anyone here a licensed electrician or electrical engineer?

I'm a licensed idiot in several states, so I can't offer any advice on this issue...

Peegoo will probably answer your question...

He knows everything...

 

Very cool. What are the dimensions of the neck, how large are those numbers? I assume this guitar is meant to be played, i.e. not just be show piece? I'm also assuming you want the numbers to light up when that fret is fretted? But I might be wrong there. If I am just ignore the "switch" part below, it's just 12V and 0V (ground) "bus"/parallel wiring.
Where exactly where you planning on sticking the LED modules and how were you going to wire them? ... At any rate, if you do want to use a 12V module here then you need to wire the 12V as a bus, and then have the fret wire close the circuit for the specific module. Lemme try and ASCII it somehow:

Code:

12V   -----|-------|-------|
           +       +       +
          LM1     LM2     LM3
           -
           |
          Switch
           /
           |
GND  -------------------------

LM1 ... is your modules. Switch is the contact at the fret. So presumably all the strings are already grounded so you're all set there, you just need to write the negative of the module to your fret. Do you have the physical space to get the module in? If you're really keen, buy one, give it 12V, and see what that looks like. I didn't draw the circuits for the other 2 modules, they're all the same, the + goes to 12V, the - goes to the fret, if the strings are grounded then fretting the string will close the circuit. [Again, ignore all this if I'm wrong about you wanting to connect this to the fretting action, if you're just looking to light those up there's no "switch" in the diagram, you just wire them all in parallel].

Looking at the specs, it says 624 lumens which is almost as bright as a 60W incandescent bulb... which is pretty bright. Another thing to consider is you're going to potentially lose a lot of light inside the neck so having individual LEDs be right behind your numbers would be more efficient. When you say a lot of light I guess I'm not quite sure what you're looking for... A motorcycle/car headlight is about 700 lumens. Are you looking for 11 motorcycles worth of light coming out of the neck? That could be awesome. Also consider more light usually means more heat from each of these modules...

 

No resistors with your modules. They're for use in your car, or boat, or RV. They take 12V.

Resistors are typically used if you're just using LEDs. LEDs have a more or less constant voltage drop and require a certain current to produce a certain amount of light. The resistor in an LED circuit is to drop the "rest" of the voltage. So for example, if you have an LED that has a 2V drop, and you have a 5V supply, and you want to have 25mA, you need to figure out the resistor value that drops 3V with 25mA. V=IR so R=V/I. So in this scenario you'd wire a 120 Ohm resistor in series with the LED and then hook this to 5V. Usually with individual LEDs you would want each LED to have its own resistor. But this is all for discrete LEDs. Modules with extra electronics or LEDs with integrated resistors are different...

 

I actually am both a licensed electrician in the State of Washington and a registered Professional electrical engineer. I haven't gone thru them in detail but Larry's calcs looks reasonable.

 

For very quick try you can solder some wires to the module and touch that to your car battery terminals. That's 12V and your car battery can power this thing with ease. I searched for 12V 50W power supply on Amazon and saw lots of options that actually mostly say they're intended to power LED modules. One of those should work just fine.

You will want to buy the mating socket for your power supply's 12V plug. Then solder wires to it and to all your modules. That socket will presumably end up somewhere on the perimeter of the guitar so you can plug it in and you'll need to figure out exactly how you mount it. There's really no "breadboarding" required here and I don't think you need alligator clips or any USB related items (don't try and power this from your laptop or something). Power supply, socket, soldering iron, solder, wires should be all needed for this project. I am still going to guess you'll end up not wanting to use these modules when you try them out, either too much light or too much heat or both. But give it a try.

Something like this guy for the power supply:
https://www.amazon.com/dp/B06Y64QLBM/?tag=tdpri-20

Another note is it looks like this module is compatible with automotive bulbs like T10. It's meant to be used in the same application as any other automotive bulb with the same connection style, so one side of that PCB edge (i.e. left and right) would be the + and the other would be the - (just imagine it's a car bulb, I'm sure you've plugged them in/replaced them lots of times).

 

I was looking through that Amazon listing again and noticed someone is saying:
"My only complaint is they produce a very high RFI" ... which may mean they have an onboard switching regulator... doesn't really matter why but the implication is it might get noise into your pickup signal. So that's something else to watch out for.

 

If you want a battery then you probably don't need any power supply. You'll just hook up the modules to said battery.
The problem is how big of a battery you'll need. We calculated the current as 2.75A. Batteries are sized by Amp-Hour (and you'll also want to make sure it can continously deliver this current, which btw is also true of your wires, they have to be the right gauge to carry this current, it's not crazy but it's not nothin') which means I can give you 1A for 1 hour. So if you wanna gig for an hour on said batter you'll need a 12V battery that's at least 2.75A-Hr ... Are you OK with throwing away your batteries after each gig or do you want rechargeables? You could make this work with 1.5V alakalines... 8 of those in series will give you close to 12V. They might last you an hour. Are you OK with a small motorcycle size battery on your guitar strap? I think they have some lithium rechargeables for motorcycles that aren't terribly heavy. You could re-charge those with a battery car charger.

https://www.amazon.com/dp/B07X5G2FFW/?tag=tdpri-20

Now if you had individual LEDs and less light you'd be drawing a *lot* less current than what your car headlight size beasts are drawing, so you'd be able to run them for longer of smaller batteries.

p.s. I'm not sure I'd want to walk around with a made in China, re-chargeable lithium battery strapped on my body though. Lithium batteries have been known to catch fire, explode etc. which shouldn't happen during normal use but probably isn't the safest thing in the world. But in terms of giving juice to these modules, it should work.

 

What do you mean 1 fret at a time as I play... you wanna cycle them? That's a lot more complicated. Also potentially more noise for your pickups. All on and all off is easy, just one switch in series with the battery (on the 12V or ground, doesn't matter).

 

My advice would be to build a small test setup. Make a small "fretboard" with say 5 frets. Get some led's with integrated resistors. Get a small battery pack or just use a 9 volt battery and a 9 volt adapter.
Drill a hole between each fret to mount the
LEDs. make the fret slots a little bigger than normal so the frets are held in but easy to pull if needed to get to the wire underneath. (If that is how you are going to make the connections. ) Then start playing around to see what works. As for the type of switch you will need, you can probably use an on / off/ on. But it all depends on how you wire it up.

 

TDPRI folk are a righteous bunch of people. Answers like this are the whole reason that the Web was invented.

 

ok, so you want to do this thing where you write the frets themselves such when they're fretted they turn on a light. so you'll want to wire the fret to the negative side of your 12V LED modules. And then another switch to connect the negative terminal of the battery to the guitar's ground which is what the strings are connecting to through the grounded bridge.

This is getting a little bit towards "sketchy" territory but the current to each single LED module seems to be small enough. The reason this is sketchy is because now your circuit is closing through the fret, the string, the grounded bridge, and then your other switch that enables this mode (the one that's connecting the negative of the battery to this other guitar ground) and all these contacts are a little iffy. The iffiest one being the string to fret contact, the second iffiest being the bridge to string. Nothing terrible is gonna happen though other than it just won't work as the contact resistance will be too high.

I would wire this with two toggle switches. One switch is in series with the battery 0V terminal going to the negative side of your LED modules (I think they can be used in any polarity anyways from what I've seen in the listing). This switch is the regular on off. Then wire the second switch between the battery negative and the guitar's ground. This switch controls the "as I fret" mode. You wouldn't have both on at the same time (that would just be having everything on).

and yes, switches, like anything electrical, are rated, typically for voltage and current. Buy a switch rated way above your 2.75A. That shouldn't be a problem.

I want to add another warning here. Make *sure* you're *never* shorting your battery. I.e. you never have a circuit that directly connects the + to the - of the battery without having an LED module in the way. With the sort of somewhat more complex wiring we're talking about here you have to be careful. A motorcycle battery can provide a *lot* of current, it's used to crank the starter, it can weld your string to your frets for starters. So at the risk of being a party pooper again, consider smaller LEDs, lower voltages and current. I think those lithium batteries tend to have over-current and over-temperature protection (double check that) so at least it won't explode if you short it, that'd be sort of bad.

 

Guy, is it really worth tanking your whole neck because you bought the wrong LEDs? It's a mis-spent $20. Just let it go and buy something that's not so complicated. You messed up, it happens, get off this rollercoaster and buy the mouser LEDs.

 

A lot of your light from this module is going to end up lost inside your neck though since some of those LEDs would be obscured. I wonder if it's possible to desolder them but I'd have to see the board/circuit. Also with any white light source you're automatically losing a lot of brightness because your numbers are coloured so they act as a filter (And they're probably not perfectly transparent either, so there's a loss there). Using a red LED in front of the red numbers would be a lot more efficient. 3 high power red LEDs in front of that red number might end up giving a lot more light for a lot less power than the module.

There are some pretty powerful individual LEDs though you're right you'll need a few per number most likely and it's gonna be a bit of a pain getting them mounted properly and wired. Those chip LEDs are designed to go on a PCB.

Any rate, it feels like you should do a little more experimenting here before you make up your mind. Maybe you can find smaller modules, I don't necessarily think a module is the "wrong" answer here, but this one seems like it's too "hot".

You should check out Ben from Crimson Guitars on YouTube. He build a neck with LED fret dots in it and his work might give you some ideas. He did a fairly clean job of mounting LEDs inside the neck (but then proceeded to "level" the LEDs lens, WTH).

 

So you want the lights to be hot? Are you going to nail the fretboard to the neck? Because any heat source that's strong enough to melt bubbles out of the epoxy is going to melt the glue holding the fretboard on first.

I just think you should take a step back and reassess.