# Leds In Fingerboard...

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Hi all,

Doing some research into the idea of having LEDs in a fingerboard.

I came across this very useful page, in which the builder mentions that he used an LED driver. I've never heard of that before, can anyone help me source something suitable?

Here's one I found - is it suitable??

Also, I've found this kit, which doesn't mention a driver.

Is the driver necessary?? Do I need resistors too? Power-wise I could use any type of battery since I'll be making the body.

I just don't really understand the electronics of it, and I don't really want to either. I'm hoping someone can just point me to the correct driver. A little cheeky, I know!

There's also a topic on here already from a while back - http://projectguitar.ibforums.com/index.ph...09&hl=fiber

Thanks,

DJ

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In the effects pedal work I've done, normally to power a LED, I connect the 9V+ from the battery, then use a resistor to take the voltage down to 1.3V-1.8Vish. Different LEDs have slightly different voltage and current requirements, and you can adjust the brightness by the amount of voltage applied to them. I've never worked with several LED's in a row, but if you only want to use one resistor, then the LED's will have to be wired in a series. Here's a site that has a lot of info. Also, try Googling "LED resistor calculator", since there are a lot of sites that do just that. Also, I don't know why you would need a driver.

Hope this helps.

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Ohm's Law: R=V/I

If you have a 9v supply for example, first find out what the forward threshold of the LED is - usually around 0.7v - and subtract this from your voltage, say 8.3v.

Check the recommended current and maximum current values for the LED also. Say for the sake example, 4mA.

So your resistor would need to be (8.3/0.004)kΩ, or 2.075kΩ. This would be 2kΩ in the E24 series, or 2.2kΩ in E12.

If you're running LEDs in parallel then just do this for each LED. You can't really run them in series on the basis that each LED will drop 0.7v, reducing each units brightness down the chain :-\

Those drivers are meant to supply a steady regulated umm...supply for Luxeons from either an AC or DC source, which you don't need in a fretboard unless you want to illuminate your audience or have a warm neck :-D

Just opt for simple low current high efficiency LEDs, which are cheap cheap cheap. You should be able to sand the top flat as long as you don't get near the diode internals.

Probably.

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Oooh, I know, you could make the LEDs light up blimp inlays, then you could have LED Zepplins! :

-Stormy

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Ohm's Law: R=V/I

If you have a 9v supply for example, first find out what the forward threshold of the LED is - usually around 0.7v - and subtract this from your voltage, say 8.3v.

Check the recommended current and maximum current values for the LED also. Say for the sake example, 4mA.

So your resistor would need to be (8.3/0.004)kΩ, or 2.075kΩ. This would be 2kΩ in the E24 series, or 2.2kΩ in E12.

If you're running LEDs in parallel then just do this for each LED. You can't really run them in series on the basis that each LED will drop 0.7v, reducing each units brightness down the chain :-\

Those drivers are meant to supply a steady regulated umm...supply for Luxeons from either an AC or DC source, which you don't need in a fretboard unless you want to illuminate your audience or have a warm neck :-D

Just opt for simple low current high efficiency LEDs, which are cheap cheap cheap. You should be able to sand the top flat as long as you don't get near the diode internals.

Probably.

Excellent, thank you!

Have now given up on the idea of using a driver.

Right, I have some LEDs that I'm thinking of using for this. From the spec I got with them, the forward voltage is 4.5V (they're blue, which I know need a higher voltage). So, if I use a 9v battery, 9-4.5=4.5. The next bit confuses me slightly. You mention "recommended current and maximum current values" - well, I have "Max continuous Forward Current = 30mA" and "Max Peak Forward Current = 75mA" on my specs; are these the equivalent values? If so, do I use 30mA, 75mA, or an average?? OK let's assume it's 75mA (just to finish my example and to check if I understand the theory! Bear with me!) So......

R=V/I

V is 4.5, and I is 0.075, so 4.5/0.075=60. Therefore I need a resisitor value of (60/1000) 0.06 kiloohms, or 60 ohms...yes?

Or, if it was 30mA...

4.5/0.03=150, so a resistor value of (150/1000) 0.15 kiloohms, or 150 ohms???

more

( )

I have some 510 ohm resistors lying around, but that's no use is it? I need somewhere between 60 and 150 ohms.

DJ

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The LED in question should be ran at 30mA ideally I guess. I didn't realise blue LEDs had such a massive voltage drop (conduction threshold)!!

Other than that, the working is sound.

You've seen this then at some point, I take it?

Edited by Prostheta
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Ah, thanks!

The LEDs I have were ones I bought on eBay last year, I got 20 for about the same price as one from Maplin! And some free resistors....

I'm gonna have to do some experimentation now with LED placement and fibre optic cable etc, see what works!

DJ

Hope that helps.

Ciao,

Garth

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Thanks Garth, that really does help!

OK, I went to that page and entered the following figures:

source voltage = 9v

diode forward voltage = 0.7v

diode forward current = 4mA

number of leds in array = 10

hit the button to let the wizard design the array, brilliant!

So, one question: if I make it exactly as it shows, will I get even brightness across all ten? Or will I get the brightness drop that prostheta mentioned earlier?

Thanks,

DJ

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Yeah, that's what I was thinking....I might be mistaken, but surely the forward voltage of each LED will reduce the voltage to each LED in turn? I can see it working if you have a common cathode (all cathode ends tied to one drop resistor) but series?! Hmmm. I'd like a second opinion please doctor.

<edit>

Edited by Prostheta
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You're welcome DJ.

I did mine with bi-coloured LEDs (red and green), and put a resistor on each of the positive leads. With a resistor on each lead, the power being supplied to each of the LEDs is the same.

I chose to go this route instead of using one resistor, so that, if one LED should fail, they all don't go out (remember the old Christmas lights where if one bulb failed the whole string went out?)

I haven't found any difference in brightness between each of them.

You do have to make sure that all of the LEDs are the exactly same. Once, I substituted a couple from a different batch, and you could really see the differences in colour densities when used in "orange" mode. "Orange" mode is created by lighting up both the red and the green at the same time.

Here's a link to a page where I documented my trials and errors:

As far as fibre optics for the side dots, I use plastic fibres out of an old Halloween decoration, running from each LED:

The advantage to using plastic fibres is that you can bend them (they won't break) and a little heat will melt the ends into nice little "mushrooms" acting as lenses, magnifying the light.

Hope this helps.

Ciao,

Garth

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Yeah, that's what I was thinking....I might be mistaken, but surely the forward voltage of each LED will reduce the voltage to each LED in turn? I can see it working if you have a common cathode (all cathode ends tied to one drop resistor) but series?! Hmmm. I'd like a second opinion please doctor.

<edit>

I read through that link, but it just doesn't seem right. All of the parallel work is correct, but the series seems like you should see a voltage drop after each LED. But his math doesn't show it, and he doesn't really explain anything on the voltage drop.

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Yeah, I'm really thinking that parallel is the way to go with this anyway now.

Thanks,

DJ

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Yeah, I'm really thinking that parallel is the way to go with this anyway now.

Thanks,

DJ

I think it is better to use as many in series as you can, because you waste less power in the resistors, less overall current. If you want 10 overall, and say they drop 1.5V each, you might find 5 in series with one resistor works with 9V, then have two such series in parallel to make 10.

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Yeah, I'm really thinking that parallel is the way to go with this anyway now.

Thanks,

DJ

I think it is better to use as many in series as you can, because you waste less power in the resistors, less overall current. If you want 10 overall, and say they drop 1.5V each, you might find 5 in series with one resistor works with 9V, then have two such series in parallel to make 10.

Thanks. Hmm, that's interesting. When I put in some values into this wizard, that is exactly what it suggests doing: 2 strips in series linked in parallel to make an array of ten.

Like so:

Right, enough pontification, I've ordered some LEDs and some resisitors and I'm just gonna physically try it a few ways and see what works best!

DJ

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I work with these types of LED circuits all the time at my employer and have a decent amount of knowledge regarding led circuits.

I think that your 2 strings of 5 setup looks good. I have a couple of ideas to add.

I think what you will find is you will probably not get much brightness benefit from running them at their full rated 30mA. Percieved brightness vs current is analogous to lagarithmic curve of a volume pot. Once they are bright, for a large current gain, there will be little brightness gain. While this is only somewhat pronounced if you look at the datasheets, the perceived effect will be much more evident. Consider this when you design for battery life.

Also, you may be doing yourself a favor to consider sucvh things as an external master brightness pot for on-the-fly control and a zener regulator so that peak brightness does not as noticeably change with battery wear.

A totally AWESOME feature (and easy to implement) would be an op amp tapping the pickup signal to make the LED's turn on and off with the attack of the player. If interested, I'd be willing to help with a design/schematic.

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Great information Donovan - especially the practicality of a brightness control. If guess if tri-colour LEDs were used, it would be feasible to have a pair of stacked colour blend pots....!

As an aside, my minor project at college was a multi-band spectrum analyser just a step up from the pickup/op-amp idea. I made several bandpass filtered/half-wave regulated/DC smoothed signals drive an array of bi-colour LEDs with a green "bar" and a red "peak", which was pretty cool and taught be the huge difference in linear representation of logarithmic values right there and then since I didn't do so in class much....absolutely enormous on breadboard, and somewhat difficult to cram into a guitar control cavity however....!

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Great information Donovan - especially the practicality of a brightness control. If guess if tri-colour LEDs were used, it would be feasible to have a pair of stacked colour blend pots....!

As an aside, my minor project at college was a multi-band spectrum analyser just a step up from the pickup/op-amp idea. I made several bandpass filtered/half-wave regulated/DC smoothed signals drive an array of bi-colour LEDs with a green "bar" and a red "peak", which was pretty cool and taught be the huge difference in linear representation of logarithmic values right there and then since I didn't do so in class much....absolutely enormous on breadboard, and somewhat difficult to cram into a guitar control cavity however....!

Thx Prostheta. My company is keen on training and part of my position there allows me to explore electronics during my downtime. It is a lot of fun as well as at times frustrating and perplexing.

It sounds like your college project was very similar. Opamps have a huge place in the scientific instrumenation world due to their ability to listen and magnify without affecting what their listening to.

I've not had a chance to mess with any tricolor LED's. I have played with the bi-directional, bi-color types, those are interesting, but your comment opens up even more opportunity for our friend djhollowman. It would increase the circuit by one set of wires per color, and add one selector switch, but... you could set it up to select the color of choice for mood. They type I just checkout out online just a second ago are four leaded, having an anode for each color and a common cathode. Is this what you meant or are the you you mentioned something else? I can see how multiple pots would handle color blend... and so let's consider takking it now WAY over the top for more "fun with bling".

Imagine this...

Opamp taps pickup signal and amplifies it to useable level to drive LED strings.

Amplified signal is split into 2 branches.

Branch 1 controls momentary on-off, giving the "varying brightness with attack"effect.

Branch 2 controls a series of JFETs in Ohmic mode (voltage controlled resistance), giving a "varying color with attack" effect.

Rotary switch controlling master brightness or mode control. Modes might include steady on, "attack" mode, a random (555 timer setup) blink mode... whatever can be imagined.

Your stacked "color blend" pots controlling color mix and/or 555 timer's drequency/duty cycle.

The point is that the limits are only what you can imagine. I'd love to try this, only my woodworking skills are sucka\$\$.

DJ... something tells me this is not the time for the KISS rule.... but rather a perfect opportunity to make something that is kind of a "been there, done that" novelty into a totally unique as can be, stage light-show machine!

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Wow, this has really set you thinking Donovan!

I really like the idea of a master brightness control pot, or even a tiny trim pot which could be kept inside the control cavity.

Perhaps for this project I'll stick to something fairly simple - I like the idea of only the 12th fret inlay and side dots being illuminated. By that I mean I probably won't have front inlays other than the 12th fret one. I also feel that many of the LED-equipped guitars I've seen on the 'net so far are waaaay too bright, and look garish as a result! I'm all about subtlety! Besides, I'm having trouble enough getting my head around a simple LED array!

However, I'm waiting on delivery of some LEDs which it may be possible to use as front and side markers! We'll have to see.

In fact, I'm waiting on several items to be delivered (everything has to be mail-order where I live! The internet is a lifeline) which will enable me to start experimenting with arrays and such. I'm sure it's gonna be fun!

Yeah, I've also toyed with the idea of those bi-colour LEDs...hmm. A possibility, certainly.

DJ

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Unfortunately, I never got to play with tri-colour LEDs on the basis that I was broke at college! The bi-colours were quite an expense for me at the time also. I guess this one has to live in theory land only for the time being. :-\

Interestingly, I found that persistence of vision was a problem as the green "analysis" dimmed noticeably below the red peak (which got pushed higher by the slightest peak rather than an average - simplicity) with them turning on and off at high clock rates. Just having an adjustable clock rate from ~4Hz to ~2000Hz was just....well, you know what it's like when you make a fantastic contraption....!

My major project was a clock and calendar. 12/24hr, dates and leap years. All TTL just so I could make many massive truth tables in Excel. Solid core interconnect wire bent at 90° angles with pliers and laid flush to the breadboards with little humps and jumps if they crossed. That was my HAL 9000.

That and college would pay for standard parts like 74xx and 4000 chips. NANDtastic. This had nothing on my behemoth of digital law and order.

Edited by Prostheta
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I looked up the pic you posted, prostheta, just out of curiosity, to see what it's for - it's "A 4-bit, 2 register, six assembly language instruction computer made entirely of 74-series chips." So now I know.

DJ

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Not too much of a step down from a Zilog Z80 then really. I cut my teeth programming on my +2A (and Romantic Robot Multiface 128) in assembly.

That chip - incidentally - was commercially released on the day I was born \m/

I am so 8-bit and 80s it's unreal.

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I also feel that many of the LED-equipped guitars I've seen on the 'net so far are waaaay too bright, and look garish as a result! I'm all about subtlety!

I get over-excited sometimes... eyes will be waiting to see what you come up with.

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I have done 5 or 6 guitars with leds.

I usually make it simple. one 9v, directly wired to the leds. no resitors or drivers or anything.

battery life = I have not drained one down yet.

I can get away with out resistors I believe, because I usually run min of 9-10 leds.

to dim the leds, you can wire them all up and put one of those resistor between the leds, and the battery, it will cut the brightness down to something you can look directly at and not go blind.

I just did a mega bright white fret board on my acoustic 8 string I am goodfing with. the are really bright. one resistor and they drop down to something I can look at.

I am going to use a switch to change the brightness.

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Bill-

I remember your Ace Frehley top. That came out really nicely. I'd like to see some closeup pics of some of your fretboard stuff. Your pics that I could find are all very small, too small to make out any detail. How do you route the wires? Are they inside the neck? What kind of surgery does that require or is there some spare room inside a guitar neck? (I've never disassembled one). I don't think I could bring myself to going the route of cutting channels along the outside for aesthetics sake.

I agree, you're right, you can run a series string off one resistor. That's not a problem at all. Drivers come in when you want functionality or power conditioning that you don't get from a battery.

This thread has me inspired and kicking around a unique LED idea myself. I started laying out a rough prototype tonight on a breadboard and so far so good, the simplified version works, but I don't want to give away the details until it's done as I don't think it's been done yet and I'm excited to be the first. The downside is it is going to require a lot of routed wood for all the components on the circuit board to fit. The project will have only about 15 LED's, but will take about 30 other through-hole components on a proto PCB to run in different "intelligent" modes.

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