The circuit is adapted from previous projects. There is a raspberry pi connected to an atmega, with an op-amp for the pressure sensor, a simple motor driver, batteries and a 5v regulator. I've simplified the motor driver, so that it only passes current in one direction (the previous design had two push-pulls on each coil, which is unnecessary for just squeezing a pump chamber).

I learned one major lesson about driving coils from my last prototype. You must have two zener diodes in parallel to each coil, so that when you stop passes current through the coil, it does not burn out your circuit. When current stops, the magnet field that was created collapses and reverses voltage. This voltage will build until it can flow. If you have two zener diodes in opposite orientations in series with each other, and have them parallel to the coil, then you can provide a pathway for current to flow through the coil, and not through out your electronics :)