Resistor for LED on LZ trik PCB

[Yuuki]

Hello,

I would like to know what kind of resistors do I need for LED on trik 1.2 pcb and where I can buy some
The LED I have are from Zeal : https://zealpc.net/collections/accessories/products/leds (regular one, not RGB)

Here is a picture around the capslock area 



Best regards

[Tactile]

All of the resistor locations I can see appear to be already populated. Are there no resistors on the other side of the board?

[Yuuki]

No there is nothing.

I assume than the RXXX thingies are the location of the resistors.
The DXXX are diodes and are indeed already soldered.

[quochung1989]

[Tactile]

Ahh... I see now. Those are tinned SMD pads. Okay, carry on...

[Yuuki]

Thanks for the answers !

I have a couple more questions :

1/ Gon sells some resistors on his website and he recommand different Ohm value for different color. Why is that ?
2/  The 806ohm one will work with any LED colors ?


Best regards

[TalkingTree]

Because different colours require different resistors and Google has plenty of knowledge about Ohm's law and resistors for LEDs. This site has a script to do the math.
Correct me if wrong, but are you putting a resistor on the Caps Lock pad to use it as an indicator? If so, make sure your PCB supports that. It looks just a backlighting pad to me.
Also, you might wanna add some solder to your switches' pins. Especially that Left Shift.

[Yuuki]

Because different colours require different resistors and Google has plenty of knowledge about Ohm's law and resistors for LEDs. This site has a script to do the math.
Correct me if wrong, but are you putting a resistor on the Caps Lock pad to use it as an indicator? If so, make sure your PCB supports that. It looks just a backlighting pad to me.
Also, you might wanna add some solder to your switches' pins. Especially that Left Shift.

Thanks for the information.

The L shift works fine But it's true that it seems lacking solder.

I did some research (and also tried to remember some stuff I learned at school long ago...)

So here what I got so far (please correct me if I'm wrong) :

1/ usb 2.0 gives 5V 500mA
2/ according to your link, orangish LED should use between 2 and 3 V
3/ On the Trik pcb I showed, resistors and LED seems to be in series (which is logical)
4/ If i look at the trace on the pcb, it seems that I can put only 1 led (and the corresponding resistor) and the circuit will still be closed ? no need to install ALL LED (which make sense since it supports different layout like wkl, Cherry caps lock) <--- can someone confirm this ?

Now what I don't understand is why Gon recommend different resistance value for different pcb (470 for his pcb and I think kmac pcb and 820 for trik and a87 compatible pcb)
http://www.gonskeyboardworks.com/electric-parts/15-resistorssmd-100-pcs.html
Also, I don't know if the capslock led can be used as an indicator on the TRIK pcb. There is nothing about it on the software part at least. Just the different led "mode". So if anyone knows....

Best regards

[TalkingTree]

resistors and LED seems to be in series [...] can put only 1 led (and the corresponding resistor) and the circuit will still be closed ? no need to install ALL LED

Since they are in series you surely don't need to populate all LEDs, but you do need to solder all the resistors, or the trace will be left open at the first pad.

Now what I don't understand is why Gon recommend different resistance value for different pcb (470 for his pcb and I think kmac pcb and 820 for trik and a87 compatible pcb)

To my understanding, that's because of the voltage drop across all the LEDs which depends on the number or total LEDs. The more LEDs, the more drop, the smaller resistance you need.
Also, the suggested values would allow the usage of LEDs of any colour.

Also, I don't know if the capslock led can be used as an indicator on the TRIK pcb. There is nothing about it on the software part at least. Just the different led "mode". So if anyone knows....

If that's your goal, you should ask the maker before doing any, potentially, useless soldering job. I tend to believe you simply can't, but again, ask someone with better knowledge of that specific PCB.

[Yuuki]

Thanks for all your answers !

I think that each led/resistors pair are parallels to the "main" circuit so I should be able to solder just one pair and test it. Or maybe I read the pcb trace wrong
I will try for the capslock indicator thingy and will report back as soon as I get the 820ohm resistors I ordered.
I will also try to ask LZ about this in the meantime

[TalkingTree]

I think that each led/resistors pair are parallels to the "main" circuit so I should be able to solder just one pair and test it.

Indeed, testing such thing shouldn't be hard or time consuming.

I will try for the capslock indicator thingy and will report back as soon as I get the 820ohm resistors I ordered.

You can try with a higher resistance resistor for the sake of testing. You can scavenge some on dead electronics.

[Yuuki]

So I tried soldering some 820 ohm resistors : ERJ6ENF8200V 820R 1% 0.125W 0805
The LEDs didn't work.
So now I'm wondering if I should solder them all.

The thing is, what about the additional keys like the one for the winkey spacebar like in this picture :



It's weird that I should add resistors and led in place where there isn't even a switch to begin with.

Any help and knowledge is welcomed

[Photoelectric]

Resistor value should be between 400-1500Ohm, or so for best results.  The higher the value, the dimmer your LEDs will be.  I've used 800 and 1200 Ohm resistors on multiple TRiK PCBs.  Personally I usually go for higher resistance because I don't like eye-blinding LEDs, so for the latest TRiK PCB I put together, I used 1200 Ohm resistors, and it came out just right (in my subjective opinion).  Unfortunately using different resistor values for different colors of LEDs usually does not help equalize their brightness, because the intrinsic brightness of LEDs can vary very dramatically from brand to brand and color to color.  For instance "warm white" is usually super bright compared to "purple" or "yellow".  You can just go with a single resistor value for the whole board or use lower value resistors just for the Caps Lock and Scroll Lock indicator keys.

The resistors are soldered over those little solder-covered pads that have "R###" next to them.  So for example "R151" for the Caps Lock resistor. 

This is an example of high quality resistors I'd recommend:
http://www.mouser.com/ProductDetail/Panasonic/ERJ-6ENF8060V/?qs=%2fha2pyFadujRzH3MhLWy8jksxzMR5rENUa7Yjiktq0qEVW3lXotcGg%3d%3d

These are 806 Ohms and should result in fairly bright LEDs.  You can set LED brightness to 100% or 50% in firmware.

P.S.:  Your resistors are fine.   For winkeyless layouts (1.5x modifiers), the LEDs for the right side Alt/menu/Control should be inserted in the reverse polarity orientation!!!  This might be why you don't see one of those LEDs light up.  I don't see any resistors installed on the PCB in your last photograph.

[Yuuki]

Thanks

I soldered the capslock and escape resistors/led but to no avail. Do I need to solder them all ?

The resistors I used are 2012 size, 820 ohm smd so I think they should work.

[Photoelectric]

Yeah your resistors are good.  You don't need to solder all the resistors first.  Make sure you are inserting the LEDs in the correct orientation.  If you don't, they can be damaged permanently and will need to be replaced.  + (long leg) into the + hole, - into the -.  Make sure there's contact between the metal parts when you test-insert your LED.  Are you testing the Caps Lock LED?  Esc might be off completely if LED mode is off on the keyboard.  I think the default combination to toggle LEDs on or off is Scroll Lock pressed together with "1".

Also, SMD parts are delicate--you can damage the resistors with enough heat from the soldering iron.  You should use much lower soldering temperature to attach them to the PCB.  It's a pretty delicate procedure.  If you have a multimeter, you can test the resistance of each resistor after you solder it on, for consistency.  If a resistor is damaged, LED won't turn on.

[Yuuki]

All right thanks for everything !

Im pretty sure I didn't mess the polarity. But maybe I did damaged the resistors. I will try again and report (my success).

Oh and the default macro for changing LED mod is pause + 1-5 for a TKL I believe. (pause is the default "M" key in triker)

thanks again

[TalkingTree]

So now I'm wondering if I should solder them all.

I believe so.

The thing is, what about the additional keys like the one for the winkey spacebar like in this picture :


It's weird that I should add resistors and led in place where there isn't even a switch to begin with.

It is not. Universal layouts have the same key in different position but their existance in the matrix is given by the diode. 6.25u and 7u spacebar switches share the same diode because they are mutually excludent. You can't use both at the same time.

[Photoelectric]

Here's a great budget multimeter:  https://www.amazon.com/Extech-645618-Digital-Mini-MultiMeter/dp/B0012VWR20   It's a helpful tool to have when putting together or modding PCBs.  You can diagnose a lot of issues with a multimeter, testing resistance and continuity.

I don't know what kind of solder you use (hopefully Kester 44), but for SMD parts you can use something like 600F and a thin tip iron.  Use some flux on the pads before you put the resistor on them prior to soldering (and have great ventilation!!)  I usually hold a resistor down with a tool in my left hand and then press down a skinny edge of the soldering iron tip into the perpendicular gap between the pad and one side of the resistor and wiggle lightly.  Flux helps a lot.  Then the same on the other side, while pressing down on the middle of the resistor.  It's still a slow and annoying job without a hot air station.

[digi]

Here's a great budget multimeter:  https://www.amazon.com/Extech-645618-Digital-Mini-MultiMeter/dp/B0012VWR20   It's a helpful tool to have when putting together or modding PCBs.  You can diagnose a lot of issues with a multimeter, testing resistance and continuity.

I don't know what kind of solder you use (hopefully Kester 44), but for SMD parts you can use something like 600F and a thin tip iron.  Use some flux on the pads before you put the resistor on them prior to soldering (and have great ventilation!!)  I usually hold a resistor down with a tool in my left hand and then press down a skinny edge of the soldering iron tip into the perpendicular gap between the pad and one side of the resistor and wiggle lightly.  Flux helps a lot.  Then the same on the other side, while pressing down on the middle of the resistor.  It's still a slow and annoying job without a hot air station.

Kester44 is flux cored, no need for extra flux. Just heat up some of the solder on one of the two pads then grab a resistor or diode with your tweezers, quickly heat the solder on the pad and slide into place.

Good demonstration video

[Photoelectric]

I've found that it's much cleaner to just add flux on top of the existing solder on those pads for the TRiK PCBs.  You can certainly add extra solder, which will be functional if not "pretty".  It's also easy to add too much solder, as the distance between the two parts of the tiny resistor is quite small, and aligning and holding down a resistor over rounded bulgy (and slippery) extra solder dollops is more difficult.

By the way, that video is for a diode, which is larger and easier to deal with.

[digi]

I've found that it's much cleaner to just add flux on top of the existing solder on those pads for the TRiK PCBs.  You can certainly add extra solder, which will be functional if not "pretty".  It's also easy to add too much solder, as the distance between the two parts of the tiny resistor is quite small, and aligning a resistor over rounded bulgy extra solder dollops is more difficult.

By the way, that video is for a diode, which is larger and easier to deal with.

I have an Edsyn soldering iron with a fine tip.. It's not messy at all if you have the right tools!

Here is a Leeku I did, resistors and diodes.

In the picture you can see the size difference between SMD diodes and resistors. Both very small. I used the same method posted in my video below and it worked perfectly. Different ways to do the same job!

[Photoelectric]

 

[Yuuki]

Thanks to everyone, it now works
I was just a matter of solder (the solder on the pad wasn't enough)
Funny thing, I always switch capslock and control, but you can't do the same for the corresponding led. So when I push the capslock key, the control led lights up.