# 555 timer circuit help?

Discussion in 'General Electronics Discussion' started by Dasitmane, Feb 26, 2016.

1. ### Dasitmane

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Feb 26, 2016
I want to make this basic circuit but with a pot to get an adjustable frequency

How can I modify this to use a pot??

I tried what I thought would work, but it didn't function from what I could tell.

2. ### Gryd3

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Jun 25, 2014
Awesome. Good to see someone trying to pick something up like this.
Show us a circuit diagram or sketch of what you tried, let's point you in the right direction.

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Jan 28, 2013
4. ### Dasitmane

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Feb 26, 2016
Last edited: Feb 27, 2016
5. ### cjdelphi

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Oct 26, 2011
The heart of it so to speak, is the timing capacitor/potentiometer..

What do you have in mind for it? (The 555 is the swiss army knife of the electronic world)

6. ### Kiwi

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Jan 28, 2013
This site has a great little program called "Electronics Assistant V4.31".
It has heaps of calculators, eg 555 timer, resistors in parallel or series, LED series resistor, etc.
And the best part is that it is FREE!
http://www.electronics2000.co.uk/

7. ### cjdelphi

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Oct 26, 2011

It's very comprehensive, it's saved my butt a few times

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8. ### Dasitmane

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Feb 26, 2016
Ok, so I got all my parts in the mail for this, I got a few extras of each cause why not, and my pots are 200 instead of 250 k, but I figure that wont matter to much. But, in all honesty, I'm having trouble understanding what to hook where in respect to the 555 times since the pic is quite a bit blurry. Whats the best way to figure out how to lay down whats in the schematic on a breadboard?

This is the circuit that I am using by the way.
http://www.electronicecircuits.com/electronic-circuits/555-variable-frequency-square-wave-generator

EDIT: So I actually changed my plan and just decided to use this more simple circuit.

If it is even applicable to what I am trying to accomplish. So I wired it up, and here are some of the pics of what I have so far, I'm sure there are errors so please let me know.

The power is the line going to 8. And the ground is not in in these photos.

Basically is all I'm trying to do is produce a lower range frequency(square or sine), if they still made radio coils I would probably just use that and a capacitor lol.

Last edited: Mar 14, 2016
9. ### AnalogKid

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Jun 10, 2015
What is the value of R1 (from pin 8 to pin 7)?
What is the value of the timing capacitor?

What are you using to look at the output? If you want an LED to blink slowly enough to be visible, the capacitor probably will have to be larger.

ak

10. ### cjdelphi

1,096
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Oct 26, 2011
I see several mistakes....

I see only 1 resistor, you're missing 1, you also have a low ceramic value prob under 1uf, no problem though, with large enough resistance, also you made the curcuit difficult to build, use the rails at the top and bottom (if you have hookup wire)

Lastly although not an issue, you appear to be using 1/2watt resistors for a 1/4watt job

11. ### AnalogKid

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Jun 10, 2015
The other resistor is the two black wires going off to the pot in the middle pix.

ak

1,096
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Oct 26, 2011
Ahh.. ok

13. ### Bluejets

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Oct 5, 2014
Think you need to look a little closer at the operation of the 555 and what resistor and capacitor values values are recommended as minimum.
Talking Electronics have a good free online book on 555's and many circuits available with circuit explanations.
R1 looks like 20R to me but could be wrong.
Wiring twisted into a pot terminal like you have will cause intermittent operation.
A pot used in this way could at some time be turned down to zero, not a good idea.
If you must use a pot, use a minimum value resistor in series to avoid the problem.

14. ### AnalogKid

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Jun 10, 2015
My guess is that he order a 20 thinking everyone always knows it means 20K.

ak