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Need help, uneven backlight on a QMK converted chinese keyboard
nevin:
without knowing the specs of the leds or the the circuitry in the original pcb... it's a bit of a guessing game.
even though the differences don't seem to be a lot, they are a big difference at these voltages.
you probably need some kind of driver circuit to support all the leds.
there are also a couple ways to connect the leds.
- with pin acting as positive
- with pin acting as ground, driving the positive off of vcc or raw
(again, depends on current draw and the specs of your leds. drive too much current to them and you'll burn them out, not enough and they'll be dim/weak)
do some research into what the teensy is capable of outputting
spec sheet https://www.pjrc.com/teensy/at90usb1286.pdf
also check the QMK documentation
https://beta.docs.qmk.fm/using-qmk/hardware-features/lighting/feature_backlight
(even through they are on the top, they function as backlight)
example: this is what keeb.io uses to support underglow for their boards (not that this is exactly what you need, just an example)
https://keeb.io/collections/frontpage/products/led-support-components-add-on
andresteare:
--- Quote from: nevin on Mon, 25 January 2021, 09:15:50 ---without knowing the specs of the leds or the the circuitry in the original pcb... it's a bit of a guessing game.
even though the differences don't seem to be a lot, they are a big difference at these voltages.
you probably need some kind of driver circuit to support all the leds.
there are also a couple ways to connect the leds.
- with pin acting as positive
- with pin acting as ground, driving the positive off of vcc or raw
(again, depends on current draw and the specs of your leds. drive too much current to them and you'll burn them out, not enough and they'll be dim/weak)
do some research into what the teensy is capable of outputting
spec sheet https://www.pjrc.com/teensy/at90usb1286.pdf
also check the QMK documentation
https://beta.docs.qmk.fm/using-qmk/hardware-features/lighting/feature_backlight
(even through they are on the top, they function as backlight)
example: this is what keeb.io uses to support underglow for their boards (not that this is exactly what you need, just an example)
https://keeb.io/collections/frontpage/products/led-support-components-add-on
--- End quote ---
Thank you! I have a lot to research then, can I contact you if I have any doubts in the future? :)
nevin:
sure.
you probably just need a driver circuit.
might be able to get away with driving them from vcc, through driver circuit, using the pins as the ground to turn the rows on & off
andresteare:
--- Quote from: nevin on Mon, 25 January 2021, 10:26:18 ---sure.
you probably just need a driver circuit.
might be able to get away with driving them from vcc, through driver circuit, using the pins as the ground to turn the rows on & off
--- End quote ---
one of these per row would do the trick?
nevin:
that would be overkill, but on the right track.
...you could probably use that one little board to drive the leds for the whole board.
i wish we knew the specs on the leds that are used in your board... voltage, current draw....
- sometimes different single color leds are driven at different voltages/current.
- i don't think you said.... but what's the brand/model of keyboard you're modifying?
i'll do some digging and see what i can come up with for you.
some info for starters....
https://geekhack.org/index.php?topic=55338.0
from link above:
--- Quote ---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.
--- End quote ---
and you can read some of komar's explanation of how he was thinking of implementing it in the GH60
http://blog.komar.be/gh60-evolution/
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