april (13&14) 2015 engr b47 intro. to egr. & design lab #12 electric motor
TRANSCRIPT
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April (13&14) 2015
ENGR B47Intro. to Egr. & Design
Lab #12Electric Motor
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Schedule / Timing
• Week 11: Introduction, Groups, Delegation• Week 12: Motor Construction• Week 13: Motor Construction & Troubleshooting• Week 14: Troubleshooting & Data Collection• Week 15: Troubleshooting, PowerPoint, “Report”• Week 16 (Finals Week*): Presentations
* Presentations will take place on May 13 from 8:00 - 9:50 am
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Basics of Magnetism
[walk-through on whiteboard]
• Permanent magnets– Likes repel– Opposites attract– Draw “field lines” represent this behavior
• Electromagnets– Relationship between current & magnetic field– Straight wires and loops
Review
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Building a Motor
[walk-through on whiteboard]
• Permanent magnets– Two fixed on the outside– One rotating in the center
• Can get a “motor” to work for half a rotation
• “Flip a switch” and change the magnet?
Review
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Building a Motor
What would it look like?
Graphics from pcbheaven.comhttp://www.pcbheaven.com/wikipages/How_DC_Motors_Work/
Review
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Graphics from pcbheaven.comhttp://www.pcbheaven.com/wikipages/How_DC_Motors_Work/
Review
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How Get Current to Coils?
Graphics from pcbheaven.comhttp://www.pcbheaven.com/wikipages/How_DC_Motors_Work/
Review
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Graphics from pcbheaven.comhttp://www.pcbheaven.com/wikipages/How_DC_Motors_Work/
Review
![Page 9: April (13&14) 2015 ENGR B47 Intro. to Egr. & Design Lab #12 Electric Motor](https://reader035.vdocument.in/reader035/viewer/2022062421/56649da75503460f94a93352/html5/thumbnails/9.jpg)
Motor Project Goals
• Construct a motor• Characterize performance (worksheet coming)
– Speed vs. Torque curve– Power vs. Torque curve– Maximum Power calculation
• Create instruction manual– Audience is middle school students– Include assembly guide & component list– Step-by-step instructions (lots of pictures!)– Troubleshooting section
Review
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Grading Criteria
Motor Project is 20% of final grade (see syllabus)
• Performance of motor [25%]– Mostly concerned that it works– Little incentive to out-perform other groups– Data is critical
• Presentation [25%]• Instruction Manual [25%]• Peer Evaluation [25%]
Review
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To Do List for Today
• Double-check 1st Day Stuff– Exchange contact information– Make schedule to accomplish all tasks
• Continue Constructing Motor– Collect needed pieces from instructor– Starting winding– Start modifying housing– Cut spacer for commutator– Finish wiring– Test function with power source (see instructor)
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Motor Construction
General Guidelines• Building the Electromagnet
– Tape the lag screws to the axle– Wind the wire around the bolts– -Windings 4 layers thick– -Leave 6” tails– Test the Electromagnet
• Building Commutator– Building the Commutator– Affix foil tape to the dowel– -Leave ¼” gap between contacts– Place stripped ends of wire under foil tape– Break in foil must be perpendicular to
electromagnet
• “Each time the commutator hits the point where it flips the field in a two-pole motor, the commutator shorts out the battery (directly connects the positive and negative terminals) for a moment. This shorting wastes energy and drains the battery needlessly”
• Forming the Brushes– Try with thin brass sheet– - ¾” wide by 3” long– Wind around nail– Form it to shape shown
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Motor Assembly
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Characterizing Motor Power• See write-up posted on course website• Wind up known mass (provided by instructor)
– Calculate power and torque– Will need timer & tachometer (provided by instructor)– Run with DC power supply (provided by instructor)
• Ideally measurements @ multiple speeds (masses)• Plot data, include in final presentation• Talk to me before taking measurements
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Power: Watts (Newton·meters/second)Force: Newtons (kilogram·meters/second2)Height: metersTorque: Newton·metersRotational Speed: Revolutions/second (not RPM)
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Writing a User Manual
• What to include– Assembly instructions– Operation instructions– Troubleshooting guide
• Format– Step-by-step guide– Lots of pictures / diagrams*– Use plain language (understood by 10-14 year olds)– Probably 3-10 pages (based on font size, # images)– Fairly open-ended as far as style
(How many columns? How many steps? Which orders should I put in the required elements?)
14* Of major components or steps. These are for clarification
of the operation, not to prove to me you built it.