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Thread: ACS711 current sensor

  1. #1
    Senior Member
    Join Date
    Aug 2016

    ACS711 current sensor

    I want to use acs711,i have connected the gnd of the sensor with the agnd of the microcontroller to filter the "noise", i have connected still a 1nf capacitor between analog pin and ground.
    I searched the internet and saw this kit where it drives the analog signal of the sensor to an LM358 and an MCP3221. So you can pass the signal either through the a / d converter or the amplifier.
    I filtering the "noise" by connecting the sensor to the analog grounding of the microcontroller will I get relatively good measurements or it is deemed necessary the output signal to pass it by an amplifier or a / d converter for correct measurements?


  2. #2
    Senior Member brtaylor's Avatar
    Join Date
    Mar 2016
    Portland, OR
    Completely depends on what your requirements are. We don't know the accuracy that you need to measure current or the expected current range. The click board isn't doing anything magical - it's simply buffering the sensor output and measuring with an ADC. You could also buffer the sensor output before bringing to the Teensy ADC or you could go for a non-unity gain if your expected current is very low. Hard to tell with the information given.

  3. #3
    Senior Member
    Join Date
    Nov 2015
    Cold hollow VT
    ISTR the ACS711 is a 5v device and 0amps is an output of 2.5v with maximum (positive) current translating to about 5v. The Teensy can only tolerate 3.3v max on the analog input, so it has to be scaled with a resistor divider and (perhaps) followed by a buffer to lower its impedance for sending into the Teensy analog inputs. Since the sensor output has an offset (now scaled), your Teensy code would have to take that into account to provide the correct sign/magnitude answer.

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