meter How to light an LED when a voltage hits a certain point

Posted on Feb 5, 2014

A LED to indicate when a DC voltage reaches 5 volts or more. I don`t want the LED to be dim when it is at 4. 5 or anything. I just want it to be full bright at 5, 0 bright at anything below 5. Is there a way I can do this with discrete components (no IC`s, just resistors, capacitors, transistors etc. ) I do not require the input has the same power source as the meter.

meter How to light an LED when a voltage hits a certain point
Click here to download the full size of the above Circuit.

Why the discrete component requirement I know you want to understand all of this stuff at the lowest level, but this can literally be done with a single op amp, a pot, a resistor and LED. Matt Young May 11 `13 at 20:47 Maybe an op-amp would work, I only have 2 though and I want to build a bunch with different voltages to trigger the LED. I guess I could buy some if an OP-amp has many advantages over other components skyler May 11 `13 at 21:53

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