Introduction: Test Tools: a Fairly Simple 555 Tester. Corrected and Updated.
Here I will give a small circuit that will test whether the 555 timer you just tried in another circuit (and it either heated up or didn't work at all) works or not.
Have you ever wondered if it was your circuit, or whether might have fried your 555? Well here is a way to test the little chip quickly and easily.
Step 1: Gathering the Parts
Parts and cautions.
Depending on your hearing or what you find best as far as the sound produced by the output, you will need to figure out what resistors and capacitor you wish to use for the timer section of the circuit.
This is an Astable multivibrator circuit. When the switch is closed, the output is a square wave at the frequency determined by C1, R1 and R2.
The needed calculations to find the values are as follows:
f = 1.44 / (R1 + 2R2) X C1
The period (time - t) of the circuit is found with: t = 1/f = 0.69(R1 +2R2) X C1
The high and low times of each pulse can be calculated also with:
High time = 0.69(R1 + R2) X C1
Low time = 0.69(R2 X C1)
Take note that it is practical to keep the values of R2 between 1K and 1M. To keep the duty cycle around 50%, use R1 = 1K.
So, once you have the frequency you wish to generate, and have figured out what R2 and C1 are to be, and you have gather those parts the only things you need yet are
One PC board
One 8 pin IC socket
One 555 timer
One 47uF capacitor (C1)
One 10 nF ceramic capacitor
One 10k to 100k Potentiometer
a soldering iron (or prototype board)
and your goggles.
Step 2: Putting It All Together
As I said, it is pretty straight forward. If you get one of the PC boards made to put the socket in the center column of the board, and has traces that go from the initial solder point outwards and fan out a bit for easier soldering.
Solder in the parts and wires to connect the various parts as shown in the schematic.
Remember to solder pin 2 to pin 6. Solder the decoupling capacitor, C3 (not shown) between Power in and ground if you are not using a battery. If you wish to use the optional frequency adjustment, add it in series with R1. Power goes to pin 4 (5-15 v DC). R2 is the connection from pin 6 to pin 7. Since we are not going to use pin 5, the control voltage, we should decouple it to ground with a 10 nF capactor (C2 :-) .
Overview of the 555. Pin 1= ground
Pin 5=control voltage
Pin 8=3-15 vdc
Step 3: Solder It, Then Box It
Once you have all the parts soldered in, and have tested the circuit. You can add the Pot. inline ie in series with, R1 or R2 (I used R1 so I could adjust the duty cycle as I wished).
Find a decent box to put it in and remember to allow for a place to get to the socket so you can use this as a tester.
The entry point for the timer was altered and made so much more neater. I used an old gold colored aluminum card blank and cut the hole after measuring it for locationi.