Make: Projects
LED Testing
Here are a few tools to make testing LEDs and other things easier. LEDs are so much fun.
LEDs are everywhere and in every project you see anywhere. They show that your microprocessor unit is alive and running the program you wrote. LEDs are tough little lights that light up everything including you. They provide instant gratification. Here is my simple tester. There are lots of kits to show you electronics and soldering and a lot of them use LEDs. Even high-end electronics use LEDs that nobody ever sees to tell a technician that a circuit is working.
Steps
Step #1:
Next
- Build the circuit as shown in the picture. Always wire the pot so that clockwise rotation increases the voltage or lessens the resistance.
- Wiring connections: Ground to LED–; Pot-2 to LED+; Pot-3 to Volts+; DMM to DC Volts; DMM– to ground; DMM+ to LED+.
- Turn the pot counter-clockwise all of the way. Connect power.
- LEDs are Current Devices and they have three states. 1: Lit but dim. Low light voltage. Saves batteries. 2: Lit and steady. Normal brightness. 3: Too bright. You are over-driving them and they will burn out sooner. Lastly, state 4: Too bright and dimming. You have just killed an LED.
- Rotate the pot clockwise until the LED begins to light. You can note this as the lowest voltage that will light the LED. Note the voltage on the DVM. Keep the voltage to less than 2.2 volts for most LEDs.
- Keep watching the LED as you are turning the pot clockwise until the LED brightness is steady. This is your LED’s operating voltage. Turn the pot counter-clockwise to the lowest point where the brightness of the LED is steady. This voltage will make the LED last longer.
- Turn the pot too far and the LED will start to dim. Just turn the pot counter-clockwise until the LED brightness is steady. Keep the voltage at about 2 volts for maximum brightness for most LEDs.
- Some LEDs have a circuit in them that controls voltage and current to the LED. They will not light until they have reached their normal operating voltage. They come on and stay at their normal brightness over a wide range of voltage and current. Usually this is between 4 and 12 volts.
Conclusion
LEDs light the world up and they are easy and fun.
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