The 555 timers I use don't always generate pulses

  • #1
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Main Question or Discussion Point

I have 3 555 timers. They don't always produce pulse. Sometimes
They do. Sometimes they don't. Why don't they always produce pulses? I use electrolytic capacitors.
There is nothing connected to the 5th pin.
 

Answers and Replies

  • #2
davenn
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I have 3 555 timers. They don't always produce pulse. Sometimes
They do. Sometimes they don't. Why don't they always produce pulses? I use electrolytic capacitors.
There is nothing connected to the 5th pin.

hi there

well, you have given us very little to go on to try and help you
A circuit diagram of YOUR circuit would be helpful
As would a well lit and focused photo or two of your construction

With both of those things we may be able to see an error in your circuit and/or an error in your construction

Give us information of how many pulses per second or what ever that you were expecting to get
and what is the 555 circuit supposed to be driving ( what other circuit)

There is nothing connected to the 5th pin.
That's probably a main part of the problem as pin 5 is pretty much always used.
Unless it has a specific control voltage on it from another circuit, then it is ALWAYS grounded ( to 0V rail)
via 0.01uF ceramic, mylar etc capacitor


Dave
 
  • #3
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So I should ground the 5th pin with a capacitor?
 
  • #4
davenn
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  • #5
Baluncore
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Check also that the Not_Reset pin 4, is connected to Vcc which also goes to pin 8.
 
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  • #6
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Why is pin 5 connected to a capacitor?
 
  • #7
Baluncore
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Inside the 555 there are three identical resistors in series between the Vcc and the ground terminal. That voltage divider provides 1/3 Vcc and 2/3 Vcc reference voltages to the internal comparators. Pin 5 is connected to the upper divider voltage. A capacitor to ground removes power supply noise from the potential divider and comparator inputs, so the timing is more accurate with less jitter.
 
  • #8
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I tried using a 0.1μf polyester capacitor
Connecting pin 5 to ground. That didn't work. I tried using a different 555 timer. That didn't
Work. Could there be something wrong with the capacitor? The circuit is in astable mode.
 
  • #9
Baluncore
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The problem is that you have not given us your circuit diagram.
Post a link or drag and drop an image onto your next post.
 
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  • #10
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This doesn't really answer your question, but...
The 555 timer is one of the oldest ICs available. As such there are lots and lots of better IC timers available at low cost. Honestly, I can't imagine why anyone would still use a 555. For example, consider the 7555 which is functionally nearly identical but has much improved performance, these can often be directly substituted in a circuit.
For a modern design, you could look into TimerBlox ICs from Analog devices or other similar ICs.
 
  • #11
davenn
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I tried using a 0.1μf polyester capacitor
Connecting pin 5 to ground. That didn't work. I tried using a different 555 timer. That didn't
Work. Could there be something wrong with the capacitor? The circuit is in astable mode.
That may be because you still have other issues with your circuit/construction

I have asked for YOUR circuit diag and a photo or two of your construction way back in post #2

you still haven't provided these .... it's really difficult to help you better without this info ....
otherwise we are all just wasting out time guessing at what the problems may be

Dave
 
  • #13
dlgoff
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I use the circuit diagram from this site.
What did you use for a power supply? And at what voltage?
 
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  • #14
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I have two breadboards, a grey one
And a white one. I tried the white one
And the circuit started producing pulses. Sorry. I didn't try that until 1
Hour and 47 minutes ago. Do you have
Any idea what is wrong with the grey
Breadboard? and I have white breadboard, nothing wrong with white
Breadboard.
 
  • #15
gneill
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"Grey" and "white: don't adequately describe the breadboards. For all we know they may be wired very differently. You need to provide details about their configurations, manufacturer, model number...
 
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  • #16
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I will do some research.
 
  • #17
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I got the grey breadboard from a seller
On ebay. I am unable to provide more
Details. I bought the white breadboard
From mouser electronics. Diligent, is
The manufacturer of the white breadboard. Both breadboards look
Identical, except for the different colors. They have the same number of points. Both have a positive terminal
And negative terminal on each side.
 
  • #18
Averagesupernova
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Honestly, I can't imagine why anyone would still use a 555.
For the same reason I don't use a micrometer when framing a house. Sometimes good enough is good enough.
 
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  • #19
davenn
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I have two breadboards, a grey one
And a white one. I tried the white one
And the circuit started producing pulses. Sorry. I didn't try that until 1
Hour and 47 minutes ago. Do you have
Any idea what is wrong with the grey
Breadboard? and I have white breadboard, nothing wrong with white
Breadboard.

You STILL haven't provided photos.... PLEASE do so you are making people guess
and it again is still just wasting time
If you really want help, you need to help us help you
 
  • #20
davenn
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The 555 timer is one of the oldest ICs available. As such there are lots and lots of better IC timers available at low cost. Honestly, I can't imagine why anyone would still use a 555.
So ??

because they work and are easy to use
 
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  • #21
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So ??

because they work and are easy to use
Not for the OP :cool:

Cheers
 
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  • #22
davenn
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Not for the OP :cool:

Cheers

Probably only because he has a wiring error

hence my continued insistence for photos !!
 
  • #23
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Here are the photos of my breadboard.
 
  • #24
berkeman
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Those are photos of blank breadboards, before any circuitry that you added onto them. Can you please post clear pictures of the non-working circuit? Thanks.
 
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