peristaltic pump

A peristaltic pump which works best with the red thera tube or similar silicone tubing. It can be used to pump liquids and does also transport gases (blow bubbles). The NEMA17 stepper motor which rotates the rollers is driven by a 555 timer IC and an A4988 driver module on a little pcb (see schematic). The rotor is attached to the stepper motor with a spiraled lock that has recesses for a wrenchlike tool. That locking mechanism proofed to be appropriate with a reasonable runout and clamping force. Before tightning, a spacer tool is inserted between the base and the rotor_base so there is 2 mm clearance. The gap between the runway and the rotorcircle, where the tube is seated, can be adjusted and easily tightened with a wingnut. That is necessary to get a good sealing of the tube. In- and outlet have clamps in order to prevent the tube from slipping.
I used a stepper motor model 17HS4401, available at our local electronic store, that has a rated current of 1,7 A and phase resistance of