Another project I’ve been working on this summer while stuck not in my lab was an inexpensive dual peristaltic pump design. It consists of two 12 Volt peristaltic pumps from Adafruit along with a Metro (Adafruit’s Arduino clone) as the brain.
There’s nothing special about the design. Half of a dual H-bridge is used to power the two pumps (each draw ~ 250 mA) and PWM is provided by the Arduino. I read the value of the two potentiometers to adjust the pump speed. Since I’m only using one side of the H-bridge and 2 of the six PWM-able pins on the Arduino, I should be able to double the number of pumps in this design, should I feel so inclined.
Right now, I get 14 to 56 mL/min out of the pumps with fairly good linearity. To test it, I grabbed the serial command parser from my OMIS syringe pump so I could control flow rates from the Arduino Serial monitor (on a Raspberry Pi, of course). Here’s a plot of flow rate as a function of PWM value. Note that I have the H-bridge in an inverted configuration, so a PWM value of 0 is 100% duty cycle. Also, on the Arduino, 255 would be 0% duty cycle.
Flow rates were calculated by measuring the mass of water delivered in 60 seconds and assuming a density of 1.00 g/mL for water. Reproducibility is also reasonable, with % RSD of the average flow rate (n = 3) being 2% or less with no obvious duty-cycle dependence. It is unclear to me why one pump delivers slightly more fluid than the other, and I’ll have to try the other 2-3 motors I have lying around my office to see if it is due to the motor or something subtle about the circuit.
As I mentioned earlier, I had to do this at home during the summer since I wasn’t allowed in my lab to do research. Plus, I had my 3D printer at home and worked on building a case for the pump. Sure, it looks like just a box, but I’ve been learning how to create finger-joints in CAD software so I can easily migrate the design to wood or PVC sheets on the CNC-mill. In any case, I had to do the testing in my kitchen, and I don’t have a good set of volumetric glassware in my kitchen, so I used what I had.