Closed Loop Current Sensor Design Project Team: Ben Briggs, Matt McCluskey Project Advisor: Dr. Kent Chamberlin

Problem Statement To work with Allegro MicroSystems to design a closed loop current sensor competitive response time balance between accuracy, speed, and cost

Background Hall Effect sensor IC Put in gap of c-shaped magnetic core Current through wire causes flux to flow around the wire Sensor IC reads magnitude of flux density Outputs a voltage proportional to flux passing orthogonally through it Voltage is proportional to current passing through wire

Error due to hysteresis of the core Fairly accurate and useful in some applications Feedback circuit introduced Coil wrapped around the core Magnetic flux on the core is canceled Greatly increased accuracy

Overview

Specific Design Objectives: To find a magnetic core that has low hysteresis properties at low levels of magnetic flux To design a controller that will predict the response of the hall effect sensor to lower the response time To design or find a current driver to take a voltage in and drive a current out to reduce magnetic flux on the core to zero To research viable methods for bidirectional current sensing To assemble a current sensor module and produce a reference design to be published on Allegro’s website

Testing Plan Test the response of the Hall Effect sensor IC when configured in the magnetic core Design a controller circuit based on the response of the sensor IC Test the output of the controller circuit to ensure correctness and find the amplitude of the voltage Design a current driver and determine the number of secondary windings on the core Build the current sensor module and test all of the components together Troubleshoot if complications occur

Budget Estimate Items Price Quantity Cost Op-amp chip $1.38(for 100-499) 1 $1.38 10k Resistors 1/4 watt(pack of 5) $1.19 4 $4.76 Toroid Gap Core $5.00 Magnet Wire 18AWG, 200ft $15.12 Allegro current sensor A1362 $3.28 Total   $29.54 *Allegro Microsystems Inc. is providing the funding for this project.

Projected Schedule

Questions?