geekhack
geekhack Projects => Making Stuff Together! => Topic started by: Zuve on Tue, 01 October 2019, 00:56:58
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Been looking into designing a PCB with RGB per key backlighting. I'm starting with a numpad to keep things a bit more simple, but intend on(hopefully) designing a 60% PCB in the future. Curious if anyone has insight into how wireless keyboards manage to power their RGB. I've seen advertisements of up to 14 hours of battery life with RGB on wireless keyboards. Perhaps I'm missing something obvious, but every RGB LED I've seen seems to have a maximum current draw of at least 30mA. Multiply that by 61 keys, and you have 1830mA peak draw. How would one power that via a battery for so long? I imagine I am missing something, because I doubt these keyboards have the over 5Ah battery that would be required for just 3 hours with all LEDs on.
Thanks!
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I do not think that they are using LEDs at their full power, 30mA per key would be extremely bright. I guess they only go up to 1mA or maybe even less with high efficiency LEDs (i can only guess as i do not have any RGB or wireless keyboards to test).
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I don't think you're missing anything. Laws of physics still apply, so it's a simple equation - battery life = battery capacity / power draw.
You mentioned peak draw - but LEDs need way less to shine enough. So I guess for decent battery life the draw must be set pretty low.
Still, even at 5 mA per LED * 60 = 300 mA, a 2000 mAh battery would last around 6 hours, so not sure how anyone can claim 14 hours with RGB. Well, the only way is low LED current and big battery :)
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Like laptops they probably rate it at the lowest brightness setting.