mattell starmaker guitar, with optical pickup system...

[pinkjimiphoton]

so in my stupidity and lust, i picked up one of these things over the last few days for entirely too much money.
its a cool little toy i remember spending a few d-lysergic energized days playing with many decades ago, like, a one string diddly bow that feedsback on itself using an onboard speaker and an optical pickup system.
tonnes, i mean TONNES of fun... and maybe a fun excercise in diy stuff...

anyways, came in last nite. it works, kinda, but not right.. it appears the optical pickup has shifted slightly out of alignment with the string, so i gotta sus that out to make it work right.

the whole thing is driven by... you guessed it... an lm386n.

since i have it apart already, i figured i'd take some pics if anyone is interested in making one, or making
a one string diddly bow. the optical pickup is cool... there's basically an infrared led and a reciever, and the string vibrates and is picked up by them.

i'll try and get some gut pics when i head down the dungeon shortly.

https://www.youtube.com/watch?v=bkW4CJjthO0

[GibsonGM]

I'd like to see how that works...maybe make something for the little ones or something!

[pinkjimiphoton]

parks,
think of a one- string diddly bow with a fernandez sustainiac, and that's pretty much what ya got here

i'll get some pics up asap!

[Rob Strand]

think of a one- string diddly bow with a fernandez sustainiac, and that's pretty much what ya got here

i'll get some pics up asap!

The feedback is just the vibrations from the speaker on the thin top plate, yes?

[pinkjimiphoton]

sorta. when the string is actually aligned over the sensor properly, its feeding back like a sustainiac in the octave position. if not, yeah, expected accoustic kinda feedback. the pickup can pick up the speaker, too.



thinking about adding a line out to it so i can plug it in a big amp
lol

[iainpunk]

would that be called a diddley e-bow?

now i wanna build a similar system. maybe a more banjo-like body, or an old cookie tin. don't know yet what i will use to feed signal back into the string. i would love a lead instrument with infinite sustain. maybe ill add a Jawari bridge and sympathetic strings tuned to a chord to add a buzzy drone underneath the lead tone

this inspiration really makes the cogs in my brain turn.

cheers

[GibsonGM]

I did a little checking - they're not hard to make. You can modify an old pickup and re-wrap it, then basically use a Fetzer/Ruby amp to drive it.   Coming up with some kind of body might be the REAL fun part!   This doesn't get into the "OPTICAL" part, though - that is what's got me curious with Jimi's.

http://diy-fever.com/misc/diy-sustainer/

[pinkjimiphoton]

gotta 2x4?   

[iainpunk]

Coming up with some kind of body might be the REAL fun part!

yes, i used plastic buckets, no dog poo signs, cigar boxes, and most ''famously'', a Mercedes Hub cap



the hubcap has gone through so many different iterations, i can't even remember all of it i guess. i have had that beauty for a bit more than 10 years, it originally used bolts and wingnuts that just pulled straight as its tuners, but needing a big screwdriver to tune a guitar wasn't ideal (big for enough torque) then i had low quality tuners, then i put in good tuners. it has been tuned everywhere from low A to a high G. there have been 5 different pickups, and countless ways i had them wired up.

building 'thrash' instruments is fun because it takes away some boundaries that modding a normal guitar often has.

cheers

[pinkjimiphoton]

i love it. a hubcap. awesome!!!!!!!!!   

ok here's pics


overall guts





back of the board



























i killed the furshlugginer!!! volume pot putting the %^&*suckin mother @#$%er back together, arrrrgh... til next time.
can't tell which of the sensor things is which... one is the led, one is the sensor for it. didn't wanna tear it apart and kill a 40 year old toy. the string passes thru that square thing, and has to line up pretty precisely with the led so it will track right. if its lined up perfect, the sucker is a thing of beauty and a lot of fun. if not, well, not so much.

lol

try and get video soon

[GibsonGM]

Iain, that thing is f&*&#$(  awesome, LOL!  LMAO - great job!

Jimi - thanks - I'm still trying to get what the opto does. Is that just a '386 amp like the DIY fever guy built?  That opto deal is acting like the 'pickup' somehow?

[Rob Strand]

sorta. when the string is actually aligned over the sensor properly, its feeding back like a sustainiac in the octave position. if not, yeah, expected accoustic kinda feedback. the pickup can pick up the speaker, too.

For you pics I'm pretty sure the vibration from the speaker makes it way to the bridge and the excites the strings.

The black thing is a photo-interrupter.  No doubt similar something like this.  I haven't seen an enclosed loop package like that.  I a can't say I've gone looking for one.  The other option is Mattel made their own, did the plastic mould,  and stuff in an LED and sensor.

https://au.element14.com/kingbright/ktir0611s/photo-interrupter/dp/2079964?msclkid=7072baf0a42917d0fe18db4e3c15a939&CMP=KNC-BAU-GEN-SHOPPING-SENSORS-AND-TRANSDUCERS

i killed the furshlugginer!!! volume pot putting the %^&*suckin mother @#$%er back together, arrrrgh... til next time.
can't tell which of the sensor things is which... one is the led, one is the sensor for it. didn't wanna tear it apart and kill a 40 year old toy. the string passes thru that square thing, and has to line up pretty precisely with the led so it will track right. if its lined up perfect, the sucker is a thing of beauty and a lot of fun. if not, well, not so much.

Damn that sucks.  Did you actually fry the sensor?

I suspect the circuit will be very simple.

https://www.electroschematics.com/wp-content/uploads/2014/06/photo-interrupter.jpg

If you trace the wires to the board the LED will have a low valued resistor in series and just got to + and gnd.
The sensor will have a high-valued resistor and a couping cap off the collector which will go the amp.
Variations on the theme are possible.     

No idea what wavelength they would use you could try firing a few remote controls into it.  If you hear some pips it might mean the sensor is OK.   For the LED you could just measure the voltage drop across in when it's powered up.

The output signal from the sensor could be hard on/off, that would be easier for production.    The other method is to back the LED current off a bit so the signal is more analog.  That means tuning the LED current and would be a pain in production for a mass-produced toy.

[pinkjimiphoton]

found this

https://www.madmodder.net/index.php?topic=13013.0

rob, naaah, i just f'd up the volume pot when i was stuffin the damn knob back on. i can fix it.

btw, i believe its b10k forgot to mention.
basically the pickup works by lighting the infrared led
and the infrared detector under it gets disturbed by the string vibrating somehow.
i saw a couple of things about it surfin a while ago, will try and find more info.

i've got it mostly working now i think, i do have to fix the pot tho.

[Rob Strand]

found this

https://www.madmodder.net/index.php?topic=13013.0

rob, naaah, i just f'd up the volume pot when i was stuffin the damn knob back on. i can fix it.

btw, i believe its b10k forgot to mention.
basically the pickup works by lighting the infrared led
and the infrared detector under it gets disturbed by the string vibrating somehow.
i saw a couple of things about it surfin a while ago, will try and find more info.

i've got it mostly working now i think, i do have to fix the pot tho.

Phew, that's good news.

I did this from your photos.

[pinkjimiphoton]

this is definitely what they're using as a pickup in it.




https://www.electroschematics.com/wp-content/uploads/2014/06/photo-interrupter.jpg

too late tonite, but will have to do some researching tomorrow. should be able to trace the connections to stuff to see where it hooks up. when its working, its kinda cool.

they used optical sensors on the yamaha g-10 guitar synth system, too.. but that thing had all kinds of crazy sensors. mine now lives with the godfather of us all, craig anderton.

[Rob Strand]

OK, I posted the trace.

No details on the photo interrupter but I added the wiring.

I like how they used the LED as a regulator for the opto output.  Stops some types of noise and keeps the level constant over the life of the battery.

[pinkjimiphoton]

too cool! rob, you're a madman, dude!

hey, check this out

https://www.diystompboxes.com/smfforum/index.php?topic=34825.0

and also this, which is where i saw this a ways back

https://makezine.com/projects/infrared-string-bass/

[pinkjimiphoton]

wonder if this would do the trick:

https://www.digikey.com/en/products/detail/rohm-semiconductor/RPI-352/638549?utm_adgroup=Optical%20Sensors%20-%20Photointerrupters%20-%20Slot%20Type%20-%20Transistor%20Output&utm_source=google&utm_medium=cpc&utm_campaign=Shopping_Product_Sensors%2C%20Transducers_NEW&utm_term=&utm_content=Optical%20Sensors%20-%20Photointerrupters%20-%20Slot%20Type%20-%20Transistor%20Output&gclid=Cj0KCQiAqvaNBhDLARIsAH1Pq51YuDnyQy1yClfOumAl5eENvXOcwpzoh9A0Y9vme_jB5jTzV_GpllwaAvChEALw_wcB


https://fscdn.rohm.com/en/products/databook/datasheet/opto/optical_sensor/photointerrupter/rpi-352.pdf

[Rob Strand]

hey, check this out

https://www.diystompboxes.com/smfforum/index.php?topic=34825.0

and also this, which is where i saw this a ways back

https://makezine.com/projects/infrared-string-bass/

The little hole idea looks interesting, perhaps better if it had its own light source.

I think there's two basic approaches.
- More of a digital output.  You block the beam of not.   Like the Mattel unit.  That's going to produce more of a square-wave, or at lease some non-linear waveform.  Think of this like a clipped transistor stage.
- Analog output.   The output is more than blocked or not blocked.   The output depends on the how blocked or unblocked it is.  You can imagine this is more like a string.  This is harder to get to work because the sensor needs to be biased at some bias point like the collector on a transistor amplifier.   It's still not that simple because if you hit the strings hard you still want this linear behaviour.  If the string moves to much it will be outside of zone where the sensor does something.   From what I can see the little hole method in the  thread you linked will have a larger range of linear behaviour.

https://fscdn.rohm.com/en/products/databook/datasheet/opto/optical_sensor/photointerrupter/rpi-352.pdf

I think you would have to try it.  If you look at the datasheet they show a range distances where the on/off-ness goes through a transitional regions, perhaps 0.5mm to 1mm wide.   I'm not sure what spec you need to sound good.    If you look at the datasheet I posted earlier it's similar but different.    I sure some of those interrupters will sound better than other.   It might even depend on the string diameter.

Another variable is offsetting the string.    You can imagine the rest position is blocked then it leaks light across as the string deflects (either up or down).  Or you can start with the beam barely allowed to pass then it kind of lets more light across in one direction and block more in the other.

You can play with this stuff for hours.  So many variables.

[pinkjimiphoton]

for some reason, this last pic didn't show up yesterday when i emailed them to my phone




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 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.

this is kinda a cool little gizmo. be nice to find a way to exploit it nefariously for more fun toys to mess with