How to emulate a variable resistor?

[blapcb]

I have a system where there is a regular potentiometer that has some defined resistance range (say 50 to 200 ohms). I would like to change that resistor with a circuit which I can electronically control and would simulate the resistance. Any idea how to go about this? Thanks!

 

[btbass]

Have you looked at digitally controlled pots?
Microchip have some.

 

[blapcb]

Have you looked at digitally controlled pots?
Microchip have some.

Yes, actually I am just looking in to that but from what I can see, they are all 1Kohm and above.... I need something say zero to 500 ohms. Also it would need to handle more current.

 

[TekUT]

Have you looked at digitally controlled pots?
Microchip have some.

Yes, actually I am just looking in to that but from what I can see, they are all 1Kohm and above.... I need something say zero to 500 ohms. Also it would need to handle more current.

You've to do an active load circuit, in a simple way you can use a MOSFET and make a feedback around it in order to make the MOSFET as a constant current sink, or constant voltage or constant power load or what you need a constat resistor, just control the voltage and the current over the MOSFET and make appropriate feedback. Of course with this system is easy to obtain a simple resistor with one pole connect to ground.

Bye
Pow

 

[btbass]

You can also buy motorised pots, they are used in audio amplifiers for remote control. But more expensive.
Depending on the resolution you require, you could also implement a switched resistor network.
Another thing to look at would be J-fets. They act like a voltage controlled resistor.

 

[blapcb]

Pardon my ignorance... but do you mean to use a MOSFET *and* a DigiPot? Or a MOSFET will replace that. If you could be so kind as to upload some type of circuit so I could learn I would really appreciate it.

Thanks

Have you looked at digitally controlled pots?
Microchip have some.

Yes, actually I am just looking in to that but from what I can see, they are all 1Kohm and above.... I need something say zero to 500 ohms. Also it would need to handle more current.

You've to do an active load circuit, in a simple way you can use a MOSFET and make a feedback around it in order to make the MOSFET as a constant current sink, or constant voltage or constant power load or what you need a constat resistor, just control the voltage and the current over the MOSFET and make appropriate feedback. Of course with this system is easy to obtain a simple resistor with one pole connect to ground.

Bye
Pow

 

[FvM]

Generally, there's a lot of electronical variable resistor circuits, with specific properties, each. Some options have been already mentioned. They are very different in terms of usable voltage range, signal and control bandwidth, linearity, precision, noise, power consumption. So I don't think it makes sense to suggest some more without a specification. Your previos specification is a bit scarce.

I need something say zero to 500 ohms. Also it would need to handle more current.