I've been trying to make an LED blink. My first approaches were without the 555 timer, and they were unsuccessful. I decided to make an Astable multivibrator circuit. I'm using an NE555, and I'm using the circuit on this video. For R1, I used a 680ohm resistor, and for R2 I've used 1k, 10k, 100k, 500k, 1M ohm resistors, and none of them have proven succesful. For my capacitor, I'm using a 100uF capacitor. I've tried 1uF and 1000uF aswell. Please help!

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    \$\begingroup\$ Most likely wire contact or wiring error. \$\endgroup\$ Dec 2, 2017 at 0:28
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    \$\begingroup\$ Can you add a schematic to your question, there is a built in tool? \$\endgroup\$
    – Tyler
    Dec 2, 2017 at 0:29
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    \$\begingroup\$ If you're working from a design that has been shown to work and yours isn't working you need to show us some info about your circuit. \$\endgroup\$
    – Kevin Reid
    Dec 2, 2017 at 0:29
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    \$\begingroup\$ Maybe the LED was burnt out from putting in backwards at >5V \$\endgroup\$ Dec 2, 2017 at 0:31
  • \$\begingroup\$ Are you sure you've got the capacitor connected with the correct polarity? \$\endgroup\$ Dec 2, 2017 at 4:53

1 Answer 1


First of all, try following a schematic rather than a youtube tutorial showing a breadboard. There is a good chance you may have wired something incorrectly.

A 555 timer in an astable configuration would look like this:


simulate this circuit – Schematic created using CircuitLab

Using this, you should be able to place your components on a breadboard, following the schematic closely. I assume you know the internal connections of a breadboard, but just in case, here is a diagram:

enter image description here

If you change the values of R1/R2 or C1 then you will be able to vary the frequency. Or stick a potentiometer in the place of R2.

This link HERE will be able to help you calculate which values to use for your desired frequency.

If you wanted to work it out yourself, you could use the forumula:

f= 1.44/(R1+2R2)C

Although I have found that to be a tad off sometimes! But it gives you a ballpark idea as real world electronics will never be exact!

So, basically, take it apart and rebuild it, this time following a schematic!

P.S make sure you have a working LED!

  • \$\begingroup\$ Thanks for this! However, I found another circuit that only requires one capacitor and I got that one to work. Thanks though :) \$\endgroup\$
    – HXGamer
    Dec 2, 2017 at 17:03
  • \$\begingroup\$ No worries. Glad you got it working! \$\endgroup\$
    – MCG
    Dec 2, 2017 at 17:12

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