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

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

3. 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

4. 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

5. Overview

6. 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

7. 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

8. Budget Estimate
Items
Price
Quantity
Cost
Op-amp chip
$1.38(for ) 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.

9. Projected Schedule

10. Questions?