The 555 Riddle: My 555 wont work, I've tried everything!

Alen Glenie

Joined Jun 22, 2016
2
I have had bad breadboards. use a different breadboard? Some times higher wattage components have larger leads (that plug into breadboard) and these can stretch/distort the conductors in the breadboard. Then you have an unreliable connection.. hence the circuit works intermittently or not at all.
You could just move the project over a few lines and it will work. From all the previous comments, and everything you have tried, this seems the most likely scenario.
 

OBW0549

Joined Mar 2, 2015
3,566
The classic 555 astable multivibrator circuit is about as foolproof as a circuit can possibly get; it's been built by tens of thousands of people in the nearly half-century since the 555 was first introduced, and when built EXACTLY as tracecom described in post #4, WILL work correctly barring a defective component, wiring error or flakey power supply. Make sure you include capacitors C2 and C3 shown on his diagram. C3 is especially important, as the 555 needs a well-bypassed power supply to function correctly due to its high shoot-through current when the output changes state.
 

Thread Starter

Barrythecableguy

Joined Jun 14, 2016
48
Thank You so much after weeks of frustration I have finally built an astable 555 setup, I have included a picture below. You are absolutely right reading schematics is definitely a weakness of mine and I am trying to get better,but if you know of any literature that could help please forward it to me. Also I believe I owe you $10 dollars, if you would like to collect then send me your email address and ill send you a paypal payment.

Thanks again Barry

upload_2016-6-27_15-20-55.pngu
 

papops

Joined Mar 21, 2016
5
Barry,

This may sound silly but I'd buy a handful of 555's and try another chip in place of the one you've been using. This circuit is very, very simple and it's hard to make a mistake in wiring, therefore I'd be looking for faulty components.

Walt
 

Thread Starter

Barrythecableguy

Joined Jun 14, 2016
48
Barry,

This may sound silly but I'd buy a handful of 555's and try another chip in place of the one you've been using. This circuit is very, very simple and it's hard to make a mistake in wiring, therefore I'd be looking for faulty components.
Ok thanks, would this circuit work with a 556 ?

Barry

Mod edit: put response outside of QUOTE tags
 
Last edited by a moderator:

EM Fields

Joined Jun 8, 2016
583
I am going to spend the next couple of days doing research on this, I dare not dismantle the circuit in case I cannot get it to work again

Barry
If you're afraid that it could become the lost chord, generate a schematic, replicate the circuit on a new breadboard, and do your experimenting there, knowing that, no matter what, you have recourse to the uncorrupted source.
 

JohnInTX

Joined Jun 26, 2012
4,787
If you're afraid that it could become the lost chord, generate a schematic, replicate the circuit on a new breadboard, and do your experimenting there, knowing that, no matter what, you have recourse to the uncorrupted source.
Good advice. You could probably replicate it on the other half of the breadboard, too, and have an A-B test thing going. But, eventually, you'll have to overcome your doubts and just get onto it. There is no one here of any stature (or anywhere else) that hasn't been where you are. 'When it doubt, pull it out'. Trial and error is an acceptable method when getting started.
 

tracecom

Joined Apr 16, 2010
3,944
If you're afraid that it could become the lost chord, generate a schematic, replicate the circuit on a new breadboard, and do your experimenting there, knowing that, no matter what, you have recourse to the uncorrupted source.
The schematic is in post 8 and a photo of a working breadboard is in post 20.
 

hp1729

Joined Nov 23, 2015
2,304
Thank You all for your kind help in resolving my previous capacitor issues, I now have a new challenge and I am completely stumped. This time it concerns the “555 IC” This thing is driving me mad, I’m trying to get it to run in “astable mode” in order to make an LED blink on and off, its mission impossible! I have viewed at least half a dozen circuits and built them exactly as instructed and the light will not blink on and off, it just comes on and then stays on! I have used the same value resistors, the same value capacitors, the same wires and the same power source as instructed. At first I thought it might have been the timer itself and so I used ten separate 555’s and the result was the same with every one of them, I’ve used different breadboards, I’ve used polarized wires and non polarized wires, I’ve tried different power sources, I even tried using a closing switch and even an LDR, nothing absolutely nothing will make my little LED blink on and off, everyone else’s blinks why won’t mine ? I am so desperate to fix this that as god is my witness I will give $10 to whoever helps me solve this! How can something so simple be so difficult, there must be someone out there who can get to the bottom of this apparent curse, someone step foreword!

The pictures are of my own attempts to build the circuit.

Bad 555?
Set is working, output is working but Threshold looks like it never gets recognized. Modify the design so you can manually pull Reset low (to test that). Manually pull Threshold high and see if that makes Discharge go low.

What should happen.
Trigger goes low (capacitor is discharged). Output goes high, Discharge is released from being held low and the capacitor starts charging. (Output works. Is the capacitor charging?)
When the capacitor reaches 2/3 of VCC the output goes low and Discharge goes low, discharging the capacitor. (Threshold is not being reached?)
When the capacitor discharges to 1/3 VCC the trigger point is hit and the show starts all over again.

You have changed the capacitor so it is not a bad capacitor. Bad chip?

Test the chip.
 
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