Enrichment Program

Summer School

Contact Us


Mechatronics Learning Studio


Power DynoTorque


  Maxime Lepage, Samuel Leblanc-Robert, Marc Myre, Dept of Mechanical Engineering, University of Ottawa


Safety instructions


In general

1)      Read these instructions

2)      Keep these instructions

3)      Beware of all warning

4)      Follow all instructions

5)      Do not use apparatus near water

6)      To reduce the risk of electric shock, do not expose this apparatus to rain or moisture


Concerning the power supply

1)      The power supply unit can be operated in an ambient temperature from 5oC up to 40oC max

2)      Do not give too much power to a small resistance. A small resistance receiving too much power can overheat and cause minor burns.

3)      Do not simultaneously touch the positive and the negative terminal of the power supply. This can cause an electric shock.


Concerning the Laser

1)      Always keep in mind that a misuse laser can be dangerous

2)      Do not point a laser into eyes.




Material Needed for the Experiment


?  12 V DC motor

?  Photo-electric cell

?  10 kΩ resistor

?  9 V battery

?  Coupler

?  Mounting base for the motors

?  Spring with a known constant

?  Frequency counter

?  Multimeters

?  Ohm ranger

?  Power supply

?  Breadboard

?  Various wires

?  Tape


Connection of the Multimeters and the Frenquency Counter

V: voltmeter

A: ammeter

1.      Calculate the input voltage and current and the output voltage and current.

2.      Measure the frequency through the Photocell.



Calculate the Frequency (rpm) of the Motor


1. Once the ammeters, voltmeters and frequency counter are connected properly, you have to connect the 9V battery to the circuit.

2. Connect the power supply to the motor.

3. Use the black coupler to couple the generator to the motor you want to evaluate.

4. Turn the ammeters, voltmeters, the frequency counter, the power supply and the laser ON.

5. Provide the circuit with approximately 10V and 300 mA.

6. Use the Ohm Ranger to do at least 5 tests using 5 different resistors.

7. Write down the data which are Vin, Ain, Vout, Aout, Resistance and the Frequency for every tests.


Note:  The frequency will be given in Hz by the frequency counter. Use this formula to convert it in RPM

X  Hz  *  60 (secondes/min) *  2π (rad/ rotation) =  Y  RPM



Calculate the Torque of the Motor (with a Spring)


1.      Once you have calculated the frequency, leave only the ammeter that displays the input current.

2.      Separate the generator from the motor you are testing.

3.      Attach the non-elastic wire to the shaft.

4.      Do 5 tests with 5 different input currents (constant input voltage) and write down the elongation of the spring for all 5 tests.

(Do not set up Vin to high!)








The photocell circuit is not responding

-          Test the 9V battery with a multimeter.

If less than 3v are measured, change the battery   for a new one.


The frequency counter displays inconsistent values

-          Verify the connection of the photocell circuit.

-          Make sure that there is no change in ambient light during the test.


The motor is not working

-          Test the motor with another power supply.

-          Buy a new motor ( The one used may have overheated)


Smoke is coming from the resistance

-          Lowering the power supply of the motor or use a larger resistance


Inconsistent values at the output of the generator

-          Use single resistance instead of the OhmRanger



The movement of the spring is jerky when testing the torque                                                        

-          Use a spring with a smaller constant of elasticity