I am building one of these for a physics demonstration (This part shows him test

Question

I am building one of these for a physics demonstration (This part shows him testing the prototype which resembles what I am making, feel free to watch part one and other parts to see exactly how it's made)

http://youtu.be/9BDKe358mtY

How can I effectively estimate the Voltage and Current given the RPM of my motor after it is built? How would I go through calculating it?

If someone can calculate it out for me, that would be great! Because I am stuck. I don't even know everything I need to keep track of while building the generator.

Explanation / Answer

Kv - RPM Constant

The higher the voltage, the faster a motor spins. The Kv rating designates the RPM a motor will spin at full throttle when unloaded given an input voltage. To estimate the RPM of a motor, simply multiply the Kv value by the battery voltage. Kv is in units of RPM/Volt.

RPM= Kv * Voltage

Kt - Torque Constant

The more torque a motor needs to produce, the more current it will draw. The Kt rating designates the amount of torque a motor will produce given a current. To estimate the torque of a motor, simply multiply the Kt value by current. Kt is in units of Inch*Ounce/Amp.

Torque = Kt * I

However, usually you will need to find out how much current the motor will draw based on a torque. The equation then becomes

I = Torque / Kt

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