motor speed sensing by eric hall. problem overview

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Motor Speed Sensing Motor Speed Sensing By Eric Hall By Eric Hall

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Page 1: Motor Speed Sensing By Eric Hall. Problem Overview

Motor Speed SensingMotor Speed Sensing

By Eric HallBy Eric Hall

Page 2: Motor Speed Sensing By Eric Hall. Problem Overview

Problem OverviewProblem Overview

Page 3: Motor Speed Sensing By Eric Hall. Problem Overview

Problem Overview Problem Overview (cont.)(cont.)

• Router will cut the stock material

• Router uses induction motor

• Constant bit speed and RPM required

Page 4: Motor Speed Sensing By Eric Hall. Problem Overview

SolutionSolution

• Closed loop micro-controlled systemClosed loop micro-controlled system• Router bit RPM sensorRouter bit RPM sensor

Page 5: Motor Speed Sensing By Eric Hall. Problem Overview

Which Sensing Which Sensing Method?Method?

Methods considered:Methods considered:• Frequency to VoltageFrequency to Voltage• ShuntShunt• Hall EffectHall Effect• InductiveInductive

Page 6: Motor Speed Sensing By Eric Hall. Problem Overview

Frequency to VoltageFrequency to Voltage

• RPM of Router Bit obtained directlyRPM of Router Bit obtained directly• Sensing material placed on motor axle Sensing material placed on motor axle • Sensor generates a pulse as it passes Sensor generates a pulse as it passes

materialmaterial

Page 7: Motor Speed Sensing By Eric Hall. Problem Overview

Frequency to Voltage Frequency to Voltage (cont.)(cont.)

• IC converts pulses IC converts pulses to frequencyto frequency

• Frequency is Frequency is converted to a converted to a voltage and sent voltage and sent to micro-controllerto micro-controller

Page 8: Motor Speed Sensing By Eric Hall. Problem Overview

Current Sensing Current Sensing DevicesDevices

• Detect the current Detect the current through the motor to through the motor to determine the motor’s determine the motor’s speedspeed

• When slip increases, When slip increases, current increases and current increases and speed decreases.speed decreases.

• Slip is the rotor falling Slip is the rotor falling behind the statorbehind the stator

Page 9: Motor Speed Sensing By Eric Hall. Problem Overview

Shunt Current SensingShunt Current Sensing

Measures current Measures current across a resistor across a resistor to find the to find the current through current through the motor.the motor.

Page 10: Motor Speed Sensing By Eric Hall. Problem Overview

Hall Effect Current Hall Effect Current SensingSensing

Hall Effect Hall Effect current sensors current sensors measure the measure the magnetic fields magnetic fields produced by the produced by the current in a current in a power power consuming wireconsuming wire

Page 11: Motor Speed Sensing By Eric Hall. Problem Overview

Inductive Current Inductive Current SensingSensing

Inductive current Inductive current sensors work sensors work similarly to Hall similarly to Hall Effect current Effect current sensorssensors

Page 12: Motor Speed Sensing By Eric Hall. Problem Overview

Inductive VS Hall Inductive VS Hall EffectEffect

Page 13: Motor Speed Sensing By Eric Hall. Problem Overview

ComparisonComparison

Sensing Sensing MethodMethod

CostCost Ease ofEase ofImplementatiImplementati

onon

DurabiliDurabilityty

SafetSafetyy

Freq. to Freq. to VoltageVoltage

$5$5 FairFair PoorPoor PoorPoor

ShuntShunt

SensorSensor$4$4 N/A (DC N/A (DC

Only)Only)N/AN/A N/AN/A

Hall Hall EffectEffect

$25$25 GoodGood GoodGood GoodGood

InductivInductive e CurrentCurrent

$20$20 GreatGreat GreatGreat GreatGreat

Page 14: Motor Speed Sensing By Eric Hall. Problem Overview

Final DecisionFinal Decision

After reviewing each of the After reviewing each of the methods for sensing current, I methods for sensing current, I determined that the only logical determined that the only logical choice was the inductive current choice was the inductive current sensing methodsensing method

Page 15: Motor Speed Sensing By Eric Hall. Problem Overview

QuestionsQuestions

Any questions should be asked Any questions should be asked now.now.

Page 16: Motor Speed Sensing By Eric Hall. Problem Overview

No Further QuestionsNo Further Questions

All questions should have been All questions should have been asked on the previous slide, as asked on the previous slide, as the presentation is now over.the presentation is now over.

No birds affected the sensors during the making of this presentation.