need programmable resistor

[Admin]

I was tasked with putting together 24 potentiostats (programmable resistors) to control voltages across 24 'magic batteries'. This is one single system - not independent systems.

These 'magic batteries' (I can't talk about them) have an optimal voltage, yet the voltage changes given environmental influences, so they must be shorted with a resistor to keep the voltage constant.

The typical resistance required is under 100 ohms.

I have a list of ideas on how to do this, but they are all over-complex and not very scalable . . . so I'm looking for other ideas from anyone familiar with potentiostats.


edit: a scientist on my team decided < 100 ohms is better

[waltr]

I'm thinking of a MOSFET, variable resistance, controlled with a feed-back circuit.
How much current does the "<100 Ohm resistor" need to pass?

[Admin]

The MOSFET + resistor idea was the first thing I thought of, but having 24 of them doing this at the same time makes it challenging. More importantly, it really complicates current measurement when it's an on/off PWM (I forgot to mention that current must also be measured). The scientists on the project don't [yet] know what a PWM'd short, or capacitors, would do to the batteries.

How much current does the "<100 Ohm resistor" need to pass?

Current varies, but it'll be under 100mA.

[Soeren]

Hi,

These 'magic batteries' (I can't talk about them) have an optimal voltage, yet the voltage changes given environmental influences, so they must be shorted with a resistor to keep the voltage constant.

The typical resistance required is under 100 ohms.

A MOSFET controlled by a high gain rail-rail op-amp, where the the battery voltage is compared to a reference voltage would be able to keep the voltage pretty constant.
If a power op-amp is used, the MOSFET isn't needed.
This will be linear (i.e. not on/off or PWM but a linear).

What voltage is available to run the circuit?