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Blinking LED for Diesel Generator


New Member
I need one small circuit which can be placed at the back of a switch board. The functionalities will be as follows.

1. There are 2 supply lines (220v), (A) and (B), where (A) is active in case when power supply is there OR diesel generator(DG) is running. B) is active in case when ONLY power supply is there.

2. One LED indicator (LED attached with resistance) will be there which will BLINK if generator is running, i.e. (A) is active and (B) is inactive, and will glow STEADY if generator is not running, i.e. both (A) and (B) is active.

It would be great if you can help me out.


Well-Known Member
Most Helpful Member
What do you want the LED to do if B is active and A is inactive?

I would suggest that you connect of-the-shelf 220 V ac to 5 V or 12 V power supplies to the supplies. You can then work on the 5 V or 12 V signals which will turn on when the 220 V supplies are active, but they will be isolated and safer than connecting to the mains.

schmitt trigger

Well-Known Member
A truth table is the best way to describe a logical problem.
Then using minterms you can solve the equations that describe the system behavior.
Meaning that for certain input combinations you expect certain output states.

Therefore please write a truth table. Your verbal description is confusing.

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