1. Assignment#01: Literature Survey on Sensors and Actuators ECE5320 Mechatronics Assignment#01: Literature Survey on Sensors and Actuators Topic: Hall Effect Sensor Prepared by: Steven Swenson Dept. of Electrical and Computer Engineering Utah State University stev.swen@aggiemail.usu.edu 435-227-5498 3/9/2012

2. 5/1/2015 ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators Slide-2 Outline –Reference list –Operational Concepts –Major applications –Major specifications –Limitations –A typical sample configuration in application –And many more relevant issues in applications (such as, how to choose, cost information, where to buy etc.)

3. 5/1/2015 ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators Slide-3 Reference list http://www.youtube.com/watch?v=9BFdGtvo9JE –Switch, latch, ratio metric sensor http://www.wellsve.com/sft503/Counterpoint3_1. pdfhttp://www.wellsve.com/sft503/Counterpoint3_1. pdf http://en.wikipedia.org/wiki/Hall_effect_sensor http://www.youtube.com/watch?v=04Nb8QXthM whttp://www.youtube.com/watch?v=04Nb8QXthM w http://www.youtube.com/watch?v=ntWJIlKc2PQ http://www.sensorland.com/PDF/allegrotp002.pdf

4. Operational Concepts At its core, a Hall Effect sensor can detect the presence of a magnetic field. When it senses a field, it can do one of three things: –Switch on or off –Latch on or off –Output a voltage proportional to the field encountered 5/1/2015 ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators Slide-4

5. Operational Concepts, Cont. Switch –Possibly the most common use for the Hall Effect –Does just what the name suggests: the sensor switches on or off depending on the presence of a magnetic field –Can be configured to trigger on a North or South pole field –When a field is detected, it outputs a high signal –When no field is detected, it outputs a low signal –Additional logic can swap signals 5/1/2015 ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators Slide-5

6. 5/1/2015 ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators Slide-6 -The switch activates upon the presence of an electric field http://upload.wikimedia.org/wikipedia/commons/7/7e/Hall_sensor_tach.gif

7. Operational Concepts, Cont. Latch –Uses a magnetic field to switch on (North or South) –Uses the reverse pole to switch off Example: A South pole field activates the latch, and a high is output. The output remains high until a North pole field activates the latch, at which point the output is pulled low. 5/1/2015 ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators Slide-7

8. 5/1/2015 ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators Slide-8 -The output is latched high for a (usually) South magnetic field, and pulled low for a North magnetic field

9. Operational Concepts, Cont. Proportional Voltage –Does not use any ‘switching’ logic –Output from Hall Effect Sensor is simply amplified –Useful for determining the strength or polarity of a magnet 5/1/2015 ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators Slide-9

10. 5/1/2015 ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators Slide-10 -The output of the sensor is proportional to the proximity of the magnetic field

11. Major Applications In short, anyplace where electrical contact is not practical but position determines output –Measuring the speed of a rotating tire –Determining the position of a motor shaft –Door/Window is open or shut –Laptop lid is closed or open 5/1/2015 ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators Slide-11

12. Major Applications, Cont. –Cell phone (slider or clamshell style) is open or closed –Magnetic Compass –Current through a conductor –Automotive Ignition and Fuel Injection 5/1/2015 ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators Slide-12

13. Major Specifications Most Hall Effect Sensors have 3 pins –Vs Supply Voltage –QOutput –GNDGround Current use is very small –Typically in the range of 20-30 mA –Must be amplified to be used 5/1/2015 ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators Slide-13

14. Limitations Because the Hall Effect relies wholly upon magnetic fields: –Stray fields from nearby conductors or magnets can cause a misfire of signal –Fields from magnets required for sensing may cause interference to nearby electronics –Output from sensor is often very small (milli-volts) and must be amplified before use This requires additional circuitry and power 5/1/2015 ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators Slide-14

15. Sample Application Hall Effect Sensors are used extensively in Brushless DC Motors 5/1/2015 ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators Slide-15 Hall Effect Sensors http://www.honeywell-sensor.com.cn/prodinfo/magnetic_position/technical/chapter7.pdf

16. Sample Application, Cont. Since Brushless motors are by definition contact- less, Hall Effect Sensors are used extensively –For a Brushless motor to accurately start up and move accurately, the exact position of the shaft must be known to the controller –The Hall Effect allows the position of the magnets inside the motor to be known –From this, the position of the shaft can be interpolated 5/1/2015 ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators Slide-16

17. Sample Application, Cont. –By knowing the position of the shaft, the controller knows what coil is in position to produce torque –After this coil is fired, the permanent magnets within the motor will move with the shaft –As these magnets move, the Hall Effect Sensors can see how fast and how far they have moved –This allows the controller to fire the next coil at the right moment to provide the required speed or torque 5/1/2015 ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators Slide-17

18. 5/1/2015 ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators Slide-18 To Explore Further Purchase –Hall Effect Sensors are widely available on the internet www.sparkfun.com www.mouser.com www.digikey.com –To name a few of many

19. To Explore Further, Cont. Sensors are commonly extremely small –Most are surface-mount They output very small voltages and currents –Additional circuitry is required for use in a modern processor 5/1/2015 ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators Slide-19

20. To Explore Further, Cont. Price Ranges –< $1 for simple switches and latches –> $50 for complex position sensing and harsh environments What to look for: –Output ranges Current Voltage –Output type Digital Vs. Analog 5/1/2015 ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators Slide-20

21. To Explore Further, Cont. –Type of Sensor Latch Switch Proximity –Sensitivity At what point will the logic do its job? 5/1/2015 ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators Slide-21