Wiring assistance


Hello TechTalk

I got a strange situation and was hoping some of you wiring experts could chime in and give me a clue.

Long story short, a while back I bought a ‘DIY LED drop-in’ solution, no soldering required. This was way before the time of ArcEyes or KNserts, so it’s essentially a rat’s nest of wires with small LEDs all wired up.

I’ve never delved into LED wiring ever, or any mod/setup that required extra external voltage such as optical sticks, P360s, flash, etc. so please excuse my noobness.

The person I bought them from is long gone and I am unable to contact them. I didn’t bother getting around to installing it until recently, and here’s where I’m stuck.

I’m planning to wire this to a simple MC Cthulu board, but I’m not sure which terminals to screw these three wires to:

One black wire labeled: (-5v) 0 volts
One blue wire labeled: PCB Ground
One red wire labeled: +5 Volts


Other side of the labels:


Hopefully someone can point me in the right direction. I’m not even sure that all 3 wires need to be attached to a screw terminal position at all. My soldering skills are -extremely- limited, so a solderless solution would be best.

Again, the board I’m using is a simple MC Cthulu.

Thanks in advance!


0V IS Ground. I don’t know why there are two. Maybe because “PCB Ground” is to go to the signal wire. That’s all I can think. Regardless, before I tried connecting a bunch of things, I’d try just connecting the 5V and the 0V.

I’d grab two eurostyle terminals and wire each one up like this:

Just connect ground OR 5V to one end of each, and then use a bit of wire to connect the terminals that are next to each other on the other side. Then take one wire, and connect it to either a GND screw terminal for 0V or the VCC terminal for 5V.

If the LEDs are off after you wire it up like that, then I would try connecting PCB ground to any of the signal wires (1P, 2P, 3K, etc). Then when you press that button down, it will also be ground, and will hopefully light them up. Or just connect all of the PCB Ground wires to ground if you want them always on. Just stuff them into your ground terminal strip, and they should always be on.


Thanks for the explanation. Still sorta confused, but I doubt that ‘PCB ground’ goes to the signal wires because it came with a set of ground wires with QDs on them, all daisy-chained for each button/LED.

Just to be clear, the VCC port on the Cthulu is for the power source generally right? In this case, the red 5V wire?

Thanks Nerrage!!<33


Still having trouble with the setup, but I looked through some old message logs and the seller provided this youtube video:

YouTube - gig4d’s Channel

It explains a lot, but where I get stuck is at 0:21

It says ‘The +5v and 0v to your PCB’ and they assume I am using a madcatz.

Because I’m using a pre-assembled Cthulhu and I need to connect the 5v to the RED-V USB terminal and the 0v to the BLK-G USB terminal, is there anyway I can tap into these without soldering?

And if I need to solder, what’s the best way to do it? The USB socket plug is already soldered to the board.


VCC is 5 Volts, yes. Just put it onto the VCC screw terminal. No need to solder.


Thanks again Nerrage. I kinda got most of it figured out now, turns out that you were right: the 5V goes into the VCC and the ground ones can both be connected to ground. But when the 5V line connects via either VCC screw terminal location, or the tight row of connections at the top at VCC, the lights glow REALLY dim.

I tried connecting the wire directly to the USB jack area, under the Red-V connection point directly and it glows a really nice, full bright light. How do I maximize the brightness, and where should I make the connection to ensure that I get the bright light?

I posted in the Cthulhu thread as well, but it seems to be a bit dead atm:


Did you connect all or one of your lights to the red V? Because what it sounds like is that you may be wired in series, causing all of the lights to be dim, instead of parallel, which may have caused one light to be as bright as if they had all been in parallel.

Also, try connecting to “V” of the top rows. That is voltage. A is simply a data I/O line, so it shouldn’t brighten ver much.

You should be able to solder onto it fine, especially if you’re not using the USB jack. And you can probably get away with just soldering it directly to the USB point using the existing solder. A little more would help if you had it on hand, of course.


I only connected one light for each test, and the lights are wired in parallel, that I’m sure of.

I’ve tried connecting to V of the top rows, and that doesn’t light them up.

Looks like my only alternative here is to solder to the underside of the board, opposite of the USB jack because the USB jack is already installed on the board. Just to be clear, this wouldn’t cause any complications would it?


Do you have a multimeter? Test the voltage across each of the voltage sources and ground and test the current going from voltage source through LED through meter through ground.

My first guess is that the VCC points might be behind a diode which is lower your voltage or might be behind a resistor reducing your current.

Edit: Also, you’ll want to check what safe driving currents are for your LED and not exceed them too greatly lest you risk premature failure.


No, it would be fine. The USB jack is probably not doing anything anyways. I know people to take them off, it will be fine.