Author Topic: working out a buncha-knobs-want-presets kind of problem... digipots? vactrols?  (Read 5981 times)

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deadastronaut

cheers gary, nice one,

i had midi notes out of it into my proteus 2000 last night...a good start.. 8)

i found a nice simple 6 pad/piezo trigger for midi drums (with velocity sensing)
and  just got some piezos to play with...looks like fun..

the arduino mega looks really cool with 16 possible pads...excellent. 8)
i have a nanopad2 with 16 pads which is great , but i really want something i can whack/bigger pads etc.. :)

anyway, i'll have a crack at this today..(schematic @ 2:24.)

https://www.youtube.com/watch?v=vi-w_WqJjzQ

i also read that i could use a multiplexer 4051 to expand the inputs for more drums, so i have 2 of those handy now too..but i may just get the arduino mega for 16...hmmmm..

anyway, been looking at various projects, loads of possibilities, nifty stuff

but haven't a clue with the code lark , ( apart from tinkering with ready made values ;))


also got a LCD DISPLAY to write abusive stuff on too... ;D








http://www.youtube.com/user/100roberthenry
http://deadastronaut.wix.com/index
https://deadastronaut.wixsite.com/effects

^ SPACE PATROL FUZZ/ NANO-8 MIDI DRUMS /CHASM REVERB / TREMSHIFTER / FAZE FILTER/ABDUCTOR II DELAY pcb's + WAH LIGHT PLATES. and sausa

samhay

>It's new.. I don't expect new products to be available in through hole anymore. I think we need to bite the bullet and find ways to handle these tiny packages
>Yeah, adapterboards are essential as we like to breadboard our stuff first ( I do ) ...

I don't expect many new chips to be through hole, but I thought I would mention it seeing as it may provide further difficulties for the OP (and others). In general I don't mind SMD, but it is a PITA to have to get the soldering iron out before you can play on the breadboard, so I tend to try to find TH alternatives when I can.



I'm a refugee of the great dropbox purge of '17.
Project details (schematics, layouts, etc) are slowly being added here: http://samdump.wordpress.com

garcho

Quote
but it is a PITA to have to get the soldering iron out before you can play on the breadboard

that's really the only thing that scares me about SMDs. i imagine there will soon be many creative solutions:


"...and weird on top!"

~arph

Very cool!  reminds me of a pcb test jig

snarblinge

Apologies for pulling up this old thread, but best place I thought, also wouldn't mind an update on where anyone got to, mine is still on the bench

Considering having a play with one of these, I'm sure fun can be had

http://www.oddwires.com/pt2322-6-channel-audio-processor-ic/

http://oddwires.blogspot.co.nz/2012/07/using-arduino-pt2322-library-for-audio.html

b.

snarblinge.tumblr.com

MR COFFEE

If you want to use digitally controlled pots without driving yourself crazy with SMD smaller than SOICs,
the X9C104 is still available in 8-pin DIP and SOIC packages - you might have to hunt for the DIP ones, but a SOIC-packaged part is sold mounted on a  8-pin "DIP" pcb with a few onboard components (capacitors) from Sparkfun and on eBay. The only supply voltage is +5volts, but the signal range is +/- 5 volts (i.e., a 10 volt signal range if you bias it at Vcc/2). That is less than a 9 volt power supply, so they will work without vactrols or other workarounds.

In case you are wondering how Intersil got a +/- 5v signal range with a 5v power supply, they use an internal charge pump to bias the "wiper" switches.

mr coffee

ElectricDruid

There's another possibility which no-one mentioned originally, which is using CMOS switches controlled by a PWM waveform as a pot. There are plenty of PWM phaser designs around here that use a single switch as variable resistor, but it's just as possible to set up a pair of switches to make a complete potentiometer. The two switches are fed with inverted PWM signals.

This kind of thing used to be a pain to do (witness the hideous mess of LFO+PWM circuitry in PWM phaser pedals) but with AVRs/PIC/arduinos it becomes many times easier and uses far less parts.

Tom

Eddododo

There's another possibility which no-one mentioned originally, which is using CMOS switches controlled by a PWM waveform as a pot. There are plenty of PWM phaser designs around here that use a single switch as variable resistor, but it's just as possible to set up a pair of switches to make a complete potentiometer. The two switches are fed with inverted PWM signals.

This kind of thing used to be a pain to do (witness the hideous mess of LFO+PWM circuitry in PWM phaser pedals) but with AVRs/PIC/arduinos it becomes many times easier and uses far less parts.

Tom
I like the sound of this, but I've never wrapped my head around  PWM applications... I guess it's time I do

ElectricDruid

The basic principle is simple enough to understand. The switch has an on resistance and and an off resistance (which you'd often tweak with further external resistors) and varying the duty cycle gives you an "average" resistance which is between those two limits. So with a narrow 5% pulse wave, you're very close to off all the time, and you'll get only a shade less than the off resistance. With an 80% pulse wave, you're switched on 4/5ths of the time, so the resistance goes way down almost to the On resistance.
The "average" part requires that the PWM frequency is sufficiently higher than any signal that you might feed through the switch, otherwise you'd just have built an OTT chopper tremolo!

HTH,
Tom

MR COFFEE

PWM is more trouble than DPOTS because of the details of filtering the modulation frequency back out without turning into audible noise.

If you want to investigate PWM, search for INNOVONICS schematics. They did a compressor for radio stations around the world without any unobatanium parts that functioned very well.

mr coffee
Bart