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[Question] How to get -5V to +5V from a knob?
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blue hell
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Joined: Apr 03, 2004
Posts: 24075
Location: The Netherlands, Enschede
Audio files: 277
G2 patch files: 320

PostPosted: Sun Nov 09, 2008 9:16 am    Post subject:
Subject description: sorry for this primitive question but I don't know any thing about electronics
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When you have a negative supply already present (like -15 V) you can use a negative voltage regulator like the 79(L)05.

When you only have positive voltages present in your device you'll need to use a voltage inverter to make a negative supply yourself. For instance : http://www.reconnsworld.com/power_voltinvert.html would do that. And then use a 79(L)05 after that to regulate down to a stable -5 V.

However when your circuit does not use negative voltages currently you have to be careful to not put negative voltages into it, as this would make you go below ground and that could cause damage to your circuit.

_________________
Jan
also .. could someone please turn down the thermostat a bit.
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blue hell
Site Admin


Joined: Apr 03, 2004
Posts: 24075
Location: The Netherlands, Enschede
Audio files: 277
G2 patch files: 320

PostPosted: Sun Nov 09, 2008 4:50 pm    Post subject: Reply with quote  Mark this post and the followings unread

You'd connect +5 V to one end, and -5V to the other end of the pot. The wiper is the output. Typically the input impedance of a synth input is 100k, you'll want to much lower than that to avoid loading the pot too much ... I'd pick 1 k to 10 k, but not higher.

As in :

Code:


  + 5V ---+
          |
         +++
         | |
         | |<---o------> to synth
         | |
         +++
          |
  - 5V ---+
           


_________________
Jan
also .. could someone please turn down the thermostat a bit.
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Kenneth



Joined: Apr 16, 2009
Posts: 43
Location: Stockholm, Sweden

PostPosted: Thu Apr 16, 2009 10:01 am    Post subject: Reply with quote  Mark this post and the followings unread

Xiaodaner wrote:
Thanks a lot!

I've found this buffered voltage source circuit here:
http://www.bitshifted.com/synthdiy/CVSource.html
Hope this helps other ppl as well.

Regards,
/Xiaodaner


Yes, me, I'm trying to grasp the basics as well and had thoughts about this usage of a pot earlier today; "can I put -V in one end and +V in the other and use the slider to choose? or will the pot go kaboom?", now I know it wan't and that is how it is done, wery nice Smile
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