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92 Making Things Move

FIGURE 4-14 Measuring motor torque

5. Turn the luggage scale on if it’s digital.

6. Connect the end of a strap or hook to the screw as close to the screw head
as possible.

7. Power on your motor.

NOTE If you’re testing a motor for which you don’t have a data sheet, it’s
best to use a benchtop power supply so you can find out the acceptable
voltage range for your motor (see Chapter 5). Alternatively, you can try
batteries that add up to the voltage your motor needs. Six volts would be a
good guess for most small DC motors.

8. Your motor will try to turn, but the connection to the luggage scale will stop
it. Read the luggage scale as the motor is stalled like this, and record the
number. Do this quickly, before your motor heats up from working too hard!