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

The Equalizer – Summary

Electromagnetic Bicycle Trainer system. The resistance from 1-10 can be selected

using push buttons connected to the HCS12.

Resistance Level: 4

Heart Rate: 95 bpm

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.

System Block Diagram

LCD screen

12V Battery

Micro-controller

Voltage to Current

converter (DC)

Magnetic Hysteresis

BrakeHeart rate

sensor

Push buttons

5V Supply

      

 

 

  

Full System Diagram

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.

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.

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.

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.

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

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.

Electromagnetic Brake – Operational Specifications

Resistance conversion table: brake torque vs total force.

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 - Schematic

Electromagnetic Brake – Operating Limitations

Model RPM VDC Resistance Acceleration Weight Continuous Power Diameter

HB-2.5 20,000 12 36 Ohms 41,100 rad/s2 .24 lbs 5 Watts 1.25 in

HB-8 20,000 12 45 Ohms 15,200 rad/s2 .49 lbs 15 Watts 1.8 in

HB-16 20,000 12 32 Ohms 17,900 rad/s2 .65 lbs 20 Watts 1.97 in

Rear view of brake system

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

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.

Battery - Operational Specifications

Nominal Voltage

Minimum charging time

Minimum Life Cycles

Standard charging time

Capacity

12 V 1.2 hours 500 14 – 16 hours

1800mAh

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.

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%.

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

HR and LCD Mount Diagram

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

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

LCD Diagram

Resistance Level: 4

Heart Rate: 95 bpm

Device Controller

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

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 )

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

Interface Diagram

HCS12

LCDButtonsHeart Rate

Monitor

SER1

SPI R L CR

B

A

P2 P1 P0

DB CMD

Brake Controller

PWM

PWM

Cost Estimates

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

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