voltage.   See Talking Electronics website for the full project.

Page 78
 

ARC WELDER

The Arc Welder project is one of many projects for model railroads - see Talking Electronics
website for the list of projects.

Page 79

Field strength Meter MkII
.

A field strength meter is a very handy piece of test equipment to determine the output of a transmitter.
Talking Electronics website describes a number of Test Equipment projects to help with developing your projects.

Page 80

INFINITY BUG

THE SURFACE-MOUNT COMPONENTS OF THE INFINITY BUG

The Infinity Bug sits on a remote phone and when the handset is returned to the rest position, the caller whistles down the line and a very sensitive microphone connected to the infinity bug is activated and any audio within 5 metres is detected.   

Page 81
 

FM BUG

                       FM BUG CIRCUIT

 

     FM TRANSMITTER   - 88MHz – 108MHz

The FM Bug is one of many FM transmitters designed by Talking Electronics, to show how
far a simple transmitter can reach on a few milliwatts. It is most fascinating to see your
transmitter being detected at 400metres.
 

3-Transistor Amplifier
 

                          The surface-mount 3-Transistor amplifier

HEARING AID

Page 83

THE AMMETER

(0 - 1uA uses a 1uA movement)

 

THE MICROPHONE
Basically there are two different types. One PRODUCES a voltage and the other REQUIRES a voltage for its operation. 
This means you need to supply energy to the second type and this is very important when you are designing a battery-operated circuit and need to have a very low quiescent current. 
Here is a list of different types of microphones and their advantages: 

Page 84

If a microphone produces about 20mV under normal conditions, you will need a single stage of amplification. If the microphone produces only 1mV under normal conditions, you will need two stages of amplification.
The circuits below show the first stage of amplification and the way to connect the microphone to the amplifier.

      

Connecting an electret
microphone.  


  

The 100n capacitor separates the voltage needed by the microphone (about 1v) from the 0.6v base voltage. A good electret microphone can hear a pin drop at 2 metres. A poor quality electret mic produces crackles in the background like bacon and eggs frying.

The internal construction of an electret microphone
Air enters the electret mic via the top holes and moves the thin mylar sheet. This changes the distribution of the charges on the plastic and the changes is passes down the Gate lead to the FET. The FET amplifies the signal and the result is available on the Drain lead.  

     
                                                                   Connecting a Crystal  microphone

 
              
The crystal microphone has an almost infinite impedance - that's why it can be connected directly to the base of the transistor. 
The magnetic microphone has a very low internal resistance and needs a capacitor to separate it from the base of the amplifying stage. If it is connected directly, it will reduce the base voltage to below 0.7v and the transistor will not operate.

PIEZO DIAPHRAGM
You can also use a piezo diaphragm as a microphone. It produces a very “tinny” sound but it is quite sensitive. Some diaphragms are more sensitive than others, but the sound quality is always terrible.

Page 85

 MICROCONTROLLERS

Microcontrollers are the way of the future. Most of the basic theory you will learn for the individual components in this ebook will become very handy when you need to design a circuit.
As a circuit becomes more and more complex, you have a decision to make. Do you want to use lots of individual components or consider using a microcontroller?
Talking Electronics website has a number of projects using individual components and this is the only way the project can be designed. But when it comes to “timing” and requiring an output to produce a HIGH for a particular length of time after an action has taken place, the circuit may require lots of components.

This is where the brilliance of a microcontroller comes in.

It can be programmed to produce and output after a sequence of events and the circuit looks “magic.”  Just one component does all the work and a few other components interface the inputs and output to the chip.

The second special thing about micros is the program.
This has been produced by YOU and it can be protected from “prying eyes” by a feature known as “code protection.”
This gives you exclusive rights to reproduce the project and all your hard work can be rewarded by volume sales.

This is the future. 

Talking Electronics website has a number of very simple projects using microcontrollers and these chips all belong to the PIC family of micros.

These chips are very easy to program as they only have 33 - 35 instructions and they can perform amazing things.
See the Talking Electronics website for project using these micros.  
The three micros covered on the website are:   PIC12F629, PIC16F84 and PIC16F628.  The MCV08A is a Chinese version of the PIC12F629 and has some extra features and some of the features in the PIC12F629 are not present. But the cost is considerably lower than the PIC12F629. The Chinese get special deals all the time.

Page 86

 

HERE IS A PROJECT
USING A MICROCONTROLLER:

SIMON

                         SIMON PROJECT USING PIC16F628

SIMON is the simple game where you repeat a sequence of flashing coloured lights.
All the “workings” of the project are contained in the program (in the PIC16F628
microcontroller) and the program is provided on Talking Electronics website. 
See Simon project for more details.
 

This completes Data Book 1.   Look out for more e-books on Talking Electronics website:

http://www.talkingelectronics.com

Sept 2008    Nothing is  copyright.  You can copy anything.       Colin Mitchell

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