Resistor value for 2x3x4 water clear led

[Maxusy]

Hi,

I'm planning to build a B.face and I've started sourcing parts. I've bought zealio's from the currently running group buy and I'd like to add 2x3x4 water clear white leds to them.

I was looking at these leds: http://www.ebay.com/itm/100pcs-2x3x4mm-Square-LED-Diodes-Water-Clear-White-Light-Rectangle-Rectangular-/201172207582?hash=item2ed6cc47de:g:vOgAAOSwpDdVWuWV

From the datasheet: forward voltage: 3.0 - 3.4V (I = 20mA) / MCD: 13000 - 15000 (I = 20mA) / Reverse current: 10uA (Vr = 5V)
Would that be a good choice? If so, what resistors should I get to go with them?

From the Winkeyless website:

2012-sized resistors.

820 Ohm : generally used for white/pink LED
910 Ohm : generally used for blue/green LED
1300 Ohm : generally used for red/yellow/orange LED
They are base on 87 keys.
If your PCB is 60% style, the 820-ohm resistor can support all colors.

They offer 1.8mm leds though, so I'm not sure whether this applies to 2x3x4's too.

Another question: what's the reason some people put their 2x3x4 led's under the switch top and others place it above the switch top?

Thanks for the help.

[suicidal_orange]

Welcome to GH, this sounds like a great first build 

From putting the recommended forward voltage (went with 3.2v as it's in the middle) and a source voltage of 5v (USB) with a little trial and error on an LED resistor calculator you can see that a forward current of 2.6mA is about the most you'll get with an 820 Ohm resistor.  A higher resistor value = less brightness, so I would go with the recommended 820 Ohm.  You can always make them dimmer in the firmware but you can't go brighter than the components allow...  It might be worth asking the seller how bright these specific LEDs will be as they're rated for 20mA but most LEDs are and they work fine.

The reason behind putting the LEDs under the switch top is so you can take the top off to swap stems and springs, or to lube them without desoldering the LED.  Also if the LED is outside the switch it may interfere with some keycaps, though 2x3x4s are usually OK for this.  It's worth searching for whichever type of caps you'll be using to be sure as desoldering LEDs is not much fun.

[Maxusy]

Welcome to GH, this sounds like a great first build 

From putting the recommended forward voltage (went with 3.2v as it's in the middle) and a source voltage of 5v (USB) with a little trial and error on an LED resistor calculator you can see that a forward current of 2.6mA is about the most you'll get with an 820 Ohm resistor.  A higher resistor value = less brightness, so I would go with the recommended 820 Ohm.  You can always make them dimmer in the firmware but you can't go brighter than the components allow...  It might be worth asking the seller how bright these specific LEDs will be as they're rated for 20mA but most LEDs are and they work fine.

The reason behind putting the LEDs under the switch top is so you can take the top off to swap stems and springs, or to lube them without desoldering the LED.  Also if the LED is outside the switch it may interfere with some keycaps, though 2x3x4s are usually OK for this.  It's worth searching for whichever type of caps you'll be using to be sure as desoldering LEDs is not much fun.

Thanks for the response, really helpful.

I've placed an order for a dual tone EnjoyPBT blanks set, guess they'll work just fine. (and otherwise I'll have to put the leds inside the switch housing, not too much of a problem)

On the resistor part; thanks for the elaborate explanation! Do you know if there's a certain seller on eBay most people here buy from? I just pasted the first search result.