Closed Loop Current Sensor Design Project Team Ben

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

Problem Statement � To work with Allegro Micro. Systems 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 $1. 38(for 100 -499) 1 $1. 38 10 k Resistors 1/4 watt(pack of 5) $1. 19 4 $4. 76 Toroid Gap Core $5. 00 1 $5. 00 Magnet Wire 18 AWG, 200 ft $15. 12 1 $15. 12 Allegro current sensor A 1362 $3. 28 1 $3. 28 Op-amp chip Total $29. 54 *Allegro Microsystems Inc. is providing the funding for this project.

Projected Schedule

Questions?