One of the questions that hobbyists ask over and over is how to select the value of a current limiting resistor for an LED. Usually the seat of the pants response is: “Subtract 2 V from the supply ...
This is a very simple LED dimmer circuit which has 2 transistors, 1 resistor and 2 potentiometers. Typical segment displays LEDs consume around 25 mA for each segment and should be limited to this ...