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Author Topic: Led's voltage?  (Read 4007 times)

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Offline ianxblog

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Led's voltage?
« on: Sat, 22 February 2014, 05:18:36 »
Hello.

I may want to replace leds on my keyboard, I'm talking about the Caps-num-scrl leds, it's not backlit.

What LEDS should I use? 2, 3, 5v? 20ma? Does ma matters?
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Offline Hyde

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Re: Led's voltage?
« Reply #1 on: Sat, 22 February 2014, 23:00:02 »
Uh what's the current LED color on your keyboard now?  Typically white and blue use higher voltage and the rest of the color use lower voltage.

So for example if your keyboard currently has white or blue LED, chances are the resistor on it uses a higher voltage.  If you swap to an LED with lower voltage then it will shorten the life of LED (since it's too strong).

In the reverse case, then your white or blue LED will just bit a bit dim (since not enough voltage).

But in the real world scenario, LED are typically pretty cheap and it generally also will still work within a range anyway.  So I'd say don't worry too much about it.

:P
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Offline dorkvader

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Re: Led's voltage?
« Reply #2 on: Sat, 22 February 2014, 23:57:46 »
you also dont want it to be too bright. The max current rating of the LED matters little since the KB is likely only flowing like 1ma through the indicator leds when they're on.

You do need to worry about that resistor though: if your indicator LEDs are too bright, it'll light up the whole room at night. Ask anyone with a WASD V1 about it.

what KB is it? changing the LEDs and resistors might be easy or hard depending. For example, aforementioned WASD V1 has surface mount resistors on the controller PCB: changing them out is a real pain.

also: I recommend white LEDs which can be coloured to your preferred tint with a marker. If you want to change colours, they are easy to wipe off once the case is removed.
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Offline ianxblog

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Re: Led's voltage?
« Reply #3 on: Sun, 23 February 2014, 00:23:31 »
The leds are orange/yellow. It's a Chicony KB-5161.
The PCB isn't that complicated, but I would prefer desoldering and soldering just LEDs.

The leds are like this:

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Offline dorkvader

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Re: Led's voltage?
« Reply #4 on: Sun, 23 February 2014, 00:32:33 »
Quote from: ianxblog on Sun, 23 February 2014, 00:23:31
The leds are orange/yellow. It's a Chicony KB-5161.
The PCB isn't that complicated, but I would prefer desoldering and soldering just LEDs.

The leds are like this:

Show Image


the size of the LED doesnt matter too much, but the colour does.

If you plan to replace them with a similar colour (orange / red) then the forward voltage of the LED is ssimilar and they will be replaceable.

If you want to put in a different colour like blue, green or white, the voltage is very different and you should consider replacing the resistor as well.

Although, a higher Vf LED like a blue, green or white will also likely be brigher, this will compensate somewhat for the lower current running through it (about half) when compared to a red/orange/yellow LED.

Then again, it's hard to guess the Vf of an LED in an old KB. LEDs have changed a lot. DO you have a multimeter to read the Vf of the LED?

---
To make a long post short: it probably won't matter but if you install them and you don't like how dim or bright they are: you'll have to swap resistors or colour over them with a marker. If you want to be sure up front that the replacements will work, get ones with teh same forward voltage drop and luminous efficacy as the ones you're replacing.
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Offline ianxblog

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Re: Led's voltage?
« Reply #5 on: Sun, 23 February 2014, 01:27:39 »
Quote from: dorkvader on Sun, 23 February 2014, 00:32:33
Quote from: ianxblog on Sun, 23 February 2014, 00:23:31
The leds are orange/yellow. It's a Chicony KB-5161.
The PCB isn't that complicated, but I would prefer desoldering and soldering just LEDs.

The leds are like this:

Show Image


the size of the LED doesnt matter too much, but the colour does.

If you plan to replace them with a similar colour (orange / red) then the forward voltage of the LED is ssimilar and they will be replaceable.

If you want to put in a different colour like blue, green or white, the voltage is very different and you should consider replacing the resistor as well.

Although, a higher Vf LED like a blue, green or white will also likely be brigher, this will compensate somewhat for the lower current running through it (about half) when compared to a red/orange/yellow LED.

Then again, it's hard to guess the Vf of an LED in an old KB. LEDs have changed a lot. DO you have a multimeter to read the Vf of the LED?

---
To make a long post short: it probably won't matter but if you install them and you don't like how dim or bright they are: you'll have to swap resistors or colour over them with a marker. If you want to be sure up front that the replacements will work, get ones with teh same forward voltage drop and luminous efficacy as the ones you're replacing.

Shouldn't I just stick with any color 3v (for example) led? I don't really mind brightness amount.
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