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Process Data from Current Sensor

nicoloquinte

Hello, im in a quandcopter project for a while now and I just figured out that I needed a current sensor on each Bldc Motor and one on the Geneal Battery Rail.

I wanted to go with a certain ACS712 "Fully Integrated, Hall Effect-Based Linear Current Sensor" but for that I need 5 ADC on my Microcontroller (ATSAM3X8E).

And, since I have 16 of them, thats ok !

 

But .... I dont know if I would use them :

  • I need a really precise data that I can look into later
  • I dont want noisy readouts ( 4x4A BLDCs + Buck converters + radio traciver ...)

 

should I use one ADC per Sensor, use the builts-in ADCs : that's enought, or dou you have any sugestions ?!

 

Thank you in advance

 

EDIT :

ok ... after checking the price, I dont know if thats really the component tha I need, if you know a cheaper one, that would be great !

  • I have recently used the ACS712 5A version and have a couple of higher current one, but I am concerned in the off the shelf version are a bit noisy. The chip is currently not recommended for new design, which suggests they will be discontinued. Looking at the manufacturers website there are some newer more precise version out there.

     

    Also depending on the amount of current you are drawing it is possible to place a simple voltage divider to reduce the output to suit a 3.3V ADC ref, although you will still need a 5V Vcc. The voltage divider method I used in a recent data-logger project and worked quite well.

  • in reply to waelect

    Thank you for answer

    I didn't thought about using a resistor based sensor because I'm using lipo batteries to power the motors so It's why I went for these sensors but since I'm also monitoring the battery voltages that's ok !

    But i dont think you can get an current se.sing with a voltage divider

     

    Nico

  • in reply to nicoloquinte

    The voltage divider was to use for the O/P of the ACS712 to knock down the 4.5/5V down to a lower voltage for the ADC. Even though it is noisy it is a very low cost solution. Just be mindful of the noise level. I had to add a filter on the output to reduce the noise.

  • I too have used the ACS712 to monitor current in a light fixture (sample A/C currents).  To address the noise and to get a full range output voltage into my ADC, I added an amplifier/filter stage to boost the signal, while eliminating some of the noise.  The ACS712 worked well, but being a Hall effect device, the current signal would often get overwhelmed by other sources of interference (Microwave oven), so in the end it proved to be a poor choice.  I wonder if some of your noise might be the magnetic field fluctuations of your motors?

     

    Good luck

    Gene 

  • in reply to genebren

    yeah. actually my bldc are generatin a lot of boise but,for example my antennas are enought away from them so their aren't a problem.

     

    therefore, I think i'll go with high precision resistors and 16 bit external Adcs

     

    thank you for sharing your experiences ! (i didn't knew that a microwave oven radiations could be that important.