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Rev 2 - W2021 Farris Matar

Rev 2 - W2021 Farris Matar

Apr 20, 2021

Hall Effect Current Sensor Board

The Hall Effect Current Sensor board uses a hall effect current sensor to measure the current flowing through the arm motors, ensuring the current doesn't go too high to avoid damaging the components. The board receives 5V power from the power distribution board to power the IC's.

The hall effect current sensor is an IC that can measure the current flowing through a wire or plate without touching it. This is done by measuring the magnetic field produced by the current being measured and translating it into a voltage reading.

Calculations

According to the Melexis Reference Design Guide for Current Sensors, the magnetic field produced by the current can be estimated using the following equation:

The HECS board uses the following parameters:

  • Trace width of 3.175mm

  • Vertical position of 1.55mm

  • Current ranging from 0 to 30A.

Using the equation above:

  • B (mT) = (1.25 / 12.55) * I, where I is the current in Amps

  • For I = 0 to 30A, B = 0 to 2.988mT

The resulting voltage from the magnetic field depends on the sensitivity of the current sensor. The sensor currently being used has a programmable sensitivity between 100mV/mT and 700mV/mT, with a typical value of 250mV/mT. The sensitivity can be calibrated using the sensor's test pin. Assuming the typical value for the sensitivity:

  • V (mV) = 250mV/mT * B

  • For B = 0 to 2.988mT, V = 0 to 747mV

Changelog

  • Replaced screw terminal connections for SPI and power with a 5 pin molex connector

  • Replaced old current sensor (MLX91205KDC-AAL-003-RE) with new one (MLX91208LDC-CAL-000-TU)

  • Changed all passive components to 0603

  • Reduced size of the board

Current Sensor

Project Documents

Designers

  • Farris Matar - Schematic Capture and PCB design - far-mat42

Built With