Potentiometer LED Dimmer

Application

This circuit uses the Potentiometer as a front-panel brightness control for a current-limited Green LED. It is configured as an interactive operating point demo so moving the wiper updates the table values and the LED symbol immediately.

Design Context

The 5 V source is applied across RV1. The wiper drives RLED and D1, so the LED receives more voltage and current as the wiper moves toward the high side of the divider. RLED limits current when the wiper is near the top of its travel.

Expected Behavior

At low wiper positions, Vwiper is below the LED forward voltage and Iled should be near zero. As the wiper position rises, Vwiper increases and the Green LED begins to conduct. The table should show Vwiper and Iled increasing, and the LED symbol should brighten as simulated forward current increases.

Key Values

• Simulation mode: interactive operating point
• Supply: 5 V DC
• Potentiometer: 10 kOhm, starts at 75%
• LED resistor: 330 ohm
• Measured values: Vwiper and Iled

Suggested Experiments

• Drag the wiper from 0% to 100% and watch where the LED begins to turn on.
• Change RLED to 1 kOhm and compare the LED current and brightness.
• Change the supply voltage to see how much headroom the LED branch needs.

Featured Component

The Potentiometer is a three-terminal adjustable divider. In this circuit the wiper acts as a variable control voltage that directly changes the LED branch current.