Concept of Operation

The circuit demonstrates the use of a potentiometer to control the brightness of an LED. A potentiometer is a three-pin device that provides an adjustable voltage divider. The voltage at the center pin changes as the knob is rotated. When the knob is rotated clockwise the LED becomes brighter, when the knob is rotated counter-clockwise the LED becomes more dim.

Schematic

Breadboard Diagram

Parts

• 50K Potentiometer (x1)
• 330 Ohm Resistor (x1)
• Standard LED (x1)
• Slide Switch (x1)

(All parts for the project are available in our store.)

Notes on Implementation

1. LEDs are polarized and must be mounted in the proper orientation. On standard, round LEDs, the cathode (negative lead) is identified by a flat edge. Also, the cathode lead is typically shorter than the anode.
2. The schematic shows a single-pole single-throw (SPST) switch between the power supply and the circuit. Our kits often include a three-pin single-pole double-throw (SPDT) "breadboard friendly" slide switch. An SPDT switch can be used here by aligning two adjacent pins with rows 10 and 11 on the breadboard. The breadboard diagram show pins 2 and 3 being used.
3. The circuit was built and tested at 4.8 volts DC (4 AA NiMH rechargeable batteries). Any power source that supplies about 5v DC should work fine.