variable resistance controlled by voltage - Electronic Circuits Projects Diagrams Free

pigrider · 8th June 2007, 11:04 PM

the idea is very simple. i have a sequencer that puts out 0-10 volts. i would like this sequencer to control a machine with potentiometer knobs. so variable volts controlling variable resistance. the volts are already there i just need a circuit to replace the knobs/pots.

any help would be greatly appreciated. my electronics knowledge is very limited so please explain thoroughly.

Hero999 · 8th June 2007, 11:14 PM

The answer to your problem is not that simple.

You could have a servo connected to a pot or go for the electrical approach.

I got as far as designing the block diagram for an electronic load resistor by using an analogue multiplier configured as a divider connected to a MOSFET. The divider monitors the voltage and current across the divider and adjusts the gate voltage to keep the resistance constant, i.e R=V/I.

What value resistor do you require?

What does the potentiometer control?

It's probably easier to integrate the control directly into the maching rather than using an electronic pot.

You can buy digital pots but I don't think they would be any use here as you want it to be voltage controlled.

pigrider · 8th June 2007, 11:51 PM

the pots are on a reel to reel machine that plays music. i dont know the resistances off hand but can get them if it would help.

pigrider · 9th June 2007, 12:06 AM

would some sort of 'digital volume control' be a good replacement for these pots?

dknguyen · 9th June 2007, 12:13 AM

No, those pots respond to SPI signals or some other digital signals...not analog ones. Sounds like the circuitry inside an RC servo is similar to what you need (the way it works). I suppose you could just use a uC with an ADC to read the voltage and then control a digital pot...but that seems to not be as simple as you want.

Russlk · 10th June 2007, 01:24 AM

If the pots that you want to replace are volume controls, then a digital volume control would be the ideal. You just have to convert the voltage to a digital signal with an A/D.

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8th June 2007, 11:04 PM	(permalink)
pigrider	variable resistance controlled by voltage the idea is very simple. i have a sequencer that puts out 0-10 volts. i would like this sequencer to control a machine with potentiometer knobs. so variable volts controlling variable resistance. the volts are already there i just need a circuit to replace the knobs/pots. any help would be greatly appreciated. my electronics knowledge is very limited so please explain thoroughly.

8th June 2007, 11:14 PM	(permalink)
Hero999	The answer to your problem is not that simple. You could have a servo connected to a pot or go for the electrical approach. I got as far as designing the block diagram for an electronic load resistor by using an analogue multiplier configured as a divider connected to a MOSFET. The divider monitors the voltage and current across the divider and adjusts the gate voltage to keep the resistance constant, i.e R=V/I. What value resistor do you require? What does the potentiometer control? It's probably easier to integrate the control directly into the maching rather than using an electronic pot. You can buy digital pots but I don't think they would be any use here as you want it to be voltage controlled. __________________ I also post at the following sites: http://www.stop-microsoft.org http://www.heated-debates.com Screen name: Aloone_Jonez And http://www.silicontronics.com, same screen name as here.

8th June 2007, 11:51 PM	(permalink)
pigrider	variable resistance controlled by voltage the pots are on a reel to reel machine that plays music. i dont know the resistances off hand but can get them if it would help.

9th June 2007, 12:06 AM	(permalink)
pigrider	variable resistance controlled by voltage would some sort of 'digital volume control' be a good replacement for these pots?

9th June 2007, 12:13 AM	(permalink)
dknguyen	No, those pots respond to SPI signals or some other digital signals...not analog ones. Sounds like the circuitry inside an RC servo is similar to what you need (the way it works). I suppose you could just use a uC with an ADC to read the voltage and then control a digital pot...but that seems to not be as simple as you want.

10th June 2007, 01:24 AM	(permalink)
Russlk	If the pots that you want to replace are volume controls, then a digital volume control would be the ideal. You just have to convert the voltage to a digital signal with an A/D. __________________ see my website: www.geocities.com/russlk