Two LED Blinky
This is the simplest circuit to make two LED blink back and forth. The technical term for this circuit is “astable multivibrator”.
It’s really easy to put together, with only 10 parts.
[Part List]
- 2 x LEDs – any color. Red, yellow, green, blue…
- 2 x NPN transistors – just about any small transistor. I used PN2222A, but you can use 2N3904, 2N4401, etc.
- 2 x Capacitor – around 10 – 22 uF, 6V or higher than power supply voltage. Electrolytic capacitors are the easiest to find. The larger the capacitance the slower the blinking.
- 2 x 220 ohm resisters – anything from 200 to 1k ohm of any type should work.
- 2 x 47k ohm resisters – anything from 22k to 100k ohm should work. Value of these changes the timing of blinking (larger the value, slower the blinking).
You can easily obtain the parts from your local Redioshack.
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In the circuit above, I think that the polarities of the tow capacitors are not true as indicated. I mean that for left one(for example), the polarity should be (-,+) not as indicated in the circuit..
March 1, 2017 at 4:29 pm
What size capacitors and resitors are you using in the video?
October 22, 2012 at 8:44 pm
Same as the values on the schematics – 47k ohm and 10uF for the timing.
October 23, 2012 at 2:25 am
Tried it with BC637 x 2, 33K x 2, 68 Ohm x 2, 2 x bright white LED, 2x 10uF and a 3,7 v cell phone Lithium battery. Works really well! Bright too!! Epileptic warningz!
July 5, 2012 at 5:09 pm
can u send a picture from other side? we cant see the how to put the resisters there?
February 20, 2011 at 11:34 am
Hello,
I’ve posted the circuit schematic, so you can see the connection and values of the parts.
Thanks,
Aki
February 25, 2011 at 12:11 pm