Digital Pulse Generator

Free Web Hosting Provider - Web Hosting - E-commerce - High Speed Internet - Free Web Page

Build This Easy Digital Pulse Generator Project to Drive Your TTL & CMOS Integrated Circuits

'Digital Electronics' is one of the fascinating fields in which you can enter! It is one of the prevailing 'Electronics' of our day and will be long into the future. The basic motor of all digital circuits are pulses. Digital clocks generates pulses that not only give us the time, but also drives the computers that work in our world.

To study and experiment with digital circuits, the more basic instrument in your laboratory would be the 'Pulse Generator'. This piece of equipment is essential to feed circuits like, for example, digital counters or dividing circuits and verify how they work.

I built this unit with only two integrated circuits; one is the famous NE 555 and the other is a current and voltage regulator...the LM 78L05. the NE 555 is a so-called 'monolithic circuit', packaged in an 8-pin mini DIP that you can buy also with other demoninations as XR-555, SE 555, MC 1455, MC 1555, LM 555...etc. These integrated circuits, as well as the LM 78L05, are cheap and quite easy to find in your local components' shop.

The rest of the components in the circuitry are readily available and non-critical...and they are:

You can lodge all the circuitry in a small cabinet. I made mine with an aluminum box that I reduced to the size of 10.5 cm's long.....6 cm's wide.....and 3.5 cm's high. If you wish working more comfortably, the dimensions of your cabinet may be incremented. The cabinet can be of a plastic material...if you prefer.

Semi-Conductors	Capacitors
NE 555 IC	.1uF/15v Mylar
LM 78L05 IC	100uF/15v Electrolytic
Diode LED	1uF/15v Mylar
...........................................	.1uF/15v Mylar or Ceramic
...........................................	.01uF/15v Mylar or Ceramic
Resistors	Other Components
1K 1/4 Watt	Two Switches SPDT Miniature
10K 1/4 Watt	Jack Socket 1/8 Inch Miniature
4.7K 1/2 Watt	Cabinet.....Plastic or Metal
100K Potentiometer	Nine Volt Battery

I mounted the circuit on a copper board in the 'Manhattan' style, but you can trace the drawing to make a printed circuit. Using the Manhattan technique saves you the complications of a printed circuit and working with ferric cloride.....a chemical that you always have to manage very carefully!

You can test the functioning of your generator by connecting its' output to a 4.7K resistor in series with a LED; respecting the polarities of the LED. When the frequency selector is placed to L (Low) position and the 100K potentiometer to minimum, you can see the LED flashing.

Another way of testing the unit it to connect its' output to a crystal earpiece. In any position of the controls, you will hear the pulses that arises to a musical note at the highest frequencies.

But the best way of testing the pulse generator, is when you have access to an oscilloscope; then you will realize not only that the generator works.....but you can now measure the frequencies of the pulses and the voltage at its' output. I measured an output voltage of 4.4 volts.....enough voltage to drive the TTL and CMOS integrated circuits of your digital projects.

Don't allow short circuits at the output of the generator!

A short circuit at its' output can overheat the integrated circuits and destroy one or both of them. Short circuits in electronics...analog or digital...must be avoided by all means....!

I wish you a happy time building the project and with it...plenty of success with all your 'digital circuits'!

I give thanks to my son-in-law, Juan Antonio Gomez Martin, who prepared the photos with his digital camera and very special thanks to my friend Patrick Cambre...who mounted this webpage so carefully with his professional know-how.