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geekhack Projects => Making Stuff Together! => Topic started by: meepmeep on Fri, 14 July 2017, 10:05:05

Title: Add LEDs to board?
Post by: meepmeep on Fri, 14 July 2017, 10:05:05

Hey All,


I have a PCB which has spots for diodes and nothing for LEDs. I'd like to add LEDs to the top of the board rather than diodes. So am I right in assuming I can wire in the LEDs + resistors, and I think I need a mosfet too?  Please help with any info you may know. I'm fairly good with electronics but its the putting a solution together part I need help with. What's nice is the diode location is in-switch so I have room to just slap an LED in instead. and my plan would be to just hand wire a resistor to the leg of the LED.

I'm planning on using a Teensy2.0 and also have ws2812b lighting below. It's such a perfect board I wish I could have that top layer of LEDs.

Title: Re: Add LEDs to board?
Post by: Findecanor on Fri, 14 July 2017, 10:22:56

It does not sound like it is something easily done.

If the keyboard PCB was designed for diodes then diodes would be connected to the switches and needed for the keyboard to function. Each diode is supposed to be in series with a switch at a junction in the keyboard matrix.
Keyboard LED behind keys are usually driven not with direct current but with PWM, with different banks of LEDs lit at a time, so as to not overload the 500 mA current limit of USB 2.0.

Title: Re: Add LEDs to board?
Post by: SpAmRaY on Fri, 14 July 2017, 10:55:55

It would also be helpful if you told us what PCB you have or even provide some photos to see clearly what you would be working with.

Title: Re: Add LEDs to board?
Post by: meepmeep on Fri, 14 July 2017, 11:22:07

Its an i75,

https://github.com/di0ib/tmk_keyboard/tree/master/keyboard/i75_ProMicro/pcb (https://github.com/di0ib/tmk_keyboard/tree/master/keyboard/i75_ProMicro/pcb)

Also seen here with pictures:
http://www.40percent.club/2016/11/i75.html (http://www.40percent.club/2016/11/i75.html)



AHH yeah I think I get it how the diodes really are separate from the circuitry of the lighting. So simply wiring in lighting is totally not the right idea. To make it happen on this board I see that I'd have to hand wire in the entire LED grid and possibly undermount the diodes so I can put LEDs in the switches. So really I've considered making my own PCB from scratch, or waiting until I can find a 75 or 96 key ortho.

Title: Re: Add LEDs to board?
Post by: SpAmRaY on Fri, 14 July 2017, 11:26:45

I had no idea that board existed....I'd put that PCB up on the wall as decoration. :D

It's like everything else keyboard....there is almost always a way but the specific route you wanted to go wouldn't be feasible.

Title: Re: Add LEDs to board?
Post by: meepmeep on Fri, 14 July 2017, 11:41:22

Yeah I love it!

I went with an acrylic sandwich case, with clear acrylic so it can be seen.