Recently I needed a square wave to mess around with some filters, however I didn’t have one. So I decided to build one based on the ever so popular 555 timer chip! My inspiration is from the Australia electronics magazine Talking Electronics, the project is in Issue 3. After a bit of research about the 555 and how it works, I created the final circuit ready to be used. The circuit is below (I still don’t have a proper circuit schematic drawer program, so please excuse the illustration):
At first I built the circuit on the breadboard and it worked perfectly, it was producing the frequencies that I wanted (tested by both an LED and the oscilloscope). The LED (illustrated as a lamp in the schematic) is optional, some may find it annoying because it flashes at low frequencies (At 1 and 10Hz), but I still haven’t made up my mind if I like it or not. Now below is an image of how it turned out on the breadboard. To the left of the image you can see the way I was testing different capacitors to see how different values worked out.
After testing everything and checking that it is fully functional I began to assemble the circuit onto a prototype board.
As you can see in the image above I used an 8 Pin DIP socket. I recommend if anybody builts this they use the socket. It protects the IC from heat when you solder. So basically you just put the socket and solder it onto the board and then just slide the IC into the socket. Simple and your IC isn’t damaged! Below are the final results of the build.
Look at the field of depth on those images! As you can see I have a little input slot for the input voltage which makes it versatile for different voltages (4.5v to 16v). Also I have soldered the four capacitors onto the board itself, combining the ground and then bringing the positive wire from them out onto the top side of the board so that I can attach the little alligator lead ( from pin 2, which is connected to pin 6 via the jumper) to be able to select different frequencies quickly.
I am not sure if that is how you are supposed to solder onto the prototype board, but either way it works! After a few more test on the new soldered version I realised that for some reason my tantalum capacitor was giving me around 850 Hz instead of 1 KHz, but everything else worked fantastic! A few images on the scope:
This is a good project if you are a beginner wanting to start with IC’s. I learnt so much while building this circuit and through researching the 555 not to mention that you also get a fully operational square wave generator one you are done. I highly recommend this!
This is a good resource for messing around with the values of the 555 timer: 555 Calculator
Purchase the IC on Amazon (best value for money options):
Here is a little overview on how the 555 works from Talking Electronics ( Australian electronics magazine ) it is a pdf of issue 6, skip to page 36 of the pdf for the 555 timer tutorial Talking Electronics Issue 6
And of course the data sheet from National Semiconductor Datasheet
Also here is the pinout for anyone who needs it.