I got a little 10k LDR and a bottle cap. Cut the bottlecap so it was thin enough to fit under my guitar strings. Drilled a hole in it, put the LDR under it, hooked it up to my headphone amp. I positioned the pickup under my string so that the shadow of the string was right on top of the hole (i'm using sunlight at this point).
The sound was absolutely phenomenal, sustain is extremely long, there is no noise whatsoever.
Now that I know it works, I'm gonna design a proper prototype (covered to avoid light pollution, LEDs instead of sunlight).
However, I need some advice. Where should I position this pickup on my guitar? It is going to be covered, don't forget, so it will eliminate a portion of the strings. If its at the bridge, you won't be able to palm mute, at least not very well.
Middle or neck at first but you should be able to get it work well in the bridge if it's covered. This sounds like a very cool idea. I'm interested in how your progress progresses. :D
Quote from: vanhansenMiddle or neck at first but you should be able to get it work well in the bridge if it's covered.
The problem with middle and neck is that the strings like to vibrate alot futher, complicates things. Don't forget this has to
cover the strings, so you can't pick the strings wherever i put it.
Which is why this would work so much better on a bass.
Oh, ok, I see. I thought by "covered" you meant the pickup would be covered but you're talking about covering the strings like on a vintage P-Bass that has the cover over the strings and pickups. Well, what's the diameter of the LDR? If it's no wider than a normal pickup pole piece, it may still pick it up ok. It's worth trying anyway.
Quote from: vanhansenWell, what's the diameter of the LDR? If it's no wider than a normal pickup pole piece, it may still pick it up ok. It's worth trying anyway.
My LDR is the exact same diameter as the pickup pole, but the hole i drilled for it is much smaller, only 1/32". I'll try it.
I belive I read something about this in an article about the NAMM and they placed it close to the bridge.
Regards,
tomboy
Is there a reason you're making an optical pickup, or is it just for the sheer joy of mad science?
Either way, cool idea. Personally, I tend to pick behind the neck pickup, so I'd want it mounted pretty far forward.
Quote from: smashinatorIs there a reason you're making an optical pickup, or is it just for the sheer joy of mad science?
Mad science, of course :D
After a bit more playing around, this is sounding alot easier than I thought it would be. Each string is equally bright and loud with the same single pickup. Every sound you can make comes through just as expected, including scraping the strings, different picking techniques, chiming, etc. Except of course, palm muting.
Since it is getting dark here, I tried using a ceiling light instead of the sunlight. Lots of 60hz noise, and having three bulbs at slightly different angles makes for a pretty cool effect.
Did you perhaps use a phototransistor instead of an LDR?
Most LDRs are too slow to respond to 60Hz changes in light intensity from bulbs, let alone string vibration frequencies. In fact, getting an LDR fast enough for phaser use is some times tough.
I wonder what happens when someone takes your picture with a flash camera?
im not sure i understand how you're getting a signal out to the amp. do you have a signal generator which the LDR controls? if so, hahah - instant tuning changes! weee!
if not, then how? also, this could all happen in a little enclosed box which is smaller than a SC pup but fits around the strings. wouldnt be much of a problem in that respect.
Sorry, but I didn't understood. How a optical pickup will work, if a LDR or a phototransistor can pick only lights, not sounds or vibrations?
Sure it only picks up light which alters the resistance of the LDR. While having a maybe constant voltage applied the current through the device will alter with the frequenzy of the string.
Regards,
tomboy
Michael Faraday (Captain Capacitor) discovered that whenever a magnetic field (pickup magnet) is moved or changed (string induces change in magnet) in a conductor (pickup coil), a current is produced. This is how your guitar strings can actually generate sound without simply being a variable resistor. They generate about 10-200mV.
The LDR, although a tiny puny magnetic field, is a magnetic field. Works just the same as an electret microphone.
Unfortunately, my LDR isn't quite that strong. I had to use my preamp at full volume, my TS at full volume (minus distortion), and my amp at full volume, to get a normal volume of the guitar. This is probably because the difference between shadow and sunlight isn't strong enough.
Once I get it inside a dark enclosure, with a bright LED as the source, it will be much louder. But you will still probably have to have an active guitar with batteries in it.
I just thought of another neat advantage though - nylon guitar strings on an electric. Imagine that!
Optical pickups are already being sold, although only for bass at the moment.
http://www.lightwave-systems.com
-- T. G. --
Quote from: tommy.genesOptical pickups are already being sold, although only for bass at the moment.
http://www.lightwave-systems.com
-- T. G. --
Yeah, thats why I said this would work so much better on a bass :P
But its so much cooler when you get it working before they do.
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
Quote from: Narcosynthesishaving 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.
Quote from: moeburnI just thought of another neat advantage though - nylon guitar strings on an electric. Imagine that!
ooh you might get some cool diffraction weirdness too 8)
Quote from: 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
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'...
Quote from: tomboyQuote from: 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.
Quote from: petemooreThere 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
Quote from: moeburnQuote from: Narcosynthesishaving 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
what do optical mice use for motion detection? they have a fairly fast responce time.
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...
Quote from: caseystill, 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 ;)
Quote from: Narcosynthesiswouldnt 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.
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.
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
Quote from: Narcosynthesis on July 05, 2005, 05:01:01 PM
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.
any schematic on this :D?
I would like to know which sensor is better.
LDR, photodiode, phototransistor, optical mouse sensor?
(http://www.lightwave-systems.com/img/menu_atlantis.png)
Taken from: http://www.lightwave-systems.com/products/guitar_selection.php (http://www.lightwave-systems.com/products/guitar_selection.php) and http://www.youtube.com/watch?v=z_hls5mBHzc (http://www.youtube.com/watch?v=z_hls5mBHzc)
It works and there is a market for it :icon_mrgreen:.
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.
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.
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.
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?
Quote from: Taylor on January 19, 2011, 08:30:02 PM
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. ;-)
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?
> 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.
It sounds like the ideal receptor would be a photodiode or phototransistor, not an LDR, just for the sake of response time. There are high-speed photoconductive components, but the standard LDR is not one of them.
Are there any photodiodes or -transistors where the optical element is exposed? The ones I've seen are always sealed PDIP packages.
Quote from: PRR on January 19, 2011, 09:26:14 PM
> 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.
So for this to work with any amp, I guess you'd need to connect it to something like a transistor preamp with no input cap. Varying the resistance between transistor base and ground does seem to do the trick in simulation.
http://www.creative-science.org.uk/lightbeam.html (http://www.creative-science.org.uk/lightbeam.html)
Quote from: artifus on January 20, 2011, 01:32:14 AM
http://www.creative-science.org.uk/lightbeam.html (http://www.creative-science.org.uk/lightbeam.html)
Crazy! Cool link.
It occurred to me that if you mounted such a "pickup" towards the neck, the light on the sensor would be blocked twice per string oscillation - once going one way, once going the other. So you get an octave up effect. 8)
http://www.youtube.com/watch?v=RheshR-9Q0w
I saw this thing:
http://articles.ircam.fr/textes/Leroy06a/index.pdf
They used reflective sensors - phototransistor and LED in same case and they measured reflections. This could be used more instead of a pickup. But they made things complicated by modulating the whole thing...
Apparently piezo assistance was chosen to accomodate and output the HF pickuping jobs.
Either that is the demonstrationists preferred tone or, and, there didn't seem to be any great variance when the knobs were reset.
2-D imaginative description of what my preconception of what photo-PU behaviour might be/when:
Seems that any slowness in creation of the electron-analog following the string would be most obvious as the string is moving through the center portion of it's excursion when speed its the highest, or when otherwise nearly still except the uber-harmonic shudderings which continue the as the string 'stops' to changing directions.
...to attempt to describe Pho-PU's ability to follow the 3-D motion of an oscillating string.
It is expected that it will sound like itself, considering the sensors placement at almost the end of the string.
To spread these photo sensing points down the string [like >1 mag pickup basses do] requires giving up some favorite places to access the string for picking, or mirrors on the string, reflecting the LED photons back into the light sensor, or LED's in the strings. Perhaps a tiny portion of string over the photo elements, 12-sided chrome polished zone with very strong lights on it, lots of output preamp...might put some cool dynamic-related-misread-anomolies in the output.
Sure looks like a tidy approach to DIYing 1 pickup per string tech.
> I guess you'd need to connect it to something like a transistor preamp with no input cap.
No; just a resistor to a battery.
Hold the LDR in your ambient light, measure resistance, use a similar or somewhat larger fixed resistor. Battery may be 50V-100V before the LDR arcs/sparks, perhaps lower if you work in bright light and run into power dissipation limits. Lower battery makes less signal but is of course safer. 9V should be ample. 1.5V may be enough.
Since you will surely need an amplifier anyway, you can try to combine them; but it's hard enough to bias a transistor without also having a key bias element change with the light. We normally keep the light-sensor circuit simple, then cap-couple to a standard amplifier.
Photo transistors are much faster, often cheaper, readily available.
Photo-diodes are much-much faster (far faster than audio needs) but make less output.
An LED makes a workable photo-diode. Some glass-case signal diodes are moderately light sensitive.
http://en.wikipedia.org/wiki/Demodulation (http://en.wikipedia.org/wiki/Demodulation)