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    • #8558

        Hi all,

        The Lectron motor can also be used as a generator !

        In fact, all simple motors with brushes can.

        Let’s do an experiment to study this phenomenon and build following circuit :

        Motor generator

        When finishing, adjust the meter needle with P1 to mid position (this is called nulling).

        Now, turn the motor shaft slowly till it “jumps” to a new position while observing the meter.

        If you turn the motor shaft again till it moves to the other position, observe the meter again.

        What did you notice ?

        Now, what would happen with the meter if we start rotating the motor shaft slowly and then faster ?

        What will happen to the meter if we reverse the motor motor, so that the DC connection is made and rotating the shaft ?

        A bit of explanation about the circuit :

        The rotor inside the motor has 2 coils. Each coil is connected to the outside via brushes.

        If we move the coil (rotating the shaft) inside the magnetic field, a small current is induced in the coil, thus creating a small voltage across the outside connections (1 DC and 1 AC connection).

        The very small voltage (about 180 mV) is not enough to create a clear meter reading, so we add an amplifier.

        This amplifier is build around T1.

        We need to bias T1 properly, so that the voltage at the collector is about 4,5 V.

        Therefore we use a 2,2 M Ohm resistor for biasing and add a 120 Ohm resistor at the Emitter.

        The meter can be set to a mid position with P1. This means that the negative terminal will have the same potential as the positive terminal, creating a 0 reading.

        This way we can observe the motor behaviour and obtain a clear meter reading.





      • #8563

          Hi Frank,

          Great use of the new motor and magnet set!  Unique and interesting experiment and demonstration.  Thanks so much!  Best, M.

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