Software suggestions and requests

[CescoAiel]

Another comment on peristaltic pump accuracy: those driven by DC motors, rather than stepper motors, have gear trains to provide the necessary torque. The $12 pump I found on Amazon has a maximum rotor speed of 100 RPM, but the motor is rated at 5000 RPM (probably no-load speed), so I am guessing there's a planetary gear system between the motor and the pump. If there can be a sensor on the motor shaft, the precision of the pump output can be multiplied by the gear ratio. Assuming a gear ratio of 36:1, that would make the slice thickness accuracy much better. Given the torque load of the pump rotor, I expect the motor doesn't coast very long after the power is shut off, maybe one revolution or less. Instead of a sensor on the shaft, it may be possible to detect the motor armature transitions in the motor current or voltage. Depending on the number of segments in the armature, that would provide even greater precision.

True, but you'd still need to keep in mind the number of rollers squeezing the pump-tube and their relative position to the end of the housing (ie where it stops pinching and allows the tube to return to normal diameter)

[DoulosDS]

True, but you'd still need to keep in mind the number of rollers squeezing the pump-tube and their relative position to the end of the housing (ie where it stops pinching and allows the tube to return to normal diameter)

Right; the motor controller would just keep the pump stopping point from drifting or dithering. The pump would always turn an integer multiple of 1/n for n lobes. My idea of sensing the pump lobe position optically would allow too much slice-to-slice variation. If the armature modulation counter goes over the number of armature bars, the controller could report an error or even correct an error if somehow the motor revolution counter lost count.