Computer controlled potential difference across wires

Question

I am trying to design a circuit to control the potential difference across 2 stainless steel wires. The two wires are connected together at one end (common node) and on the other end, one wire is connected to +ve and the other wire is connected to -ve. With a DC bench power supply, I performed a voltage sweep from 0V to 20V, with a maximum of 200mA of current drawn by the wires @ 20V. I would like to replace the DC bench power supply with a computer-controlled alternative.

My question is, how to use a simple Arduino microcontroller to do so, my main issue is how to convert the simple PWM single and amplify it to a voltage range of 0 to 20V, taking into account the current requirement of 200mA. One idea is to connect the PWM to a low pass filter, basically extract the DC element, followed by using an opamp to amplify the signal. Can anyone advise me on what would be the best approach ?

I attached a sketch of the wire setup.

Answer 1

The total resistance for 200 mA at 20V is 100 Ohm. The wires should be quite long or thin.

But as answer: I guess you want to make some kind of heating. If you plan PWM control, high enough switching frequency should quarantee the temperature of the wire stays in certain range, no matter the current is alternating being part of the time 0 mA and the rest of the time 200 mA. Heat capacity and heat transfer calculations are medium complex and they are impossible without knowing better your actual system.

The guess can be wrong. If the current should stay in certain DC value you can well have an inductor, switching transistor and a flyback diode. Have high enough inductance to keep L/R much bigger than the switching period. You can find the needed inductance by simulating if you cannot do elementary time constant calculations. the Starting point is to decide how much the current is allowed to swing.