Wednesday, January 10, 2018

Mains Powered Simple Blinking LED

This diagram might not be that useful for what it is but it teaches the use of an interesting component called DIAC.

So what this circuit does is blink an LED and can be hooked up directly to AC main line and it needs only a few components.


1 47kΩ
1 220Ω

1 47µF 63V

1 1N4007

1 DB3


How Does it work?

When power is turned on the 47µF capacitor starts to charge via the 47kΩ resistor and 1N4007  diode. As soon as the voltage hits the break over voltage of the DIAC DB3(Which is 32V, more information in the datasheet linked below) it starts to conduct and the LED lights up.

As the current is passing through the LED now it empties the charge stored in the capacitor faster than what the 47kΩ resistor can provide so soon enough current through the DIAC falls to a point when it will just stop conducting. Thus the LED turns off.

Then the whole process repeats again giving us a blinking LED.


1. Remember that even if the DIAC was triggered with a certain voltage it will keep conducting unless the current through it falls to a certain value. Once triggered, even if the voltage falls below break over voltage it will still conduct.

2. 47kΩ resistor and 47µF capacitor can be altered to control the blinking frequency.

3. This circuit is not mains isolated so to avoid electrical shock do not touch any part of the running circuit.


1. Datasheet for DIAC DB3.
2. More about DIAC.
3. Visit my full blog.

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