Led Beneath Keys Or Nubs? Or Will That Be To Hard?

[borgqueenx]

I know im not technical, but my brother is, and i can ask him to watch this forums a bit.
Im interested in putting a red or blue led beneath the nubs, and maby white leds beneath the keyboard and other keys.

Think this is an option, or will it be to hard?

btw: yes i know this has been discusses earlier, but i couldnt find the thread or posts anymore.

 

[kingoddball]

Easy as anything else that requires soldering!
Its two simple brass pads!

Find the right LED that you want, place it, heat up a soldering iron, tin the end and solder it down! WALA!

Edit:
MWestern will be able to help more but: I'm sure you would be able to chain a few LED's together off the same pad as well.
I wouldn't go over board with running many off the one set.

 

[atomicthumbs]

you need resistors or the LEDs will burn themselves out; current limit on available solder pads might not be enough for more than one and/or high-brightness LEDs; pads might not be where you want them; keys aren't transparent

people with hardware details might be able to help you with limitations; use wires for extending; buy a new keypad or modify existing one (exacto knife?)

 

[borgqueenx]

there is space enough for all the parts needed beneath the keymat?

 

[Fishbong]

There should be more than enough space for a few SMD LEDs but the real problem is that the Pandora keymat is not transparent.

 

[greendots]

The only option for lighted key I could think of involves lots of tiny fiber optic wires.

I would love to see RGB SMD LEDs and a transparent keymat in a future version of the pandora though. And to have all other LEDs be RGB as well.

 

[Sander Hoksbergen]

there is space enough for all the parts needed beneath the keymat?

SMD Led + SMD Resistor + 32 awg wire = Tiny. You would need a resistor(about 1-1.5x the LED size) per LED though. (I will shoot the next person to suggest putting all LEDs in parallel)

.
Most SMD leds are also wtfomgbbq bright.

But yeah....Keymat isn't transparant.

 

[kagato]

You're not going to be able to backlight the letters on the keys without a new keymat.

But if you're just looking for some illuminated bling on your Pandora, you might be able to light up the key frames a bit like this (ignoring the lit labels):

Position some LEDs around the edge of the keymat facing inwards to illuminate the top surface of the keymat. You'd hopefully get a bit of glow around each of the keys (more at the edges than the middle, of course).

At least you can test it out without destroying any parts on your Pandora

 

[kingoddball]

you need resistors or the LEDs will burn themselves out; current limit on available solder pads might not be enough for more than one and/or high-brightness LEDs; pads might not be where you want them; keys aren't transparent

people with hardware details might be able to help you with limitations; use wires for extending; buy a new keypad or modify existing one (exacto knife?)

Doesn't the board run at 3.8v(or 4v'ish)?

An LED can run fine at 3-4v and won't burn out very fast.
You can chain more than one LED off 3v.

Resisters are a good idea, but should not be nessessary... Besides, If I remember correctly, there are already resistors ON the board for these LED pads.

 

[peca]

Resisters are a good idea, but should not be nessessary... Besides, If I remember correctly, there are already resistors ON the board for these LED pads.

I doubt that resistors are there:

KP BL = Keypad backlight (I just put it on the bottom to be clear of the membranes on top and it has no use for us right now, just another hacker's tool not recommended for average users. Placing a couple of pads on a PCB and actually designing buttons that can pass light through are two completely different things so please don't criticize why I would put them on there to tempt fate)

One pad connects to the battery and the other to a ball on the power management chip that provides a current sink for up to 160mA. It has PWM control for brightness variability so it was designed for specifically driving LEDs. It's not best designed for an LCD backlight because each LED requires its own current limiting resistor and all are connected in parallel so guaranteeing brightness uniformity is not as good as a dedicated chip.

 

[kingoddball]

Look at the age of the posts you linked.
There have been revisions on the board since then.

I think you are right. I do remember that there was a discussion about this before. I think I can see L2/R2 have resistors tho.
That could be what I got mixed with.

 

[Sander Hoksbergen]

you need resistors or the LEDs will burn themselves out; current limit on available solder pads might not be enough for more than one and/or high-brightness LEDs; pads might not be where you want them; keys aren't transparent

people with hardware details might be able to help you with limitations; use wires for extending; buy a new keypad or modify existing one (exacto knife?)

Doesn't the board run at 3.8v(or 4v'ish)?

An LED can run fine at 3-4v and won't burn out very fast.
You can chain more than one LED off 3v.

Resisters are a good idea, but should not be nessessary... Besides, If I remember correctly, there are already resistors ON the board for these LED pads.

You can power a LED without a resistor but the only reason it's *not blowing up* is due to an internal current limit. And I'd like to remind that I will shoot the first person to suggest putting the LEDs parallel on a single resistor. One fault in any of the LEDs or wires will cause the current to distribute unevenly, resulting in only one LED working at a time.

 

[quantenmagier]

You can power a LED without a resistor but the only reason it's *not blowing up* is due to an internal current limit. And I'd like to remind that I will shoot the first person to suggest putting the LEDs parallel on a single resistor. One fault in any of the LEDs or wires will cause the current to distribute unevenly, resulting in only one LED working at a time.

I dont really see an alternative on putting them in parallel, also cant believe the current will distribute 'unevenly', wont this only happen if they dont really reach the Threshold-Voltage?
If you put them in an row you wont get the voltage needed, do you?
For not using a Resistor i would recommend putting 3 LEDs in an row and all these short 3-LED-Circuits in parallel

Should be fine if the pad had 5V you get a third so about 1.667V for every LED, current will be automatically correct, if voltage is right:

    /--L---L---L---\
-5V |              |
 >--+--L---L---L---+--> +5V
    |              |
    +--L---L---L---+
    |              |
    +--L---L---L---+
    |              |
    +--L---L---L---+
    |              |
    +--L---L---L---+
    |              |
    \--L---L---L---/

just my three cents
QM

 

[paulguy]

I think he meant to not put them in parallel all using 1 resistor, because if one of them fuses and becomes 0 resistance and no voltage drop, you'll get a kind of short, or something, and all of them will stop working.

Been a while since I messed with any of this stuff, so I'm likely off the mark as to the REASON, but from most designs I've seen, each LED has had their own resistor.

 

[DaMummy]

cant we just agree that the pandora lcd screen will provide enough light to clearly see the keyboard and be done with this conversation?

 

[parag0n]

cant we just agree that the pandora lcd screen will provide enough light to clearly see the keyboard and be done with this conversation?

No, because it doesnt.

The suggested use of the pandora is with the screen locked in place, but at the angle it locks, the light is all shining in your face.

If you try and use it with the screen half-way, so you can see the keyboard, it moves backward as you type / use the touchscreen.

 

[Masterfurbix]

Just a stopblock would be able to fix that, a little piece of wood or plastic to contact the hinge. I plan on doing it to mine, I like having a tilted screen

 

[Sander Hoksbergen]

I think he meant to not put them in parallel all using 1 resistor, because if one of them fuses and becomes 0 resistance and no voltage drop, you'll get a kind of short, or something, and all of them will stop working.

Been a while since I messed with any of this stuff, so I'm likely off the mark as to the REASON, but from most designs I've seen, each LED has had their own resistor.

You're getting there but not quite.

LEDs are diodes and thus have a very steep resistance decrease at their forward threshold. Not a single LED, not even the ones in the same batch, will have the exact same forward threshold, there is always a margin of error. What this means is that the equivalent resistance for each LED is not the same at your operating voltage. This results in bright LEDs for those that have a lower threshold, and dimmer LEDs for those that have a higher threshold.

If you mix LEDs from seperate batches or different colors(!!!)(which have completely different thresholds) this will often result in just one LED sinking all the current.

So yeah, never put LEDs in parallel, in series with just one resistor. It's not going to short (that's what the resistor is for), but it won't look nice...

 

[paulguy]

Ah thanks. I was thinking something like that but was having trouble expressing it in words and just figured it was nonsense.

 

[Mqark]

cant we just agree that the pandora lcd screen will provide enough light to clearly see the keyboard and be done with this conversation?

No, because it doesnt.

The suggested use of the pandora is with the screen locked in place, but at the angle it locks, the light is all shining in your face.

If you try and use it with the screen half-way, so you can see the keyboard, it moves backward as you type / use the touchscreen.

I agree, I was attempting to type with the Pandora in bed last night in the dark and the light the screen casts is sufficient to read, but only if the screen is angled down to cast the light onto the keys, and at that angle, you can't see what you're typing. A lit keypad may be a nice effect, but is also a necessity for this kind of purpose so I'll be following this thread keenly for developments on nice solutions to the problem.