motor speed sensing by eric hall. problem overview
Post on 23-Jan-2016
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Motor Speed SensingMotor Speed Sensing
By Eric HallBy Eric Hall
Problem OverviewProblem Overview
Problem Overview Problem Overview (cont.)(cont.)
• Router will cut the stock material
• Router uses induction motor
• Constant bit speed and RPM required
SolutionSolution
• Closed loop micro-controlled systemClosed loop micro-controlled system• Router bit RPM sensorRouter bit RPM sensor
Which Sensing Which Sensing Method?Method?
Methods considered:Methods considered:• Frequency to VoltageFrequency to Voltage• ShuntShunt• Hall EffectHall Effect• InductiveInductive
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
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
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
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.
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
Inductive Current Inductive Current SensingSensing
Inductive current Inductive current sensors work sensors work similarly to Hall similarly to Hall Effect current Effect current sensorssensors
Inductive VS Hall Inductive VS Hall EffectEffect
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
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
QuestionsQuestions
Any questions should be asked Any questions should be asked now.now.
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.