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Author Topic: replace a variable resistor digitally?  (Read 7741 times)

trials_modder

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replace a variable resistor digitally?
« on: August 08, 2007, 12:28:39 AM »

hi,

i want to make this pulse width modulation circuit http://www.eleinmec.com/article.asp?28 as it will provide the features needed to drive my motor. however, this circuit is adjusted using a potentiometer, but i'd like to control it by circuitry and avoid doing so mechanically. any ideas?

thanks
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Re: replace a variable resistor digitally?
« Reply #1 on: August 08, 2007, 08:26:20 AM »

Maxim has digital pots here:

http://www.maxim-ic.com/products/digi_pot/

I have requested a sample from them before and they gave me two.  I was supposed to play with them but I never really got the time (I was planning on designing a software/hardware controllable fanbus).
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trials_modder

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Re: replace a variable resistor digitally?
« Reply #2 on: August 08, 2007, 06:08:27 PM »

do you have any idea what that variable resistor is equivalent to? i didn't know these digital potentiometers existed, and there seems to be a broad selection of types and "taps". also, how are these controlled in the circuit?
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Re: replace a variable resistor digitally?
« Reply #3 on: August 09, 2007, 10:23:47 AM »

I forgot what model I got but I believe you would need a non-volatile linear taper one.  As for the Taps, I'm thinking the more taps it has, the more values your resistor can output.  like say, you have a 10 ohm, 10 tap resistor.  you can set your resistance from 0 to 1, 1 to 2, 9 to 10.  My guess is that you can't set it to 1.5 or anything in between 1 and 2 ohms.  I could be wrong.
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trials_modder

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Re: replace a variable resistor digitally?
« Reply #4 on: August 09, 2007, 07:11:30 PM »

ok, and how do i go about setting that resistor value in my circuit? i guess it depends on whatever type of non-volatile chip it is?
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