AC line LED indicator circuit

If you are looking for a LED display for show AC-line power. This is AC line LED indicator circuit, that is compatible with the AC main power is 115 VAC or 230 VAC. In the circuit diagram, there are 2 LEDs for showing 2 status. First, it shows AC Main or the power grid. Second, show load still hold the power or not. It is nice circuit idea because using a few parts and cheap.

Operation of circuit

AC line LED indicator circuit
AC line LED indicator circuit

It’s a simple circuit. So interesting to learn its working. It is the main indicator of power while not pressing the switch S1. When we feed the 110V-AC to the power cord. The electrical current is flowing through R1, D1, LED1. So makes LED1 light up to reflect the input of the power.

Then, when we press switch S1, the electric current will flow through R2, D2, LED2. It makes LED2 light up instead of LED1. At the same time, some parts of the current flow to bias B lead of Q1-transistor. So, it makes Q1 work to connect all current of LED1 to ground. Makes LED1 go off.

Fuction of components

  • R1,R3 limits the current through the LED1,LED2 to a safe value.
  • D1,D2 rectifier AC to DC to LED1,LED2
  • R2 reduce the preper current to bias Q1

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