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a turntable embedded on a PCB, a silkscreen on a round PCB to encode the position using gray code
tools used
Layout
a few approaches on the hookup
Gray code
“to get a gray number only change one bit”
components
other methods
LED as light Sensor
no word regarding detection speed
magnetic
DC motor
simply connecting a dc motor to the spinning disk
by rotating the disk you convert the energy to analog input for MCU or whatever
problem with this approach it will not give enough output at slow speeds. so probably scratch that.
Stepper motor
same as with the DC motor, you connect the motor to the disks center, then hook the stepper winding A1/2,B1/2 to an MCU, you get a nice stepping encoder.
following links are actually to use the sinusoidal wave of the stepper, a bit of a different approach
also a problem at low speeds.
