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Adding Voltages?

Discussion in 'General Electronics Discussion' started by hpfiend, May 8, 2013.

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  1. hpfiend


    Feb 20, 2013
    Hello all!

    I am having a hard time understanding what is going on in this circuit I am probing.

    I have two wires hooked to a motor that have varied pwm output with hall sensor input.

    I T-tapped both wires in parallel and determined the following with my multimeter.

    The hall sensor goes from low signal to threshold point to high signal

    Wire A hooked to + on multimeter and - multimeter probe to ground shows 10 volts DC at low hall sensor signal and 60% duty cycle at about 1 kHz. As the hall sensor signal increases to threshold the voltage and duty cycle increase to 14 volts and 94%. At the threshold point the pwm turns off and the wire maintains 14 volts at the high hall sensor signal.

    Wire B is the inverse. Hooked to + on multimeter and - multimeter probe to ground shows steady 14 volts at low hall sensor signal. At hall sensor threshold the pwm turns on at 1kHz and 94% duty cycle. At increasing high hall sensor signal the voltage decreases from 14-10 volts DC and the duty cycle reduces to 60%.

    Now- what I can't figure out is if I hook Wire A to + and Wire B to - on my multimeter, I get the following.

    At low hall sensor signal I get negative -4 volts DC and the same 60% duty cycle. The duty cycle increases to 94% as it approaches hall sensor threshold and the voltage reduces to negative millivolts. At hall sensor threshold the circuit reverses polarity and shows positive millivolts and 6% duty cycle. At high hall sensor signal the duty cycle increases with positive voltage, I am assuming it will go to positive 4 volts and 40% thought I have not witnessed this yet.

    This should be obvious but it is escaping me....

    Thanks for any help you may be able to offer!!!!
  2. duke37


    Jan 9, 2011
    I am sorry but I cannot understand your description. Please sketch a circuit diagram, scan it and post it.

    What is a Hall sensor threshold?
    What does the motor do?
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