next topic »

[on:]

Hi,
I want to control variable resistances (2-10-50-100K, 1MOhm) in circuits via my computer (replace a pot by a software control).
I have read about digital potentiometers but in my case I have circuits powered at 9v and 12v (and with double power 9v/-9v/0v …) …
There used to be digital potentiometers up to 15v in DIP (Dual Inline Package), but they seem discontinued…
I suppose there is a case-by-case solution without using digital pots: I have 2 chaos generators circuits (see attached images) where i need computer control over the potentiometers.
The one called chua is more simple, there is only one variable resistance to control (1.5 or 2k):

The one called Jerkster is more complex with several variable resistances (R14,R21,R24,R2,R22):

Any solutions for these examples? Any digital pot in DIP package with up to 12v operation available? Any examples with schematics are very welcome!
Thanks,
Felix

[Reply #1 on:]

You can use CMOS switches and fixed resistance, is not very accurate but it is simpler and more flexible

[Reply #2 on:]

Hello Edsoncan,
Thanks for your quick input.
There seems to be a lot of types, could you please explain me more in detail witch kind of CMOS switches should I use and point me to some specific models?
And how should I connect it to my 0-5v Arduino to control the CMOS switches as a variable resistance?
A schematic will be of great help, if someone can make it …  
Thanks
F

[Reply #3 on:]

[Reply #4 on:]

@Edsoncan - if he connects that to a 12 volt circuit he will blow up his arduino. That is only good for 5V circuits.

[Reply #5 on:]

Edsocan, thanks for the schematics!
Mike, thanks  for pointing that detail ;-)

I'm new to Multiplexers/Switches, and i don't get exactly how they work in this configuration... But are we using it as a voltage controlled resistance?
If it's the case, to work with the arduino and a make a 12v control signal, could we  use for example something like an uln2003 to feed the max4051 I/O pin?

arduino pwm output 5v--- uln2003 12v--- Max4051 I/O pin 3?

Thanks
F

[Reply #6 on:]

Just a crude switching in of resistors will only work if you are after a potential divider which in the case of some of your pots you are not.
Most digital pots are 5V
http://en.wikipedia.org/wiki/Digital_potentiometer
but this is the only one I know that will work up to +/- 16V
http://uk.farnell.com/analog-devices/ad5293bruz-20/ic-dig-pot-1024pos-20k-14tssop/dp/1827274

[Reply #7 on:]

Hi Mike,
Yes, In fact i was thinking of using this one:
http://www.analog.com/en/digital-to-analog-converters/digital-potentiometers/ad5290/products/product.html
with the arduino library:
http://www.arduino.cc/en/Tutorial/SPIDigitalPot
and the dip adapter:
http://www.epboard.com/eproducts/protoadapter.htm#TSSOPtoDIPAdapter

It will be an expensive solution ... but should work ...
F

[Reply #8 on:]

Yes that looks fine to me.