Author Topic: Schematic for keyboard backlight  (Read 4608 times)

0 Members and 1 Guest are viewing this topic.

Offline clickclack123

  • Thread Starter
  • Posts: 357
  • Location: Australia, Mate!
Schematic for keyboard backlight
« on: Fri, 28 February 2014, 06:16:20 »
With led's being so cheap, I want to make a keyboard with backlighting, preferably a single led on every key...

Anyone know where there's a schematic for a circuit for a keyboard with backlighting?

I'd like it to be dimmable. Just dimmable with a pot is fine, nothing fancy.

Offline Findecanor

  • Posts: 5035
  • Location: Koriko
Re: Schematic for keyboard backlight
« Reply #1 on: Fri, 28 February 2014, 15:05:40 »
You could Google for "LED Matrix Arduino" to find code and schematics for LED matrices powered by Arduino boards (AVR microcontroller). That info should give you the basics.
There are also driver chips for LEDs. Search for "LED driver".

You will need a matrix that strobes the LEDs very fast, because having all LEDs lit all the time would draw too much power for USB. Also, not all types of LEDs are suitable.

Offline clickclack123

  • Thread Starter
  • Posts: 357
  • Location: Australia, Mate!
Re: Schematic for keyboard backlight
« Reply #2 on: Fri, 28 February 2014, 17:53:28 »
You could Google for "LED Matrix Arduino" to find code and schematics for LED matrices powered by Arduino boards (AVR microcontroller). That info should give you the basics.
There are also driver chips for LEDs. Search for "LED driver".

You will need a matrix that strobes the LEDs very fast, because having all LEDs lit all the time would draw too much power for USB. Also, not all types of LEDs are suitable.

Thanks, the best page I've come across yet is http://blog.komar.be/gh60-evolution/. I hadn't really thought about it fully, backlighting might require more complexity/cost than I'm willing to put into it.


Offline clickclack123

  • Thread Starter
  • Posts: 357
  • Location: Australia, Mate!
Re: Schematic for keyboard backlight
« Reply #4 on: Fri, 28 February 2014, 22:29:16 »
Deck published a couple of full schematics...
http://www.deckkeyboards.com/support/deck-82-schematic
http://www.deckkeyboards.com/support/deck-legend-schematic

Thanks for the pointer, soarer. That's exactly what I was looking for, but I still don't really get how that backlighting works. Seems like the circuit is overly complicated for a keyboard?

Offline mkawa

  •  No Marketplace Access
  • Posts: 6562
  • (ツ)@@@. crankypants
Re: Schematic for keyboard backlight
« Reply #5 on: Sat, 01 March 2014, 00:37:40 »
the PWM code is what matters; the schematic is fairly uninteresting.

to all the brilliant friends who have left us, and all the students who climb on their shoulders.

Offline Soarer

  • * Moderator
  • Posts: 1918
  • Location: UK
Re: Schematic for keyboard backlight
« Reply #6 on: Sat, 01 March 2014, 07:04:24 »
Those Decks do not use PWM! Six outputs used, with those resistor values... it's a cheap-ass DAC :D

The main point is, without using PWM, you need some active buffer. In the Deck circuit, those six diodes and resistors could be replaced by a simple pot, and the transistors serve as a buffer between it and the LEDs.

Even if you do use PWM, you still need a high current output which a typical microcontroller cannot provide. So again you'd need a buffer or to use some dedicated chip.