Well, the prototype I built a couple of weeks ago now is semi working. I haven’t been game enough to remove the resistor limiting the current completely but have reduced its value once and may experiment with reducing it further after the next circuit change. The video below shows the circuit before I disassembled it:

The circuit featured in the video is comprised of a Microchip Dual Channel 12-bit DAC (MCP4922) controlled via SPI, a Current Sense amplifier (TS1102-25), a Microchip Quad op-amp (MCP6L04T) and a generic NPN transistor (C9014). One of the problems not mentioned in the video is that when I got the Current Sense Amplifier, I miscalculated which gain I needed, so the amplification is not high enough for the circuit to work as desired. The solution to the problem is to use the op-amp in the circuit and ditch the current sense amplifier completely, which also has an added bonus of reducing cost and reducing the number of unique components.

I’m currently working on implementing the new circuit and testing it out. I should have an update on what the end electronic structure will look like tomorrow including some of what hasn’t been tested and discussed.