LED Pilot Light scheme Tags - Circuit Schematic Diagram https://circuitscheme.com/tag/led-pilot-light-scheme Electroni Schematic and PCB Design Fri, 28 Aug 2020 15:00:59 +0000 en-US hourly 1 https://circuitscheme.com/wp-content/uploads/2016/10/cropped-ecd-32x32.jpg LED Pilot Light scheme Tags - Circuit Schematic Diagram https://circuitscheme.com/tag/led-pilot-light-scheme 32 32 129959653 LED Pilot Light using FET https://circuitscheme.com/led-pilot-light.html https://circuitscheme.com/led-pilot-light.html#respond Fri, 28 Aug 2020 15:00:59 +0000 http://circuitscheme.com/?p=822 This is the LED pilot light (or LED indicator) circuit. LEDs (Light Emitting Diode) part are interesting things. They only operate at DC supply within specific tolerances, and generally connected with a current limiting resistor towards […]

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]]> This is the LED pilot light (or LED indicator) circuit. LEDs (Light Emitting Diode) part are interesting things. They only operate at DC supply within specific tolerances, and generally connected with a current limiting resistor towards the power source. Rather than a resistor, it is possible to use a FET (Field Effect Transistor) like the ECG31 and, NTE312 (you may try other types).

LED pilot light circuit with FET

When the gate and the source are connected together, it acts as a current regulator.

In the circuit above, the current is constant between 6 and 8 mA at 5 to 30Vdc. If the diode is added (the 1N4148 is optional), this circuit is secured agains polarity reversal and can be connected to a AC power supply of 5 to 20 VAC.

LED Pilot Light using FET, circuit designed by Tony Van Roon

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