# Backlighting And RGB ##### Bling bling. ## QMK-Compatible LED backlighting This is one LED per switch. The structure is:
``` . |- LED --- Resistor -| | | N-Channel 5V ---|- LED --- Resistor -|----- MOSFET ----- GND | | | |- LED --- Resistor -| PWM PIN ``` - Use a N-channel MOSFET. - A PWM pin can only deliver around 20mA absolute maximum. Drawing tons of LEDs from a single PWM pin will easily fry your microchip. Place a resistor between the PWM pin and MOSFET gate. - All LED-Resistor pairs are placed in parallel. - All LEDs can be run under a few or single resistor, but this leads to brightness inconsistencies among the LEDs. - The current from the LED-Resistor pairs feed into the drain of the MOSFET. - PWM feeds into the gate of the MOSFET with a 100~1k or so resistor, usually. - Source of the MOSFET goes to ground. - Each LED resistor should be planned to let around 1-5mA through the LEDs each. 20mA will hurt your eyes.
### Choosing the correct MOSFET #### Power Dissipation
- Make sure the current flowing through times the voltage drop doesn't lead to a power dissipation that doesn't fry the MOSFET.
#### Maximum voltage and current
- Check for Drain-Source voltage/current max ratings.
#### Size
- Do not pick a MOSFET which will not fit on your PCB. ---
RGB Underglow WS2812B is the standard used for underglow.
- Draws 45-50mA per package maximum. - However, AliExpress GH60 PCBs have 16 WS2812B. - Current can be limited via QMK. - Can be daisy-chained together. One LED passes data onto the next, and so on. - Can be purchased in individual WS2812B or by strips. Use individual for assembled PCBs. - Wired in the following way: - VDD to 5V - VSS to GND - DIN to previous LED DOUT, or AVR pin if first LED - DOUT to next LED DIN, or unconnected if last LED - Placing a 500 ohm resistor between AVR pin and first LED is highly recommended
### Various other RGB choices WS2812 (without B) - Unsimplified version of WS2812B with 6 pins WS2811 - The controller within WS2812B. Can be used as standalone controller with other RGBs. Controller-less RGBs - Use with separate PWM LED controllers. WS2812C - Low current variant SK6812 - An alternative that also works with QMK --- # Indicator LEDs Simplest.
``` MCU PIN --- LED --- Resistor --- GND (Source setup - Toggle pin high to turn on)



or



5V --- LED --- Resistor --- MCU PIN (Sink setup - Toggle pin high to turn off) ```
LED and resistor can be swapped.