Turning a cheap keyboard into a back lit one .

[wickred]

so i got this keyboard [Microsoft G600] and a few LEDs lying around, I tought to myself why not make the keyboard backlit? my idea is fairly simple , connect a few LEDS under the keys , and use the scroll lock button to turn them on and off, Anyone has and idea how to make that happen? i mean without external power source ?

[regack]

You would have to measure to figure out the voltage being supplied to the scroll-lock indicator LED, then string together some lower-voltage-than-that LEDs and resistor groups in parallel and hope you don't exceed the current draw that might have been built into the the indicator LED circuit (if there is any at all...)

Or you could tap directly into the Vcc/GND from the USB, and use the scroll-lock indicator to drive a small relay to power your LED circuit from the direct-usb-power-tap and keep the LED circuit isolated from the rest of the keyboard internals...

[wickred]

Thanks man , the problem is i don't have a voltage o meter [or whatever that is called ] do you know where i can find the standard voltage a keyboard uses and perhaps tap directly into the VCC?

[Hellmark]

Keyboards get supplied 5V, upto 500mA via USB. Most use in the neighborhood of 100mA. Now whether or not things on the keyboard leave it at 5V, or mess with it, is another story.

Long story short, get a multimeter, even if just a cheap one (Harbor freight was just giving them away a week or so ago), and test them. Without tapping into additional power or changing controllers though, I wouldn't bet on being successful.

[wickred]

do you think this one will do the job? http://www.ebay.com/itm/New-Electric-AC-DC-OHM-Voltmeter-Ammeter-Multimeter-Multi-Tester-MF-110A-/271286883025?pt=LH_DefaultDomain_0&hash=item3f29f552d1

[Hellmark]

Yeah, it will. Any multimeter will be fine.