Blog

Nov 03, 2024

This Simple Device Will Help You Pair Your LEDs with the Ideal Resistors - Hackster.io

One of the first lessons that makers learn, when running that initial “blink” code on a microcontroller, is that LEDs have to be paired with resistors. Otherwise, the LEDs will draw more and more

One of the first lessons that makers learn, when running that initial “blink” code on a microcontroller, is that LEDs have to be paired with resistors. Otherwise, the LEDs will draw more and more current until they burn out — a process that is almost immediate. But a resistor also reduces voltage in the circuit, which can make the LED dimmer than you might want. A good balance is key, and this simple device designed by Leethayer8 will help you pair your LEDs with the perfect resistors.

For simplicity’s sake, you may have seen project authors say to use any resistor, between say 100 ohms and 10k ohms, to limit the current of an LED—I’ve written such instructions, myself. But the resistor’s value does make a difference. A higher value lowers the circuit voltage, dimming the LED and drawing less current. The opposite is also true. So, you want a resistor with a value that yields the LED brightness and power consumption that you want.

This device helps you identify that resistor value. By moving a small jumper between header pins, you can select the resistor that connects to the LED you place in the socket. As designed, it gives you seven different resistors with values from 220 ohms to 10k ohms. It works with 5V LEDs in the standard through-hole package (one cathode leg, one anode leg). By swapping out some of the components, you can make this device work with 3.3V LEDs instead or with different resistors.

Leethayer8 designed the device to be as easy to assemble as possible. It uses a simple two-sided PCB and uses only through-hole components that are very easy to solder. There is even a switch to engage a 5V voltage regulator, in case you want to use a 9V-12V power supply. If you’re using a 5V power supply, that isn’t necessary.

And as a bonus, there is one final function: a test point for a multimeter. That gives you an easy way to put a multimeter inline with the LED circuit, so you can measure the total current draw with a specific LED and resistor combo.