Author Topic: Question: Why don't my newly soldered-in LEDs light up?  (Read 3455 times)

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Offline deadpool

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Question: Why don't my newly soldered-in LEDs light up?
« on: Tue, 25 November 2014, 08:42:27 »
Hey everyone, I have a Plum MX96 keyboard. It came with holes for LEDs. It also came with 6 LEDs already soldered into keys which worked (ESC, CAPS, PRTSC, SCRLK, PAUSE, NUM). It's marketed as a wireless + backlit keyboard (provided that you install LEDs)

I recently soldered all 96 keys with SIP sockets which went fine. But when my LEDs arrived and I tried to install them, they wouldn't light up. The original 5 keys are still lighting up. FN + F7 seems to be the control to turn backlighting on/off. It works sometimes and turns those 5 keys on/off. I've checked polarity (short leg negative), and tried reversing them as well- no luck. I've also tried FN + V (think this is the Choc Mini 2M command to turn lights on/off). I've also tried different LEDs in different sockets.

Can anyone give me some troubleshooting tips? I'm confused why those 5 keys work (I installed SIP sockets in those too), but the rest don't. Maybe I can reset the board to factory condition, or I burned/nicked the PCB somewhere or something? Does the keyboard store memory somehow? I really like the keyboard and would love if the 5 different colored LEDs I ordered would work.

Here's a link to the keyboard/layout: https://geekhack.org/index.php?topic=33288.0
http://i.imgur.com/xHcgfXy.png
http://i00.i.aliimg.com/wsphoto/v1/703229584_5/Plum-MX-96-Mechanical-Keyboard-wireless-Wired-Cherry-Brown-switch-N-key-rollover-Fast-Free-shipping.jpg


TL;DR:
I just installed LEDs in my Plum MX96. Some aren't working. Any ideas why/how to fix?
Already checked:
-Polarity
-Different LEDs in different sockets
-Connecting with cord vs battery power.

Thanks everyone, I really hope I can get them working right.
« Last Edit: Tue, 25 November 2014, 09:23:27 by deadpool »

Offline samwisekoi

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Re: Question: Why don't my newly soldered-in LEDs light up?
« Reply #1 on: Tue, 25 November 2014, 08:53:59 »
Check for power in the LED sockets.

 - Ron | samwisekoi
Sig auto-typed by my GH36 LH keypad.
I like keyboards and case modding.  Everything about a computer should be silent -- except the KEYBOARD!

'85 IBM F-122/Soarer Keyboard |  Leopold FC200 TKL (Browns) + GH36 Keypad (Browns/Greens) | GH-122 (Whites/Greens) with Nuclear Data Green keycaps in a Unicomp case

Offline dorkvader

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Re: Question: Why don't my newly soldered-in LEDs light up?
« Reply #2 on: Tue, 25 November 2014, 13:05:19 »
looking at the picture there's traces that go to the + side of the LED hole but I don't see any resistors.
http://www.aikb.cn/image/plum96.jpg

Here's my theory: they have it half wired up for you.

What I would do is connect a resistor from the - side of the LED socked to gnd (1K is fine, but anything from 600 ohms up should work. Anything lower than that, ask) and see if the LED lights up. I think it will.


Oh and make sure to include a switch so you don't run down your batteries too quick with all the LEDs on.

Offline deadpool

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Re: Question: Why don't my newly soldered-in LEDs light up?
« Reply #3 on: Wed, 03 December 2014, 20:10:38 »
Thank you so much for diagnosing and replying. As you can probably tell from my problem, I don't know much about electronics. I took a bigger picture of my board, and what I think I'm supposed to do. I haven't found a LED DIY/Guide that includes resistor soldering so I'm a little lost. So if I understand this right, I'm supposed to solder 96 individual resistors to the underside of my board? Dang that's gonna be a lot of space & a rat's nest of wiring. And it's these style resistors right? http://www.ebay.com/itm/New-100pcs-1K-1000ohm-1-4W-1-accuracy-Metal-Film-Resistors-/231031218129?pt=LH_DefaultDomain_0&hash=item35ca889fd1
Thanks again, I'm happy someone knows what's going on.



Offline dorkvader

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Re: Question: Why don't my newly soldered-in LEDs light up?
« Reply #4 on: Wed, 03 December 2014, 22:27:12 »
ok I did some more looking.

Appears as if the LEDs are wired two in series with eachother.

This means that you will only need half the number of LEDs but the downside is that you can only have LEDs with a Vf of half the supply voltage or less.

So if you want red or orange LEDs it's fine, just wire up LEDs as follows: from 5V line run a wire with resistor to LED pair, Run line from LED pair to GND.

If you want blue or green LEDs you'll need more voltage. Blue LEDsa re like 3.6Vf, so you need to step the voltage up to at least 7.2V, I would recommend 7.5V or 8V depending on what resistors are easy to get.

Unfortunately it seems that some LEDs are wired up as a string of three. I hope you like red LEDs.

So basically,
find an LED pair (+ on one LED wired up to - on another)
wire up a resistor from the + to power
wire up other end to gnd.

note that the "gnd you have marked" is actually an LED power trace. an good thing to use as actual GND is the black wire that goes from the batteries to the screw.

Gonna come up with a wiring diagram thing once I find a mouse and plug it in.

Offline neverused

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Re: Question: Why don't my newly soldered-in LEDs light up?
« Reply #5 on: Wed, 03 December 2014, 22:46:36 »
Looking at the board, I have a sneaking suspicion that since the board is double sided, the LEDs maybe be wired in more than just pairs or triples. My suggestion would be to get a digital multimeter, turn it to the continuity mode and listen for beeps as you connect the - side of one LED to the + of another neighboring LED. Once I can get my laptop out I will try to show you what I mean.

Offline deadpool

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Re: Question: Why don't my newly soldered-in LEDs light up?
« Reply #6 on: Thu, 04 December 2014, 11:41:53 »
Thanks guys, yeah the project's on the backburner. I just drew a ground on the board so it wouldn't be so messsy in that picture and easier to read. All this sounds like gibberish right now lol gotta set a night aside to go over it with the board. If I can supply any more pictures etc. please let me know. Wish there was a DIY for soldering resistors with your LEDs, guess most boards come with them :)

Offline pnd4

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Re: Question: Why don't my newly soldered-in LEDs light up?
« Reply #7 on: Tue, 03 March 2015, 01:03:42 »
Sorry if I'm hijacking the thread but I have the same question.

I got my Plum 96 from Massdrop about a week ago and I wanted to go about adding the LED feature. Problem is I saw no voltage on the few LED solder-points pairs I tried and thus was kinda pissed the marketing line "Just pick your LEDs, solder, and you're good to go" wasn't at all true. Zero-documentation in the box, and none I've come across online either. Even Massdrop ignored my plea to ask the supplier any info regarding the LED placement/orientation/specification/anything?!

So after searching around, seems I feel like this thread is my best bet, seemingly the only one attempting to make this board glow..

Anyway, since OP wasn't able to poke around with his multimeter, I took mine out and documented the continuity, the only thing is that I don't have much experience with creating circuits my soldering experience is limited to repairing solder-joints or splicing wire together. I definitely don't want to solder now. ask questions later, after things get broken so any advice is as to how to get my keyboard lit up is greatly appreciated!

Black = Ground-Ground continuity
Green = Positive-Positive continuity
Blue = GND-to-POS/POS-GND (not sure which way the current flows, diodes confuse me hehe)


« Last Edit: Tue, 03 March 2015, 17:20:12 by pnd4 »