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how to use a simple 2V LED in High voltage circuit? Answered

Hi! I have 100V 0,5A DC circuit and a simple  2V 0,02A LED, what shall I do if I want the LED to shine but not to burn it. Thanks!

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steveastrouk

Best Answer 3 years ago

2W 5K resistor in series with the LED. The resistor will get warm !

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Josehf Murchisonsteveastrouk

Answer 3 years ago

I would go with a three watt but you must admit that is a voltage divider circuit?

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Downunder35m

3 years ago

What about quick and dirty?
3 common diodes in series will have a voltage drop of around 2.1V.
A LED in parallel to these diodes and with a 100Ohm resistor should do the trick.
All you have to do is find a spot for the three diodes where their voltage drop does not cause a problem, althoug I think less than 3V on a 100V rail is not too bad.
You still need a load on the high voltage output for it to work though.

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steveastroukDownunder35m

Answer 3 years ago

What limits the diode forward current ????? You still need dropper resistors.

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Downunder35msteveastrouk

Answer 3 years ago

That's what the 100Ohm resistor is for.
The LED is in parallel t the diodes, so the LED only get's around 2.1V - a 100Ohm resistor should be sufficient.
Keep in mind we are not using the full voltage, only the voltage drop along the normal diodes ;)

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steveastroukDownunder35m

Answer 3 years ago

No, you have the 2.1V drop of the three diodes, but where is the limit resistor for the current in THEM ?

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Downunder35msteveastrouk

Answer 3 years ago

Why would I want to limit the current through the diodes?
They are in line with the output so that would be a bad thing...

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IgorsS

3 years ago

Thank you all! I think I will go with the resistor to start with.

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Josehf Murchison

3 years ago

Yea but you will need a step down of some kind ether a step down that uses a voltage divider or a DC to DC converter circuit whatever circuit you use don't surpass 0.02 amp.