Soldering LEDs to pok3r

Plasmodii

25 Jan 2016, 10:48

Hello guys, after swapping a few of my chattering switches with new ones, I realised that soldering is not that hard and want to customize my pok3r a bit. My question is about the type of LEDs I have to use. The ones I have got my eyes on have the following specs:
-3mm wide
-viewing angle 330
-brightness 4-4.4lm
-working current 20mA
-voltage 2.6-3.6
From what I know USB 2.0 can only output 500mA and 67 LEDs will require much more. I am also wondering if the viewing angle will have any impact on how the backlight looks and if 4lm is too bright.
I will be very grateful if anyone can give me some advice!

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flabbergast

25 Jan 2016, 10:58

About the current: 20mA is the maximum that can flow through a LED and not burn out. In practice there are resistors in series with the LEDs on the PCB that limit how much current goes through. Depending on the values of those, the maximum current is usually much lower than 20mA. (There are some measurements here, not Pok3r though. But the figures for Poker II shouldn't be much off, it's the same manufacturer.)

Don't know about the other questions.

Plasmodii

25 Jan 2016, 12:37

Thanks for the reply! So you are saying that the LEDs will work just fine but won't be as bright as they can be?

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flabbergast

25 Jan 2016, 12:43

Yes. This is "normal", i.e. pretty much in all the products that are not primarily "lights" (as in a lamp) that I've seen, the current is limited to something like 1-4mA. BTW you can compute the amperage by reading the values of the resistors on the PCB (those are usually small black rectangular SMT parts, the ones that are not diodes and there's a lot of them, usually one for each switch), googling what the code on the part means (google "smt resistor codes", I would expect the result to be something in the range 330 Ohm - 1 kOhm ), and then using a LED calculator.

Also, lowering the amperage through a LED usually extends its lifespan.

Matt_

25 Jan 2016, 15:56

Wider viewing angles will help light large legends more uniformly. For instance here the LED under the Capslock keycap has a rather narrow viewing angle, so the legend is only lit in the center:

Image

And indeed you don't need to feed 20 mA to your LEDs. My Pure Pro is blindingly bright when the backlight is pushed to the max — with only 3.6 mA per LED (560Ω resistors).

Plasmodii

25 Jan 2016, 22:48

Thank you all for the responses!

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