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  • Current sensor for DC motor

    mibawad

    Member

    Updated: Oct 25, 2024
    Views: 2.3K
    Hello All,
    I am looking for current sensor to measure the consumed current by DC motor by using data acquisition card. I was thinking to use small resistance or Hall effect current sensor. My motor details are:
    Nominal voltage= 42V,
    Starting current = 20.3A
    max. continuous current = 1.95A

    The data acquisition card acquires max. voltage for +/-10V

    My question are:
    1- What is the best (using small resistance or using hall effect current sensor)?
    2- Should I consider that maximum current is the starting current or max. continuous current before selecting the sensor?

    Many thanks.
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  • jjdraw

    Member • Jan 24, 2011

    small resistor.
    calculate resistor watt rating too.
    could use op-amp for pre-scaling when using very small resistor.
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  • freak16

    Member • Jan 25, 2011

    Could anybody tell me what is hall effect current sensor?
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  • sasuke

    Member • Jan 25, 2011

    i guess the hall efect sensor is such as curent transformer. It isolated between primary & secondary. Primary side will be high current while secondary will be low/bias current. When current go trough primary, the magnectic fluc will genarated and bias the secondary side. This secondary side will energize as a data (ADC value as set from MCU).

    If use this current transformer, the max current motor (starting current need to consider) must suitable with primary side of current transformer spec.

    about your question:
    1. i choose small resistor as sensor. This design normally use amplifier to gain the current. The advantages for me is easy for change amplifier gain of the motor current. But you need to calculate the watage of the resistor can suport the motor current (starting current)

    2. the max current should starting current. Just take care of resistor watt rating.
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  • mibawad

    Member • Jan 26, 2011

    Many thanks for your answers. However, I am using PWM driver to drive the motor. Does this affect of the reading of the resistor? I mean the reading of voltage in resistance will be also PWM and the current will be PWM also.
    Best wishes,
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  • freak16

    Member • Jan 26, 2011

    thanks a lot!
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  • jjdraw

    Member • Jan 26, 2011

    mibawad
    Many thanks for your answers. However, I am using PWM driver to drive the motor. Does this affect of the reading of the resistor? I mean the reading of voltage in resistance will be also PWM and the current will be PWM also.
    Best wishes,
    yup, should get PWM voltage reading as long as you 'read' the value fast enough.
    Also, you might try to use a FET with low RDSon as your sense resistor if you cannot get a resistor of proper watt rating.
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