By Timothy Boyer Updated Mar 24, 2022
Adjusting an LED’s brightness is as easy as using a dimmer on a household lamp. The key component is a variable resistor, called a potentiometer, which lets you fine‑tune the current flowing to the LED. With just a 9‑V battery, a potentiometer, and an LED, you can create a controllable light source in minutes.
Attach one 6‑inch copper wire to the positive terminal of a 9‑V battery. Attach a second 6‑inch wire to the negative terminal. Keep the free ends separate to avoid a short.
Connect the free end of the negative‑wire to the center (wiper) lead of a 100–1,000 Ω potentiometer. The center lead carries the return path from the battery.
Set the potentiometer knob to the middle position before completing the circuit. This prevents a sudden surge of current that could damage the LED.
Attach the free end of the positive battery wire to either the left or right outer lead of the potentiometer. Use the right lead if you want resistance to increase when you turn the knob clockwise; use the left lead for the opposite direction.
Gradually turn the potentiometer knob. Observe the LED brighten as resistance decreases and dim as resistance increases. You now have full control over the LED’s light level.
