Product description: current sensor ACS709 -75A +75A - module Pololu
The module consists of a printed circuit board made for the system Allegro ACS709LLFTR-35BB-T. The sensor operates based on the Hall effect. The chip can be powered from a voltage in the range: 3 V to 5.5 V. Pin FAULT is by default in the high status. It reaches a low status when the value of the measured current exceeds the given threshold. The threshold value is selected by indicating the the appropriate voltage on the VOC pin. It depends on the values of the resistors of the voltage divider shown in the diagram below. By default, the threshold is set at 57 A but it can be changed by adding external resistor. Reset the error flag (low status) to FAULT pin through indicating the low status to the FAULT_EN pin (by default, it is pulled up to VCC). More details in the documentation.
The main characteristics of the current sensor ACS709 -75 to +75
- The system is optimized for current flowing in both directions from - 37,5 to 37,5 A with a linear measurement range from -75 to 75 A (please, pay attention to the heat limitations below).
- Due to the low resistance of the system (1.1m Om) and channeling, the power losses are very small.
- Through the use of Hall effect, the current paths are isolated from the logic part.
- The bandwidth is up to 120 kHz with the possibility of reduction by adding an additional condenser
- Precision of 2% at room temperature.
- Operating temperature: -40 °C to 150 °C.
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Maximum current is measured according to the duration of the measurement. For example, a current of 50 A can flow through the system for maximum, 20 seconds, without causing damage. After this time, the module reaches the temperature to above 150 °C. For the current above 30A, the manufacturer recommends to use the additional cooling. |
Pins of the ACS709 current sensor -75 to +75 A
For proper operation, to the sensor must be connected: the measured current (IP+ and IP-), supply voltage of 3V to 5.5 V (VCC and GND) and output (VIOUT). The remaining pins are not required, they are used to connect the external capacitors as was shown in the figure above.
The output voltage is proportional to the intensity of the measured current. The value is centered to VCC/2. During the power supply of the 5V, the output voltage changes to 28mV on 1A of the measured current. The positive direction of the current, increases the value of the voltage, the negative, on the contrary, decreases it. The pattern on the output voltage VOUT switches as follows:
VIOUT = (0.028 V/A * i + 2.5 V) * VCC / 5 V
Pin VZCR is the reference value of the voltage for zero current flow (0 A). This value is approximately equal to VCC/2, it allows to accurately calculate the intensity of the measured current.
Pin FILT allows you to connect an external capacitor Cf (between FILT and GND) which allows to limit the bandwidth, by default, set to 120kHz. More information about the external filtration, can be found in the system documentation.
Diagram of the module
Specification
- Supply voltage of the logic part: 3.0 V to 5.5 V
- Current consumption of the logic part: 11 mA
- Sensitivity for power supply of 3.3 V: 0,018 V/A
- Module weight: 1.7 g
- Dimensions: 21 x 23 mm
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