touch interface projects ?

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flab
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touch interface projects ?

Post by flab » Tue Aug 01, 2017 8:56 am

Hi boys and girls,

I was hoping to help me identify what touch interfaces are on the market,

could me like touch keyboards, like buchla verbos etc

but i am more interested at the touch points like, lyra 4/8 or others(?).

i would like to build a touch interface like Lyra s have, for my osc, and i was thinking what circuit is? Is basically the body of the mechanical part and my skin creating a resistance , connected directly to the v/oct or should i add any circuity at the path

thanks in advance
Petros

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Post by Jarno » Tue Aug 01, 2017 9:00 am

Image

I made this, but it is a bit of a hack and is really just latching switches, using this touch IC.

So no CV out, just gates. I isolated the solder points with hot glue, so yeah, classy.

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Post by lasesentaysiete » Tue Aug 01, 2017 9:01 am

I recently ordered the Korb Pusher pcb/panel for eurorack. It uses touch sensitive resistors to output cvs and gates. Its an Arduino-based circuit.

There's another similar module by Synthwerks that uses an Arduino, I think. THe Buchla touch keyboard by Roman also uses a microprocessor. Seems most recent implementations of this idea are digitally controlled. The lyra touch thingies are not, though.

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Post by adam » Tue Aug 01, 2017 9:28 am

[video][/video]

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ersatzplanet
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Post by ersatzplanet » Tue Aug 01, 2017 2:50 pm

We at Synthwerks make a whole line of modules based on Force Sensing Resistor (FSR) technology. These sensors are very responsive and are not affected by skin resistance or calluses and can be operated with gloves on or with drumsticks. Almost all the dynamic sensing in pad-style controllers and sequencers are using FSR technology and most Keyboard aftertouch systems use them. You can tailor the feel and response by using foam pads or mats on them (I use old cut up mouse pads).

The main family:

Image

Also a newer single pad version with a built in electronic switch on top of the standard level sensitive gate out -

Image

And a dual passive version -

Image

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woodster
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Post by woodster » Tue Aug 01, 2017 4:14 pm

Does the XIIO count -

viewtopic.php?t=172466&start=0

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flab
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Post by flab » Tue Aug 01, 2017 4:19 pm

Thanks for all the suggestions, as a diy head i knew several projects as well , though i wasnt clear enough,

i would like to make my own interface,

so i guess i a looking for some kind of directions in how to tackle the mater, how to produce cv by physically touching a body/contact amplify it etc. arduino is one way to go as well. maybe a schematic you can suggest to me as well

Regards

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jmagin
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Post by jmagin » Tue Aug 01, 2017 4:45 pm

Touch, not pressure is typically detected in two basic ways:
- Resistance where two contacts are bridged
- capacitance

(not counting touchscreens, or other complicated x-y grid situations), I think most modern commercial products that do some sort of touch sensitive button are capacitive. The difference in the capacitance to a common frame of reference (e.g. ground) of a untouched few-square-centimeter pad and a pad that is being touched by a person (or is strongly capacitive coupled to them, such as through a thin plastic sheet is easily 1-2 orders of magnitude.

Atmel, for example, has some dedicated ICs (QTouch) to do touch sensing and some hardware+software support in some of their microcontrollers as well. Somewhat crudely you can do this in any random microcontroller though, using one or two pins per touch sensor. Essentially you just discharge the sensor and measure it's time to charge from a current source (or vice versa).

Trickyness includes:
1. Avoiding ESD damage to your microcontroller (most are fairly robust, but you usually want at least some series resistance from the sensor to protect the protection diodes, also, this is where an insulating layer between the sensor and the human helps in commercial designs)
2. Auto calibration
3. quick response
4. interference rejection (both 50/60hz mains hum, which will be worse if the device is not grounded and interference from nearby switching power supplies, radio transmitters, etc.)

There are some inevitable engineering tradeoffs among 2/3/4. I think a lot of this is where the widely-reported Maths sensitivity issues occur. I'm slightly disappointed in myself for not spending some time reverse-engineering that aspect of Maths during the short time I had one -- I was somewhat curious whether they were using some fairly off-the-shelf commercial approach or if it was strictly roll their own.

(There are also pre-microcontroller touch schemes -- I think old touch-sensor table lamps and the Wasp fall into this category -- often built using generic CMOS ics or darlington pairs of transistors to get sufficient gain -- either measuring the resistance across two contacts, or intentionally rectifying and low-pass filtering the coupled mains hum to get a touch signal.)

Edit: also besides the charge-time-measurement scheme, you can certainly measure capacitance also by how much the sensor is loading a high frequency oscillator, I think that's the scheme at work in https://www.cgs.synth.net/modules/cgs86_trk.html

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Post by Silicium » Tue Aug 01, 2017 5:41 pm

Something like Verbos TouchPlate as DIY would be so nice.

CGS86 is a great start but with touch sensitivity and/or position detection for bend i would kill.

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Post by flab » Wed Aug 02, 2017 11:40 am

adam

that is an interesting approach , thanks i will have a closer look for arduino solutions, i have no idea from digital devices but a friend of mine does.

mmagin
thanks for our msg

i do agree guys cgs 86 is a nice project, what is the interface ade of pcb, or ?

Also a question, why would be rong to have a o contact point, lets say a screw or a copper surface, then this wired to an op amp with a pot to adjust the 0-5v passing though every time you touch the surface? and series of those, as many as you need for your CV devices ? sth like a microphone i guess ?

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Post by windspirit » Wed Aug 02, 2017 1:47 pm

Heres a vote for the xiio, really nice touch pad project with a bunch of features like a togglable gate out and an arpeggiator built in.

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Post by old gregg » Wed Aug 02, 2017 2:17 pm

I'm working on this at the moment, which is the pressure point idea but minus the pressure sensor. It's very basic and used cheap logic ICs (CD4013/CD4066 for the logic part). the metal strip could be exposed copper on the pcb.

Image

Although It hasn't got any additional features a microcontroller based module would have. There's some pretty interesting one for that application with capacity sensor.

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Post by cygmu » Wed Aug 02, 2017 6:16 pm

flab wrote: i do agree guys cgs 86 is a nice project, what is the interface ade of pcb, or ?
Yes, the pads are a PCB (CGS86PAD). It's 16 pads on a Serge-style 1" spacing. You can cut the board in half to make an 8 pad board. It wouldn't be too hard to design your own pad board if you prefer other dimensions and use the CGS86 and CGS86D to make it work.

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Post by flab » Thu Aug 03, 2017 3:50 am

old gregg
nice looking good, would you like to share any details at your project?

windspirit
I am not interested in getting a ready project, i alost got the project 3 months ago, but i canged my mind.

cygmu

i would love to do a design similar for my synth (eurorack) and use a schematic maybe similar to the cgs 86, or maybe try to tacle the project with arduino, and be my intro project to digital design worldImage

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Post by flab » Thu Aug 03, 2017 4:07 am

there is also this version of the cgs 68 in euro from elby http://www.elby-designs.com/contents/en ... board.html

and a really interesting thread in electro-music forum, so uch knowledge in there http://electro-music.com/forum/topic-27866.html

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Post by AonFLuX » Thu Aug 03, 2017 4:09 am

adam wrote:[video][/video]
HAHa! Nice one! :banana:

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Post by old gregg » Thu Aug 03, 2017 3:56 pm

old gregg
nice looking good, would you like to share any details at your project?
I planned to publish the schematic once the module is working. It's very simple stuff. Here's a snapshot of the test I made in SPICE, the design I made is a bit different tough.

https://smokingtip.files.wordpress.com/ ... _spice.png

the shmitt trigger signal goes into a CD4013 flipflop that on/off a bunch a CD4066 switches.

I won't redo something like that, too much components. I'll rather use a touch capacity sensor micrcontroller.

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Post by daynehacks » Thu Aug 03, 2017 11:30 pm

I wish there was something DIY like the makenoise modules. Their PCB touch interfaces look really cool.

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Post by ClausF » Fri Aug 04, 2017 12:43 am

old gregg wrote:
old gregg
nice looking good, would you like to share any details at your project?
I planned to publish the schematic once the module is working. It's very simple stuff. Here's a snapshot of the test I made in SPICE, the design I made is a bit different tough.

https://smokingtip.files.wordpress.com/ ... _spice.png

the shmitt trigger signal goes into a CD4013 flipflop that on/off a bunch a CD4066 switches.

I won't redo something like that, too much components. I'll rather use a touch capacity sensor micrcontroller.
Sorry, what is V1 and V2?

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Post by flab » Fri Aug 04, 2017 3:11 am

daynehacks
you will find the korb module and the ixxo one , very similar to pressure points.

but yes i would love one y self as well,next month i wil have some tie i will invest to start this personal project

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Post by old gregg » Fri Aug 04, 2017 10:32 am

ClausF wrote:
old gregg wrote:
old gregg
nice looking good, would you like to share any details at your project?
I planned to publish the schematic once the module is working. It's very simple stuff. Here's a snapshot of the test I made in SPICE, the design I made is a bit different tough.

https://smokingtip.files.wordpress.com/ ... _spice.png

the shmitt trigger signal goes into a CD4013 flipflop that on/off a bunch a CD4066 switches.

I won't redo something like that, too much components. I'll rather use a touch capacity sensor micrcontroller.
Sorry, what is V1 and V2?
V1 is a serie a pulses to simulate the bouncing introduced by the finger on the plates. V2 is the 12V power supply.

basically the pulses charges the capacitor until it reaches the schmitt triggers threshold to change its output state. All the reste depends on this output.

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Post by ClausF » Fri Aug 04, 2017 11:13 am

Thanks old_gregg, understood :razz:

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Post by thx2112 » Fri Aug 04, 2017 7:19 pm

I used the CAP1188 (two, actually) for the CV Touch tile module.

I initially tried using the built-in Atmel capacitive sensing but it was too finicky -- especially in a noisy Eurorack system. The specialized ICs auto-calibrate on startup and the CAP1188 has built-in LED drivers which enabled the CV Touch to run off of just an 8-pin Attiny. CV is generated from a 12-bit DAC on the same I2C bus as the CAP1188.

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Post by schwittersplayspop » Fri Aug 04, 2017 11:21 pm

Landscape AllFlesh seems novel:

http://www.landscape.fm/allflesh/

I can recommend the Razmasynth Unknown Pleasures as well.

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Re: touch interface projects ?

Post by GKMendenhall » Fri Oct 16, 2020 12:20 pm

I built this box—https://www.instagram.com/p/B-xJjE8n8ZT/—using the schematic from DIY Synth Guy on Youtube. Basically quadrupled his design and made it run off of a 9V guitar pedal power supply. I etched the copper pads using muriatic acid and hydrogen peroxide. When you touch to pads, you complete the circuit so no matter where you touch, you get the same effect. It is pressure sensitive in that when more of your hand contacts the plate, it outputs a higher voltage. The knob attenuates the signal. Another cool aspect of it is that you can blow hot air across the pads and it works. As the moisture evaporates, the signal fades. I'm working on a new version.

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