This week I led the stirring module group alongside Sungmoon, Alexander, and Sophia. I was inspired by the metal stir plates used in bio labs where magnets spin underneath and a stir bar magnet is placed in the solution to stir.
We started off with the cheap small dc motor connected directly to a 5V power supply. We mounted magnets with opposite polarity on right and left with tape and placed a stir bar in a cup with water to see if the motor could spin and handle the torque of the mounted items. This initial test worked, but sometimes the motor required an inital push to start spinning.
Video of magnet spin vortex here
Video of preliminary circuit test showing that motor can be programmed to spin with xiao signal pin to MOSFET gate here
We use one fast, low voltage DC motor to stir the magents and one slow, higher voltage DC motor to pull the magnets up and down by a spool. The stir bar is lowered into and raised out of the cup by a spool with dental floss attached to the stir bar.
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I initially made a PCB with one mosfet per motor and one external power source for the higher voltage motor. However, I realized the spool needs to go bidirectionally which requires an H-bridge so I went back to redesign the PCB.
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I also wrote the .ino script to accpet tirgger signal and start a preprogrammed sequence
Image of bad soldered board Cable crimping on and on