mattell starmaker guitar, with optical pickup system...

[PRR]

https://youtu.be/bkW4CJjthO0

[pinkjimiphoton]

https://youtu.be/bkW4CJjthO0

already in the first post of the thread, bro

[Rob Strand]

its definitely gotta be the right guage string, and its gotta be within the "beam" for it to work. i find if i push on the string just slightly behind the "bridge" i can influence how the tracking will be. there's a definite sweet spot where the guitar almost plays itself.

I guess with such a simple set-up you have to accept some limitations.  It might be possible to use two of those things with a slight vertical offset to make the operating window wider.

There's quite a few "real" optical pickup manufacturers they all use more complex schemes for the sensing simply because the beam-breaker method can only go so far.

i may try and get one of them gizmos to see if it will work. they look almost identical to the ones in the mattell, only dif is they're not enclosed on all sides. but they do have the "pinholes" for the light to shine thru and be picked up.

They will be very similar for sure.    You can always put you own cover over the top of the "fork".   I had a number of those things I pulled from old printers.  I don't know if I still have them.

[iainpunk]

thanks for the compliments on the hub cap!
i learned to play on that thing and played it for 6 years before i picked up a 'real' guitar. being limited by only having 2 strings forced me to learn techniques to make it sound more interesting, like with rhythm and dynamics, things i found most guitarists at the local jam sessions lacking in.

i have a CNY70 UV reflectiveness sensor left over from a line following robot project, it has a UV LED and sensing transistor next to each other facing the same way outwards, not opposing each other like the most optical sensors, due to the odd arrangement, i dont think it will work that great, i even doubt it will produce any sound at all, but its worth a try. i do have a few IR phototransistors somewhere in a box, maybe those can be useful if the CNY70 doesn't work (and id be able to find them).

ow Jimi, is there a stamping on the inside of the plastic denoting the type of plastic used?
i bet its made out of the best tone-plastic out there.

cheers

edit: 2700th post

[Rob Strand]

i have a CNY70 UV reflectiveness sensor left over from a line following robot project, it has a UV LED and sensing transistor next to each other facing the same way outwards, not opposing each other like the most optical sensors, due to the odd arrangement, i dont think it will work that great, i even doubt it will produce any sound at all, but its worth a try. i do have a few IR phototransistors somewhere in a box, maybe those can be useful if the CNY70 doesn't work (and id be able to find them).

These guys use that method.   They have a heap of patents.  Not sure how they hold up since they reflective idea is a known thing.

https://www.kickstarter.com/projects/light4sound/opikthe-optical-guitar-pickup

I worked on a paper card reader project which used reflective sensors with a lens and a well-defined focal point.  They were quite expensive.   I was put on the project right at the end to "make it work".

The Lightwave system is more elaborate.

[iainpunk]

another idea: using full spectrum optical sensors to read the blue or red shift of the colour spectrum of the strings, and then use an algorithm to extrapolate the real frequency.

cheers

[pinkjimiphoton]

dude, way above my paygrade,. remember, yer talking to pink here, and he's a blithering idiot

[iainpunk]

dude, pink, red shift and blue shift in light are quite simple concepts.

you know the doppler effect?
where the siren coming towards you has a higher pitch and the same one going away from you has a lower pitch? this same thing, but with light waves.
things that come towards you shift towards the 'blue side' of the spectrum, while things that move away from us shift towards the 'red side' of the spectrum.
this technique was used when they discovered that almost all stars are moving away from us.

cheers

[pinkjimiphoton]

[anotherjim]

The interesting thing if it's centred in the opto is string movement has the same effect coming or going. There is no positive then negative swingle cycle - it can only see more light or less light.
If the string is centred, it's probably going to have a dead spot and the opto transistor is mostly off. Everytime if moves enough to let more light in, the transistor turns on. It will do this twice per string cycle. That's going to give 2 transistor swings per string cycle that is double string frequency.
If the string is set to an edge of the beam, the transistor is mostly turned on. Every string cycle reduces light only once - no double frequency.

[deadastronaut]

this thing sounds sick.....

sustainer, / feedbacker.... nice one jimi.  mad little device...


the string influences the RX TX (leds) ?.  weird.

[duck_arse]

where am I going to find plastic tone-wood to make one of these?

[EBK]

where am I going to find plastic tone-wood to make one of these?

Everything sounds better on vinyl, of course!

[anotherjim]

where am I going to find plastic tone-wood to make one of these?

Hack a picnic table. All ours are recycled plastic these days but look like wood. Only available in mahogany or ebony though - never seen any maple.

[pinkjimiphoton]

The interesting thing if it's centred in the opto is string movement has the same effect coming or going. There is no positive then negative swingle cycle - it can only see more light or less light.
If the string is centred, it's probably going to have a dead spot and the opto transistor is mostly off. Everytime if moves enough to let more light in, the transistor turns on. It will do this twice per string cycle. That's going to give 2 transistor swings per string cycle that is double string frequency.
If the string is set to an edge of the beam, the transistor is mostly turned on. Every string cycle reduces light only once - no double frequency.

that would probably explain why when its working, it blooms up an octave. neat! so maybe it doesn't need to be centered directly over it? this thing gets curiouser and curiouser!

btw, the pot is 8k, not 10. 10 was the closest standard value. i DID actually find a nos 8k pot completely by accident yesterday at a surplus electronics site and ordered one.

i still can't wrap my head around how the hell this thing could possibly work tho

[Elektrojänis]

I don't see this mentioned so... One possible surplus/recycling source for this kind of sensors are computer mice. Modern optical ones only have one for the scroll wheel. Older ones that have a ball in the bottom have at least two, or even three if there is a scroll wheel too. The sensors in the computer mice actually have at least two phototransistors per unit though and possibly two leds too. That's because they have to sense the direction of the movement of the slotted disk that's positioned between the phototransistors and leds. I bet those could be used for this kind of thing too... You don't need to use both phototransistors.

And the sensors in even broken mice are probably still working as most likely part to fail are the buttons. And some get discarded as not working just because there is too much dirt in them.

[pinkjimiphoton]

petri!!

you're a GOD!!!

awesome idea... now i gotta find an old mouse kicking around!!

[pinkjimiphoton]

think this would work, with an led above or below it?

https://www.surplusgizmos.com/Osram-Laser-IR-infrared-NPN-Phototransistor-sensor-Model-BPX-43-4-BPX43_p_1859.html

the above needs this i think:

https://www.surplusgizmos.com/Infrared-Phototransistor-Model-UT0395-46-0125_p_1906.html

or maybe this?

https://www.surplusgizmos.com/TCRT5000-IR-Reflective-Optical-Sensor-wTransistor-Output_p_2551.html

[Jarno]

They haven't been really popular I guess, but I do recall the ads for bassguitars with the Lightwave optical pickups in the 90's, REALLY finicky to set up apparently.
Haven't these been reverse engineered yet?

[anotherjim]

Other sources to rob Opto-interrupters are floppy drives (5 1/4" most likely) and printers/fax machines.
I can't help thinking there might have been commercial types with pinholes to detect the travel of something that fitted the hole but I can't find any.
Since it's an IR sensor, it doesn't mind ambient light, so experimenting with an open slot type shouldn't be too difficult.