motor

Seth's Electro-Piston motor

version 1
This is an electric piston motor I made to avoid studying for finals. like a car engine, it has a piston, connecting rod, and flywheel. In an internal combustion engine, the force to move the piston comes from burning gas, while in this motor the piston is moved by an electromagnet (solenoid coil from something or other). the arc you see is from commutation - i.e., the switching on and off of power to the coil. when power is applied to the coil, it pulls the 'piston' into its hollow center (opposite from a gas engine which can only push). obviously, for the motor to spin, the coil must be switched off for half of the rotation (when the piston is being pulled back out of the coil by the momentum of the flywheel). I switched power to the coil by putting scotch tape around a little bit > 180 degrees of a convenient rotating metal surface (in this case, the flywheel). as the motor rotates, the tape alternately blocks and permits current flow to the coil. the flywheel is an old VCR head motor and doesn't have anything to do with making the motor spin. although it's hard to see, there is a wire connecting the body of the flywheel mount to the coil (no current goes through the connecting rod, it's made out of cardboard).

version 2
ok, I had another final to avoid studying for, so I modified my ghetto duct tape-cardboard motor to have electronic commutation (instead of mechanical on the original motor). say goodby to that lovely arc :-(. Like the first version, we still need to switch power to the coil on and off depending on shaft position. SO, for the new version I made a sensor out of an infrared LED and a phototransistor. The LED shines IR light on a shiny part of the flywheel and the phototransistor receives the reflected IR from the LED. Like before with the scotch tape breaking electrical connection, here I used electrical tape to make half of the flywheel non-reflective. Thus as the motor spins the phototransistor turns on and off as it alternately receives IR and no IR. I breadboarded up a circuit to switch power to the coil through a FET, controlled by the optical sensor. The result is a sort of brushless DC motor! Pretty slick, eh?

version 3
I took a couple of hours and mounted the motor on a piece of wood and soldered the circuitry onto a little piece of perfboard. This version works pretty well and even has speed control!

videos!

first version, not much duct tape	it works!	second version, much more duct tape and electronic commutation control!
the IR shiny surface detector	green LED for a shiny surface...	...and red for the electrical tape
the third version is mounted on a piece of wood (stronger that duct tape and I get my desk back)		the cardboard connecting rod has been replaced with a metal one and the coil can be adjusted by loosening the two screws clamping it down
the circuitry is built onto one board using almost all salvaged parts...	...with a speed control! damn it gets hot.	the homebrew IR position sensor

videos

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