touch control

[fetideye]

I want to add touch control for the volume of my lunetta oscillators.

I was thinking to use DIY vactrols for gain control in combination with a cd4069 or 4049,
The touch pad would turn on the LED and if there would be a decay control, that would be nice.

What would be a good way to do this?

This is my progress so far:
https://tinyurl.com/yn6vcsn6
better one?
https://tinyurl.com/yqcgg3ae

[ianbax]

I'd say you're pretty much there.

For the touch switches I've been experimenting with the little red ones that are all over ebay/amazon etc based on the ttp223 chip (thanks to Phobos for this tip there's a thread on it https://electro-music.com/forum/topic-73837.html)

Here's a random ebay link but as I said they're easy to track down in several quantities:

https://tinyurl.com/4jw5r3v3

They're self calibrating and plug and play - straight out of the box (although I am working at 5v) they produce a momentary logic high when touched.

I've actually got a similar 'vactrol controlled amplitude' hooked up which is based roughly on Nicolas Collins vactrol tutorials (https://www.youtube.com/watch?v=WyQMvSLTC4Q)

I chose an LDR with an insanely large dark resistance (2M I think) and set up a fading LED circuit similar to your falstad link - although mine has attack and decay.

I think you'd just have to fire up the transistor switch with the little red touch pad - perhaps buffer it ?

For the 'audio' side I buffered the signal going in (square wave from a 4093 type oscillator) using a 4049 (4069 here, but 4049 is what I had https://hackaday.com/2015/03/09/logic-noise-sawing-away-with-analog-waveforms/ )

and I found a diode facing the LDR on the way in made for complete silence (because of the voltage drop?) when the LDR/LED combination was dark.

I even found that a capacitor to ground after the LDR gives a crude low pass gate type sound.

Does that make sense? I'm afraid I never drew a proper schematic up, just my scribbing in a notebook.


But...if you don't want to go the vactrol way and you're only processing lunetta square waves there's a psuedo VCA on the hackaday series (https://hackaday.com/2015/04/10/logic-noise-more-cmos-cowbell/) although I've never tried it myself. I think you just need to trigger it from the touch pad output at the right point (where his schematic says 'square wave in'?)

[fetideye]

thanks!

I'll look into those capacitive sensors. It would be cool te know the schematic of those, to integrate it on my panel

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[fetideye]

Thanks, these are helpful
I'll try 'm out!

I'm looking for touch gate / triggers to control the volume of the drone synth (several channels of tuned (and chopped up) triangle waves, so it is not a squarewave or digital source.