vikash23
Full Member level 2
Hi,
Please see the attached schematic,
I am using a motor drive to drive a brushed DC motor clockwise and anticlockwise using complementary PWM
I am using a current sensor ACS724LLCTR-05-AB to measure the current of the motor while running
I am measuring using ADC output and the datasheet of the sensor says the sensitivity of the sensor is 400mV/A
So when no current flows through the current sensor the output voltage of ADC is 2.5V. The ADC value that I measure is 512 (0 - 1023 range)
I apply a small load to the motor of around 100mA and I see the ADC voltage rises to 460(Approx) from 512.
Subtracting the ADC value I get 52 ADC value and multiplying by 4.88mV (5V system) 253.76mV
If I divide 253.76mV / 400mV I get 0.633A
My motor max current rating is only 0.8A and I apply only a small amount of load which is 0.1A. I see 0.633A which I dont understand.
When I say 0.1A I measure it via my external power supply.
Is it because the current via motor is switching(20KHz) I am doing a wrong calculation in measuring the output current.?
How do I do the calculation.
Is it something to do with RMS value?
Please see the attached schematic,
I am using a motor drive to drive a brushed DC motor clockwise and anticlockwise using complementary PWM
I am using a current sensor ACS724LLCTR-05-AB to measure the current of the motor while running
I am measuring using ADC output and the datasheet of the sensor says the sensitivity of the sensor is 400mV/A
So when no current flows through the current sensor the output voltage of ADC is 2.5V. The ADC value that I measure is 512 (0 - 1023 range)
I apply a small load to the motor of around 100mA and I see the ADC voltage rises to 460(Approx) from 512.
Subtracting the ADC value I get 52 ADC value and multiplying by 4.88mV (5V system) 253.76mV
If I divide 253.76mV / 400mV I get 0.633A
My motor max current rating is only 0.8A and I apply only a small amount of load which is 0.1A. I see 0.633A which I dont understand.
When I say 0.1A I measure it via my external power supply.
Is it because the current via motor is switching(20KHz) I am doing a wrong calculation in measuring the output current.?
How do I do the calculation.
Is it something to do with RMS value?