5V LED Dimmer Circuit. May 16, 2009 by Received by Email Comments 22. Advertisement. This is a very simple LED dimmer circuit which has 2 transistors, 1 resistor and 2 potentiometers. Typical segment ...

Choosing athree-cell, 4.5V supply results in a lowervoltage of 0.33V per cell. A 4.5V supplycan power as many as eight LEDs.Tests show that this circuit works from4.5V to 0.94V, which is lower than ...

Once the capacitor voltage reaches 5V (or 5.4V as I couldn’t find a 4V3 Zener), the Zener pulls the transistor on and lights the leds. The 3n3 capacitor gives the circuit some positive feedback by ...