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diy cv joystick? paia oz bender?
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ryan



Joined: Jul 06, 2006
Posts: 2
Location: chicago

PostPosted: Thu Jul 06, 2006 7:22 pm    Post subject: diy cv joystick? paia oz bender? Reply with quote  Mark this post and the followings unread

Hello. I'm looking to build a very basic joystick controller to work with my korg ms-10 and paia 4700. It would be really nice if it would work with the arp 2600 and moog modulars at my school as well. I have practically no electronics experience, but am eager to learn. Is this something that would be feasible? Does anyone have any advice? Also the bending pad on my paia oz is missing. Does anyone have any suggestions for a replacement? Thanks.
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DrJustice



Joined: Sep 13, 2004
Posts: 2052
Location: Morokulien
Audio files: 3

PostPosted: Fri Jul 07, 2006 8:10 am    Post subject: Reply with quote  Mark this post and the followings unread

Ryan,

welcome to electro-music.com!

The basics for CV performance controllers is just a potentiometer connected between the positive power supply and ground. A joystick has two potentiometers, one for each axis, so we're looking at something like:
Code:

   0  +V                          0  +V                       
   |                              |                           
  +-+                            +-+                           
  | |<-------0 X axis CV out     | |<-------0 Y axis CV out
  +-+                            +-+                           
   |                              |                           
   |                              |                           
   0  0V, ground (or -ve)         0  0V, ground (or -ve)
       

The potentiometers can also be connected between a positive and negative supply voltage for bipolar operation.

If your power supply is +/-15V and you want a CV range of +/-10V, as often is the case with modulars, then you can set up a voltage divider like this:
Code:

   0  +15V
   |
  +-+
  | |  5k ohm
  +-+
   |
  +-+  20k ohm
  | |<----------0 Control voltage output
  +-+
   |
  +-+       
  | |  5k ohm
  +-+
   |
   0  -15V



The total range of the shown power supply voltage is 30V, so we divide this voltage over 2 resistors and the potentiometer, choosing values such that we end up with a range of 20V across the potentiometer to give us the +/-10V CV output. I.e. we get rid of the extra 10V by 'shaving off' 5V at each end using the two resistors.

Read more about potentiometers and voltage dividers.

If the power for the joystick can not be derived from the internal power supply of the synth, then you can use an external power supply. In this case that external powers ground must also be connected to the synth together with the CV (many systems allow the use use of the ring of the patch chord jacks for ground).

Find out what CV signals are appropriate for your synths, determine whether you can use the internal power supply or not and choose resistors and potentiometer values accordingly, and Bob's you uncle.

DJ
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ryan



Joined: Jul 06, 2006
Posts: 2
Location: chicago

PostPosted: Fri Jul 07, 2006 8:45 am    Post subject: Reply with quote  Mark this post and the followings unread

thank you so much for your info. this site seems amazing!
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Yorky



Joined: Feb 14, 2005
Posts: 244
Location: Boston, UK

PostPosted: Tue Sep 26, 2006 1:24 pm    Post subject: Reply with quote  Mark this post and the followings unread

I'd be tempted to pop a simple voltage follower on the output to buffer the voltage

Also run the 'input' voltage from a stabiliser or at least a simple zener, to give stability

_________________
Lots of new albums at Ambientlive
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danielwarner



Joined: Dec 18, 2006
Posts: 65
Location: Sacramento

PostPosted: Wed Feb 06, 2008 10:51 pm    Post subject: Reply with quote  Mark this post and the followings unread

I recently acquired a couple of RadioShack TRS-80 joysticks at a thrift store, they have MIDI-style 5-pin DIN plugs and they're potentiometer based, and they each have a push button as well.

So I'm assuming the wiring is something like... one pin supplies +V, one pin is a return to ground, one pin is X-axis CV, one pin is Y-axis CV, and the fifth pin is a gate controlled by the push button?

I'm building a modular, it'd be awesome to make a simple module where I could plug those two joysticks in and get 4 CVs out!

Would anyone happen to know any sort of website that might give me the DIN plug pinout for a TRS-80 joystick? I did some Googling, to no avail

I guess, hey this is DIY, I may have to just throw it on a breadboard and figure it out for myself... but it's always nice to rely upon information made previously available if at all possible.
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DrJustice



Joined: Sep 13, 2004
Posts: 2052
Location: Morokulien
Audio files: 3

PostPosted: Thu Feb 07, 2008 7:50 am    Post subject: Reply with quote  Mark this post and the followings unread

I found the pinout for the CoCo joystick port here. With a bit of luck it's the same as the TRS-80 except for the 6th pin with a fire button 2 signal.

DJ
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danielwarner



Joined: Dec 18, 2006
Posts: 65
Location: Sacramento

PostPosted: Sat Feb 09, 2008 10:52 pm    Post subject: Reply with quote  Mark this post and the followings unread

Ahh, hopefully you're right, the pinout will be the same minus pin 6. I need to get some DIN jacks and breadboard this!
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