# Very Basic 555 Timer oscillator not working

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!

• Most likely wire contact or wiring error. Commented Dec 2, 2017 at 0:28
• Can you add a schematic to your question, there is a built in tool? Commented Dec 2, 2017 at 0:29
• 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. Commented Dec 2, 2017 at 0:29
• Maybe the LED was burnt out from putting in backwards at >5V Commented Dec 2, 2017 at 0:31
• Are you sure you've got the capacitor connected with the correct polarity? Commented Dec 2, 2017 at 4:53

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:

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.

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!

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