This board is a simple carrier for Allegro's ±5A ACS714 Hall effect-based linear current sensor. This version accepts a bidirectional current input with a magnitude up to 5 A. The output is an analog voltage (185 mV/A) centered at 2.5 V with a typical error of less than 1.5%.
We recommend careful reading of the ACS714 datasheet (661k pdf) before using this product. The sensor operates at 5 V and has an output sensitivity of 185 mV/A. The following list details some of the sensor's key features:
The pads are labeled on the bottom silkscreen, as shown in the picture to the right. The silkscreen also shows the direction that is interpreted as positive current flow via the +i arrow.
We sell a 30A unidirectional version and ±30A bidirectional version version of this board; you can distinguish these versions by reading the text on the IC or by looking at the color of the X on the bottom silkscreen. This version is marked with a blue X.
The sensor requires a supply voltage of 4.5 – 5.5 V to be connected across the Vcc and GND pads, which are labeled on the bottom silkscreen. The sensor outputs an analog voltage that is linearly proportional to the input current. This output voltage is centered at 2.5 V and changes by 185 mV per amp of input current, with positive current increasing the output voltage and negative current decreasing the output voltage.
The input current can be connected to the board in a variety of ways. For low-current applications, you can solder 0.1 "male header pins to the board via the small through-holes on the input-current side of the board. For higher-current applications, you can solder wires directly to the through-holes whose sizes best match your wires, or you can use solderless ring terminal connectors, as shown in the picture to the right. The large through-holes are big enough for #6 screws.
The board has two mounting holes on the logic side of the board. These mounting holes are 0.5" apart and are designed for #2 screws.
The IC has an internal filter resistance of 1.7 kΩ, and the carrier board includes a 1 nF filter capacitor, which produces a low-pass RC filter with a 90 kHz cutoff. You can improve sensing system accuracy for low-frequency sensing applictations by adding a capacitor in parallel with the integrated 1 nF capacitor across the pads marked “filter" on the bottom silkscreen (this capacitor is labeled C2b in the schematic below). The frequency F that the filter will attenuate to half its original power is given by:
F = 1 / (2πRC) = 1 / (11kΩ * (1 nF + Cf))
where Cf is the value of the capacitor added to the filter pads.
Pololu ACS714/ACS715 current sensor carrier schematic diagram.