Print PDF
Favorite
Email
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.
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.
Remove these ads by
Signing UpStep 1Gathering 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
some wire
a soldering iron (or prototype board)
and your goggles.
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
some wire
a soldering iron (or prototype board)
and your goggles.
| « Previous Step | Download PDFView All Steps | Next Step » |
pin one-ground from power source
pin two- trigger,ahhhh put a current through it and it starts the sucker???
pin 3-output, too the LED/Speaker/Nuclear Detonator
pin 4- reset, kinda like the trigger connect it to the power source with a switch?
pin 5-offset, no idea
pin 6&7-discharge and threshold, connect the capacitor/resistor combo to these pins(positive of electrolytic caps going to which one?)
pin 8- 3-18v from power supply
If you could explain the ones that I got wrong and had questions on great, if you can teach me more great, if you can direct me to a super good guide somewhere (once again) GREAT.
I feel so long winded....:D
Kind of, the trigger need only be a pulse.
pin 5-offset, no idea
Also labeled control voltage or Bypass.
6 is "threshold" and 7 is discharge
Now, a little bit about the chip: 555s are configured as a multivibrator by adding a few components to the pins. This is a circuit that oscillates from one state to another over time, in this case, creating a square wave. There are two basic forms of timers, both being multivibrators: monostable and astable.
The monostable is also called a one-shot. A single trigger creates a change in the output (either bringing it down to zero or turning it on). The astable swings back and forth, from one state to the other and back again.
Instead of going into long explanations, maybe this will be of some assistance.....here is a site that has a bunch of schematics and explanations on it, AND has a calculator to boot :-)
I am willing to help in any way you might need, but a few simple reads should get you up to speed.
There is a nice tutorial at this link here that should answer any questions you have for now. If not, myself or someone else here can help .
PS: if you wish to use an even LOWER powered chip that is otherwise the same as the 555, you can get the CMOS version, namely the 7555 as it is capable to operate from 2.7v to 18v. At 5v, the 7555 will consume about 900 microwatts, making it ideally suitable for battery operated circuits. The internal schematic of the 7555 is similar to the standard 555 but with current-spiking filtering, lower output drive capability, higher nodal impedances, and better noise reduction system. The pinout is the same.
And Alex is correct about the Potentiometer.
Alex is also correct concerning the interpretation. In the case of my crude tester, it only verifies that does function and not so much whether it is functioning perfectly.
With or without the potentiometer, there will be a sound / i.e. a kind of whine that comes from the speaker if the 555 can oscillate. A fried one (damaged by being overheated in the soldering process or a shorted joint or whatever may occur) will not oscillate....and no sound will come from the speaker.