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The Equalizer

The Equalizer. Jeremiah Harmon Greg Buzulencia. Topics of Interest. Overall Design Description Component by Component Description Interface Description Design Issues Cost Estimates. Inspiration. Challenges facing cyclists today. Resistance Level: 4 Heart Rate: 95 bpm.

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The Equalizer

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  1. The Equalizer Jeremiah Harmon Greg Buzulencia

  2. Topics of Interest • Overall Design Description • Component by Component Description • Interface Description • Design Issues • Cost Estimates

  3. Inspiration • Challenges facing cyclists today

  4. Resistance Level: 4 Heart Rate: 95 bpm The Equalizer – Summary • Electromagnetic Bicycle Trainer system. • The resistance from 1-10 can be selected using push buttons connected to the HCS12.

  5. The Equalizer - Uses • Riding with others of varying skill. • A rider in a flat area can simulate hills. • Act as an indoor trainer. • Interfaced heart rate monitoring system.

  6. System Block Diagram 12V Battery 5V Supply Voltage to Current converter (DC) Magnetic Hysteresis Brake Micro-controller Heart rate sensor Push buttons LCD screen

  7. Full System Diagram

  8. The Equalizer - MCU to Brake • The brake is controlled by the HCS12 with a voltage-current converter. • The converter can apply a DC current to an electromagnetic brake. • An electromagnetic hysteresis rotary brake can provide resistance against the rear wheel of the bike.

  9. The Equalizer - Power • Since the bike is mobile, a lightweight 12V nickel metal-hydride rechargeable battery is used. • Power is supplied to brake (primarily), MCU and device controller. • Considerations are being taken for issues dealing with bursts of current drawn by brake.

  10. Electromagnetic Brake • Applies a constant resistance against rotation of rear wheel of the bike. • Can increase the amount of power a user needs to exert on the bike by 5-40%. • The user can pick from 11 levels of resistance. • Each level provides preset resistance.

  11. Electromagnetic Brake – Overview • A Magnetic Hysteresis Brake best met our project design constraints. • The hysteresis effect. • Two components –a reticulated pole structure and a steel rotor/shaft assembly. • Ball bearing can spin freely without touching – no friction • Magnetizing force creates a flux field.

  12. Electromagnetic Brake – Overview • The rotor is magnetically restrained • Smooth, infinitely controllable torque loads • Torque independent of speed • Quiet operation • No wear components exist • Long, maintenance free life

  13. Electromagnetic Brake – Operational Specifications • High maximum operating speed. • The maximum rotational speed was calculated using a top road speed of 40 MPH. (40mi/h) * (5280 ft/mi) * (12 in/ft) * (1/60 hr/min) * (1/(26*) in-1) = 517 RPM • Given a 4” brake, the maximum RPM of the brake will be 3361 RPM.

  14. Resistance level Force (lbs) Torque on Wheel (in-lb) 0 0 0 1 .5 6.5 2 1 13 3 1.5 19.5 4 2 26 5 2.5 32.5 6 3 39 7 3.5 45.5 8 4 52 9 4.5 58.5 10 5 65 Electromagnetic Brake – Operational Specifications Resistance conversion table: brake torque vs total force.

  15. Electromagnetic Brake - Schematic

  16. Electromagnetic Brake – Operating Limitations

  17. Rear view of brake system

  18. Battery • The largest power consumer is the Magtrol HB-8-3 brake which uses 15 Watts to power itself. • Maximum current draw from the brake, assuming a top speed of 40 mph, is 750 mA. • At maximum speed (3400 RPM) for 3 hours: 3hrs x 750 mA = 2250 mAh • Other components draw an additional 50mA. • Total: 3hrs x 800mA = 2400 mAh

  19. Power Consumption Problem • When the brake has a sudden current draw, power could be drawn away from other components. • Solution: Add capacitors to maintain voltage.

  20. Nominal Voltage Minimum charging time Minimum Life Cycles Standard charging time Capacity 12 V 1.2 hours 500 14 – 16 hours 1800mAh Battery - Operational Specifications

  21. Heart Rate Monitor • Heart rate monitor must be accurate but un-cumbersome for the user. • The ideal solution: not connected to user accurate can remain with the bike when not in use. • Requirements met by the Salutron Model 4000. Two electrical contacts determine the user’s EKG.

  22. Heart Rate Monitor • Stainless steel contacts are durable and weather-proof • Simplified wiring • The sensor is recreational, not medical, with a tolerance of 0.65%.

  23. HR Monitor - Specifications • Salutron Model 4000 • Power: 3 volts (+/- 10%) @ 2.2 mA maximum • PCB Dimensions: 1.6 x 0.75 x 0.4 inches (41 x 19 x 10 mm) • Input signals: Right and Left sensors, Vcc and Ground. • Output signals(TTL compatible): • 1.      One pulse signal per each detected heartbeat • 2.      UART serial port: heart rate reported at each heart beat • 3.      SPI serial port: heart rate or ECG waveform reported

  24. HR and LCD Mount Diagram

  25. LCD Display • The LCD displays the current heart rate and resistance • The center button turns the resistance on and off • The user can scroll through modes by pressing the ‘Enter’ button and the ‘up’ or ‘down’ button • The users are defined by going to the user mode and selecting <New User> from the list of users

  26. LCD – Operational Specifications • Okaya RC2004LRSASOK • Vdd = 2.7v – 5.5v max • Max Temperature = 70ºC • Min Temperature = -20ºC • Display Dimensions: 76 mm x 25.2 mm • Display Characteristics: 20 characters x 4 lines • LCD Controller: Samsung KS0066U LSI

  27. Resistance Level: 4 Heart Rate: 95 bpm LCD Diagram

  28. Device Controller • Device controller takes PWM signal from HCS12 and outputs a linearly equivalent current to the electro-magnetic brake

  29. Device Controller - Specifications • LORD Rheonetic Wonderbox Device Controller Kit (RD-3002-03) • Power: 12 Vdc (2 A max output) • Size: 3.5 x 2.5 x 1.1 inches • Input: 2.1 mm Female banana plug • PWM: 30 KHz unfiltered ( input )

  30. Interface to HCS12 • The HCS12 must have sufficient I/O interfaces for the sensors and controllers. Heart Rate Sensor: serial connection LCD: 13 parallel bits Brake Controller: PWM output Push Buttons: 3 timer ports • These ports are all available on the HCS12

  31. Interface Diagram HCS12 Brake Controller PWM A SER1 B P2 P1 P0 PWM SPI R L CR DB CMD Heart Rate Monitor Buttons LCD

  32. Component Product Quantity Item Cost Total cost to us Brake Magtrol HB-8-3 1 $174.95 $174.95 Push Buttons GC Electronics 3 $3.78 $11.34 LCD Display Okaya RC2004LRSASOK 1 $25.80 $0 (Donated) Battery w/ solder tabs Dantona DANAA1800MMHWT 10 $3.50 $35.00 50 pin connectors Philmore 70-4250 2 $1.78 $3.56 Device controller LORD RD-3002-03 1 $170.00 $170.00 Microcontroller with Evaluation Board Technological Arts Adapt9S12E256 with Motorola MC9S12DP256D 1 $133.00 $0 Heart Rate Monitor Salutron 1 $25.95 $25.95 Total $579.60 $420.80 Cost Estimates

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