Gallery, Projects and General > Project Logs
Diy optical pickup for guitar -- is it possible?
sorveltaja:
After looking at the datasheet of 4093 ic, by lowering its supply voltage, the input threshold lowers also.
At 9V it is ~ 1,8V, and at 5V ~ 0,9V. By adjusting the 50k pot, there is a very narrow spot, where the output appears. Lower supply voltage makes that spot even narrower.
Multiturn trimmer pot could be a better choice for that, as they aren't that costly nowadays.
So far, circuits with minimal parts count are used. As I mentioned earlier, this thread is useless without pictures, but even more so without audio clips.
The mechanical setup isn't up for that yet, and needs a lot of testing as well. By using the current (flimsy)setup, it should be possible to use a least two strings, to make some nice sounds audio output.
The form of output, that I expect, could be fuzz/buzz. If all goes well, there should be some form of cross-modulation, that one gets only by using hex-fuzz.
PekkaNF:
--- Quote from: sorveltaja on December 18, 2019, 07:20:25 PM ---.....By adjusting the 50k pot, there is a very narrow spot, where the output appears. Lower supply voltage makes that spot even narrower.
Multiturn trimmer pot could be a better choice for that, as they aren't that costly nowadays.
.....
--- End quote ---
Normally trimmers are used only on fine tuning and discrete resistors are used to bring the trimmer "on range". This is because trimmers are not that stable and adjustment is easier if the adjustment is not ruined if a fly sneezes across the room.
This is probably all familiar to you?
https://www.electronics-tutorials.ws/resistor/potentiometer.html
After you find the sweet spot with that trimmer you can find min/max range that is likely to be usable and then calculate to measure the legs resistance and use that to find needed discrete resistors and new trim pot size.
Second thing is that schmitt triggers pretty generally require "reasonable" signal - i.e. they don't have amplification. That means that if your signal level is small you need to boost it before schmitt trigger. Amplifier also gives you possibility to bias signal if it has a DC-component that would drive that amplified signal into saturation. You have used a capacitor, but sometimes that is not without problems and you might need that signal DC-component later to actively control led current to stay in linear region.
sorveltaja:
Pekka, thanks for the link. Yes, using fixed value resistors is in the plan, although on the thinnest strings, which have less sustain than thicker ones, finding closest resistor values could be a bit tricky.
On a second thinnest string, when tested with 100k pot, at the sweet spot, it was removed from the circuit, and its values were measured, being close to 60k/40k, or 40k/60k.
The supply voltage was lowered to 5V, but before testing all the six circuits together, I can't tell, if it's the the final value.
Other than that, I drew some sketches, considering the mechanical setup. The electromagnetic humbucker pickup was remover from the guitar, to make more room.
One thing, that has bothered me about current mech setup, is that you have to drill holes through the guitar to make connections to the pcb.
A small step in hopes to change that:
[ You are not allowed to view attachments ]
In that pic, sender ir-leds' common ground legs are brought together with pcb trace. The 2-pin grey headers, where the leds are to be connected, should be identical size in length.
But as I have long ones(40 pin), they should be sawed off of that, and milled to size using depth jig.
There is ~4mm space below the headers, so small 1.6mm pcb should fit there. Not sure though, if there is enough room for all the traces for optical components, when using single-sided pcb.
But as always, I have to test it to find out, how far I can get.
I guess that there is an option to order custom made pcb's, but from what I've read, in this country, they would cost ~200€/piece. Or maybe I'm missing something.
But that aside, to provide more constant signal from the strings, while testing one by one the outputs, could be to use a motorised piano-hammer-like contraption instead of tickling the strings with fingers and toes for the purpose. That may well be the next side-project.
sorveltaja:
First test with a pcb, that may end up to the pickup housing:
[ You are not allowed to view attachments ]
Thinnest traces are 0,5mm wide, and it took quite a few times to get them to transfer without cracks:
[ You are not allowed to view attachments ]
Of course, the continuity of every trace has to be tested, before cropping the pcb to its final size.
sorveltaja:
Using parts of the header(mentioned earlier) to connect the optocomponents seems to be way too complex for this project.
I guess it could be done, but cutting 2-pin headers to the exact length would take huge amount of effort.
Reason for using parts of headers was to keep the led/phototransistor pair somehow 'aligned', when adjusting their vertical/height position.
On to the next version, which rely on using two hex-head screws as vertical 'rails'. The first printed version of that was too loose for the led/phototransistor combo to stay in place.
There is a discussion on the 3d-printer thread about snap-fitting printed parts together. That's where I got an idea for this:
[ You are not allowed to view attachments ]
At first, the red screws couldn't hold the green part in place, when they were adjusted.
Then came the snap-in thingy;
[ You are not allowed to view attachments ]
Screws were pushed into the green sender/receiver housing. It took some force, but once in place, the overall construction is surprisingly stiff. And for me, that was only the first test using snap-in fit.
As the green part(height) needs only a minor amount of movement to find the 'set-and-forget' -position, wearing the printed parts out shouldn't be problem. But time will tell.
Navigation
[0] Message Index
[#] Next page
[*] Previous page
Go to full version