The optical guitar pickup.

[moeburn]

The LDR, although a tiny puny magnetic field, is a magnetic field.  Works just the same as an electret microphone.

I don't see where you got a magnetic field with a LDR :?:

Regards,
tomboy

Nevermind, I was completely wrong.  The LDR isn't producing any current, my amp has a bias in it.  I didn't know it did.

[Eric H]

There was something like this advertised in Guitar Player Mag IIRC, was a light sensor/light pickup with a sizable structure just in front of the bridge over the strings. It stated 'works with any type strings even nylon strings'...

I remember several, Pete -- NAMM annoncements, too. I can't remember any test reports, though. BTW this was probably 20 years ago (I haven't read too many guitar mags since the mid-late 80's)

-Eric

[Narcosynthesis]

having a quick look at the lightwave system, they use infra red light, which seems like a better idea than a normal led, as with normal light, you are almost always going to get extraneous light influencing the pickup, ie a slightly different output/sound between a well lit room and a dingy bar, using infra red leds and ldrs would hopefully solve that

David

Either way, its in an enclosed case, so light interference won't be a problem at all.  But there is near IR and far IR pollution everywhere anyway.  I think they used IR LEDs because they are much more efficient and wear out batteries slower, which is a good idea.  At least, I think they're more efficient.  My only IR exploded when i hooked it up without a resistor.

wouldnt it be fairly hard to have a fully enclosed box for it, considering you need to let the strings vibrate without fouling on the box...

David

[corbs]

what do optical mice use for motion detection? they have a fairly fast responce time.

[casey]

still, the palm muting question still arises in my mind...how do you get around something like that ?  would it be picky on what you could do with it ?  palm muting a guitar is used for more than just heavy metal...

[corbs]

still, the palm muting question still arises in my mind...how do you get around something like that ?  would it be picky on what you could do with it ?  palm muting a guitar is used for more than just heavy metal...

the muted sound is just one of the string vibrations being damped in a certain way normap puckups manage it fine...

although i don't think moeburn or anyone else thats interested is really looking for something that would be exactly the same - what would be the point

[moeburn]

wouldnt it be fairly hard to have a fully enclosed box for it, considering you need to let the strings vibrate without fouling on the box...

David

Right, so the enclosed box absolutely must be at the  bridge where there is the least amount of lateral vibration.  Which introduces the problem that you can't rest your palm there to mute.

However, you could design the box so that it is on springs and has a 'palm' of its own to mute the strings.

[Jule553648]

Sorry for opening extremly old topic.

But I am wondering if that optical pickup ever worked?

I am also about to try making it for fun.

[jimbeaux]

The "Photon Midi-Converter" used an hexaphonic infrared pickup. It had 6 infrared LED / phototransistor pairs to isolate each string's output.

(Seems I remember that you could use "tap" the optical pickup output - but I'm not 100% sure)

http://www.youtube.com/watch?v=E8n2jT2QbAM

http://www.keyboardmuseum.com/ar/k/kmuse/photon.html

[Gurner]

having a quick look at the lightwave system, they use infra red light, which seems like a better idea than a normal led, as with normal light, you are almost always going to get extraneous light influencing the pickup, ie a slightly different output/sound between a well lit room and a dingy bar, using infra red leds and ldrs would hopefully solve that

David

Even using infrared....you're still gonna get extraneous light affecting the pickup - the way to avoid extraneous influence is to amplitude modulate the signal fed to the infra red led....then demodulate the signal as rx'ed from your pickup sensor.

[askwho69]

any schematic on this ?

[Jule553648]

I would like to know which sensor is better.

LDR, photodiode, phototransistor, optical mouse sensor?

[jasperoosthoek]

Taken from: http://www.lightwave-systems.com/products/guitar_selection.php and http://www.youtube.com/watch?v=z_hls5mBHzc

It works and there is a market for it .

[Gurner]

Some obvious concerns ...16 hours battery ...p1ss poor!

No battery = no sound (out of the jack socket at least!)

They've put the sensor in the bridge presumably because  in that position, the light can be 'concentrated' exactly below the strings without much divergance (ie when string bending)...which means less lights needed (else otherwise you'd need lights in the 'voids' between the strings... but more lights = more battery drain...& IMHO the battery life is already p1ss poor!), but such pickup positioning is going to give you a very 'bridgey-esge' sound' (full of jangleyesque harmonics)...I'd have thought an acoustic guitar would sound  fuller/richer if the strings were sensed nearer the neck.

[moeburn]

Wow what an old topic.  I just got an email in my inbox saying someone had replied to it.  I haven't been making my own guitar products for years. 

For the record, I gave up on trying to make this as soon as I discovered that someone else had already produced and marketed the idea.  Given that I was only 17, working with parts I could buy from the local surplus store, and that I was competing with a large company with multiple staff and experience and money, I gave up.  My only motivations were that I thought I was the first to think of this idea, and that I quickly got a result that sounded so much better than a regular electric guitar.   

Good luck to anyone who goes further with this idea, the sound that it produces, even with the most basic 5-part circuit like mine, is phenomenal.

[jcgss77]

No!!!!! Don't give up!!!

That is a reason to keep up with developing your idea, even if someone else has already thought it up!!!  You have the ability to think outside the box!  I think we all know what happens to commercially produced items, they make sacrifices and overcomplicate things (of course, for a reason) which can be made simple here and developed by a team which spans the whole globe, and for the love of it, not for the financial gain!  I think this idea is pretty awesome.

[Taylor]

Indeed, this is a great idea, and if it's simple as you make it out to be, would have lots of interesting uses for DIY. Perhaps you can't make a million bucks from it now, but I know people would be interested to know more. Selling kits would be cool.

I don't exactly get how it works. How does a varying resistance create an audio signal by itself?

[Eric H]

Indeed, this is a great idea, and if it's simple as you make it out to be, would have lots of interesting uses for DIY. Perhaps you can't make a million bucks from it now, but I know people would be interested to know more. Selling kits would be cool.

I don't exactly get how it works. How does a varying resistance create an audio signal by itself?

After briefly scanning the thread, you can call me mystified, as well. ;-)

[Taylor]

Oh, and as RG notes on the first page, I don't think any normal LDR will respond at guitar fundamental frequencies... that can't have been a regular LDR can it?

[PRR]

> How does a varying resistance create an audio signal by itself?

moeburn later said "my amp has a bias in it". If an input grid, base, capacitor is leaking DC, a photoresistor will modulate the DC into a voltage.

I too have doubts about photoresistor speed; but we can get many volts out of an LDR in a fraction of a second, so we can get a teensy part of a volt at audio. And moeburn did say he needed heaps of gain.