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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