I have a CM storm Trigger with blue Cherry MX, it's a good keyboard that I got a few years ago and still works perfectly. My only problem is with the backlighting, since my setup is now mostly white/black/wood and the red is not looking good.

I'd like to switch to white LED backlighting, I thought I could buy a pack of white 3mm LEDs and solder them in place of the red ones. I'm concerned about forward voltages, red diodes are usually ~2V and white ones are ~3V.

Many thanks.

  • \$\begingroup\$ Most likely the internal LEDs are SMD ones, not 3mm ones. Are the original RGB or single color? As for voltage drop, can you check if the original ones have a series Resistor? If so you can calculate the current and check if the ones you are replacing with are ok for this use. \$\endgroup\$ – Wesley Lee Nov 21 '16 at 0:34
  • \$\begingroup\$ They are 3mm ones like this picture vortez.net/index.php?ct=articles&action=file&id=12214 I'm afraid I don't have the tools to do measurements, I want to know if theoretically it can be done. \$\endgroup\$ – tototoru Nov 21 '16 at 0:43
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    \$\begingroup\$ If they ran the LEDs in series pairs to save power then white LEDs won't work. If they are individual with one resistor each it might work okay enough (the white LEDs will draw less current but might be bright enough). How are you going to unsolder the LEDs without damaging the PCB? It might be better to sell your keyboard and buy a new one. \$\endgroup\$ – Spehro Pefhany Nov 21 '16 at 0:46
  • \$\begingroup\$ Thanks, I didn't open the keyboard yet to know if they are in series or in parallel. It sounds like a cheap mod, also I like this keyboard because it has macros and doesn't look aggressive like other gaming keyboards. \$\endgroup\$ – tototoru Nov 21 '16 at 0:59

You are right about diode forward voltage. There are three common ways to drive the diodes:

  • 5V with resistor: this is how most indicator diodes are wired. In your case, white LEDs will be less bright but since they are also more efficient, overall light output may be about the same.
  • 3.3V with resistor: white LEDs will not work, but this setup is unlikely as it will put extra load on 3.3v regulator for no reason.
  • In series with CC LED driver: this is how LEDs are driven in monitor backlights. This provides very uniform brightness but requires more parts. May or may not work depending on the driver IC used: for example, if each chain has 10 LEDs, and driver is rated for 24V max, then this will work with red leds (20v total) but not with white leds (30v total). But if they only put 7 LEDs per chain, then this driver will work.

Overall, I recommend opening up a keyboard and looking at the design. If you see a small IC with inductor next to it, let me know the part number.


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