Specific objective

Estimate the torque of an unknown motor.

Assignment development

Component: Jameco Metal Geared Motor without encoder

Usually this motors came with a downloadable datasheet in the jameco web site, but for some reason this is not the case, perhaps it’s just too old and jameco put it out of sales. However we need to know the torque it’s capable of deliver.

What’s known?

Usually this motors work within 6-12 volts of direct current range.

Electric Diagram

Just needed to wire the motor to the power supply with the reference value of 12 Volts.

Measured Data

This is a screen shot of the power supply in our lab.

V=12 [volts]

A = 0.06[Amp]

P=0.720 [Watt]

Estimating RPM’s

We need to apply the following formula in order to determine the torque:

𝜏=  (974 𝑃)/𝑛

Where:

𝜏=Torque [Kgf∗m]

P=Power [Kw]

n=Revolution per minute [RPM]

But we do not know the RPM value yet, so with a chronometer and the power supply synchronized together we counted the revolutions in one minute and determined:

𝑛=150 [𝑅𝑃𝑀]

Applying the formula

τ=  974 P/n

τ=  (974 (0.000720Kw))/150 RPM

τ=0.0046752Kgf*m

τ=4.6752grf*m

Therefore this is by no means able to lift a load bigger than 4.6 gr in a 1 metre lever.