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Topic: 555 timer - failed at the first hurdle [FIXED] (Read 7223 times) previous topic - next topic

acboother

5.27 v on source 3.9v across pin1-8

sticking the the 2k on the output does this to the scope



and



and just to make the point about the 9v here is the scope output




larryd

If you have the parts try this combination.
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acboother

capacitor 1 say 104

swapped out with another saying

4.7uF



sorry can't closer and focus

acboother

By the way, nobody has commented on the fact that the 555 gets very hot

runaway_pancake

Pin 4 should be = supply volts
Pin 8 should be = supply volts
or there's a problem.

You should jumper the Gnd bus on the one side over to the one on the other side.
Then ground your caps on that rail/bus instead of running the jumper leads as you are.

If this is a CMOS 555 (7555 or LMC555) then it should run from a 9V battery OK.
If it's an LM555, a bipolar device, then it will suck (big transients on transitions) and will get hot depending on the load.

Placate the bypass crowd by placing a 0.1uF, from +V to Gnd on your power bus.
"Who is like unto the beast? who is able to make war with him?"
When all else fails, check your wiring!

larryd

Quote
555 gets very hot


Well we have to ensure things are wired correctly and the correct components are used before we say "try another 555".
Otherwise the new chip will get very hot.

Can you try the circuit I showed you?
Quote
"If you have the parts try this combination."
No technical PMs.
If you are asked a question, please respond with an answer.
If you are asked for more information, please supply it.
If you need clarification, ask for help.

acboother

I'm going to 'rebuild' with single core and remove the jumpers. Remove/reduce the mechanical issues and perhaps something will show up in the tidy up.

Found other forums where people have mentioned very hot 555s. Seems like the most likely outcome is it is fryed but I'm still going to keep at it.


acboother

Larry, I'll check for components and compare the circuit you have with what I thought I was doing.

acboother

Here it is cleaned up



Exactly the same result. Didn't have those components but I feel that these should be okay.

Have set the variable resistors and checked with a multimeter. (Now using the centre pins)
Have checked the connections.

Options left are that I have gone wiring blind and the circuit I have built is not what the circuit diagram says and/or I have fried the chip in my efforts.


AmbiLobe

Maybe...
The protoboard is 18 months old and it has bent conductors from old circuits with 18 gauge wires.
The pot has wires that are very thin.
The ceramic capacitor has wires that are very thin and it is using protoboard holes that were damaged in 2011.

Pull the components and photograph a side by side image of the thinest wire next to your fattest wire.
Maybe we will see an 18 gauge jumper next to a 28 gauge pot wire.

acboother

AmbiLobe how did you know the board was 18months old?

By the way it is only a couple of months old and barely used as I use the wider 6 lane ones by preference...

I don't think there are connection problems I suspect this is just a shot in the dark

larryd

The 2 wires going to Breadboard #21(which go to 555 pin 3) are used for the scope?

Battery is 9 volts?

Everything looks OK so there is no reason why the timer should get hot.
I would try a new timer.
As a side issue try to use the CMOS version rather than the TTL.
The TTL version produces huge glitches on the power line.
No technical PMs.
If you are asked a question, please respond with an answer.
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acboother

Okay, I have enough confidence to say the chip is 'NO LONGER'... RIP 555

So it was no good from the start or I fried it...

I poked about for another 555 and found one on some old board I think was used for a cat/bird scarer. I unsoldered it and the pins were too short so I made this nasty looking thing and plugged it in. Looks like some sort of microbot :)

And wahey it works. So the old chip is is dead and destined for some art piece.

Thanks everybody for the interest, help and time you've spent with me... anytime you're around just drop in for a coffee.

larryd

If you can burn out another 555 you can give your wife earrings.

Things ruined varies directly with experience.

No technical PMs.
If you are asked a question, please respond with an answer.
If you are asked for more information, please supply it.
If you need clarification, ask for help.

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