Most standard 60HZ AC motors come in approximately 3600 RPM or 1800 RPM. The barrel sander needs to spin at about 30 RPM. To achieve this, the following approximate pulley sizes will be used:
- 1800 RPM motor
- Shaft to 2″ Pulley
- Belt to 7.5″ pulley
- Shaft to 1.75″ pulley
- Belt to barrel (approx 23″)
- End Result is approx 30 RPM
(This was from memory so might be fractionally off).
Here is a render of the pulley assembly (draft):
Well, the fun is increasing with Arduino. We hooked up some circuitry which enables a transistor to switch a fairly large 12V load via a very small 5V digital pin on the Arduino board.
This has been a great learning resource: http://www.kpsec.freeuk.com/trancirc.htm
Basically, we have 12V power going through a motor circuit (protected by a signal diode), and then to the collector of a transistor. The emitter of the transister is connected to ground.
Lastly, the Arduino ground is joined with the emitter, and the transistor is switched by a 5V digital output pin on the Arduino board.
Now, just need to find something useful to do!