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Experiments and Applications

Stan's information about his project
How to measure motor parameters
List of experiments and applications

In my science fair project I conducted many experiments with these electric motors.

In my first year I compared my original reed switch motor to the conventional motor from a toy car. The results were favorable but they cannot be considered accurate because these motors were too different: they required different voltages, contained different amounts and types of wire, the magnets were not the same, etc.

In the third year of my research I compared several different motors sharing the same unified mechanical design. The results of this comparison were very accurate and reliable.

One of the manipulated variables in the experiments was voltage.

The independent variables were the number of magnets on the rotor, the sensor position, and weights in torque testing.

The dependent variables were the speed, measured in revolutions per minute; and the relative power, measured as an angle on the torque testing device, or as the weight, lifted with the help of a speed reducer.

The consumed electric power (in Watts) was calculated as the power supply voltage (in Volts) multiplied by total current through the circuit (in Amperes).

After building the motors I noticed that the spinning magnets on the rotor could be used for calculating the speed in revolutions per minute. To assist in finding the rpm value I used another reed switch. The signals from the second reed switch were sent to specially built 3-digit electronic decade counter. Last year I improved this counter replacing the reed switch with a Hall effect switch and adding an extra decade for easier measurements.

One of the big challenges was the torque measurement. Torque, the twisting force of a motor, is a very important characteristic. As this task is quite complicated it was decided to measure a relative power as an angle on a specially designed device. It is shown on the picture below.

Torque tester

In torque experiments one end of the string (heavy-duty thread) was taped to the axle, and the other end was attached to the top of a lever. The bottom end of the lever served as a pointer showing the angle on the dial. A lath was attached to the pointer end. Several holes in the lath were used for adding heavy bolts and nuts as weights to increase the lever resistance.

The spinning rotor of the motor was winding the string around the axle. The string was long enough to allow the motor to gain full speed before pulling the lever. The maximum angle was noted.

The actual torque was not calculated. However, the angle measurements provided very reliable results for relative power comparison, as the motor with higher torque will turn the lever to a larger angle.

Last year, for torque measurement, the motor was attached to a speed reducer. One end of the piece of thread was affixed to the axle of the speed reducer, while the other end contained a hook, which was holding a box. As the motor spun, the thread was slowly winding onto an axle. This lifted the box. The speed reducer ratio was approximately 1:150, which means that the motor needed to make 150 revolutions to make the axle rotate one turn. The box that was lifted contained a specific number of weights, which were actually ceramic tiles. Three ceramic tiles weighed exactly 1 lb. To achieve 0.5 lb. increments, one tile was split in half. The picture below shows also a regulated power supply (in the upper right corner) and the electronic counter (on the right side).

Experiment with weight lifting

Some of the motors were powerful enough to lift up to 4 kg (9 lbs) on 6V. The speed reducer increased the power of the motors, but decreased their speed significantly.

Project CD available at the ordering page contains full information about my experiments including all graphs, tables, etc.

It is very easy to measure electrical parameters of the motors.

This is how you can measure voltage:

Voltage measurement

This is how you can measure current:

Current measurement

To measure voltage, current and other electrical parameters you need a multimeter. It should be able to measure currents up to 2 A or higher. A good digital multimeter is available at our ordering page.

You can calculate the consumed power of the motor by multiplying current and voltage.

One of the more difficult tasks is the speed measurement. The electronic counter Stan used in his project is a complicated device and can be recommended to experienced users only. The principles of its operation are briefly described in Forrest Mims book on "Digital Logic Circuits" (see Links section). We added a similar RPM counter to the list of our products. You may buy a kit and assemble it yourself or order preassembled ready to use device.

There are some other suggestions we received from our customers that may be used for the speed measurement.

Mark Seale suggested to use a strobe light (stroboscope) to determine RPM. Many strobe lights have active counters showing the flash rate. Brad Higgins used a bicycle counter. Optical tachometers may be used to determine spin rate, however they require a propeller attached to the motor which may slow it down. Frequency may be measured to calculate the speed. Or just attach a string with a small weight and measure with stop watch the time needed to lift the weight the certain distance (this method is good only for a relative comparison).

Here is a summary of the experiments you may conduct with these motors:

Additional experiments:

You may find a lot of useful information on the Project CD (available at the ordering page) which contains full information about my project.

Possible applications:

If you have any ideas for other experiments or applications please email us – the best suggestions will be published on this page.

If you do some of the above this electric motor may not only serve as a model but as a good science fair project.