Transcript The Equalizer

The Equalizer
Jeremiah Harmon
Greg Buzulencia
Topics of Interest
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Overall Design Description
Component by Component Description
Interface Description
Design Issues
Cost Estimates
Inspiration
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Challenges
facing cyclists
today
The Equalizer – Summary
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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
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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
5V
Supply
Heart rate
sensor
Push
buttons
12V Battery
Microcontroller
LCD screen
Voltage to
Current
converter
(DC)
Magnetic
Hysteresis
Brake
Full System Diagram
The Equalizer - MCU to Brake
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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
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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
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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
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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
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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
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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
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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
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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
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When the brake has a
sudden current draw,
power could be drawn
away from other
components.
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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
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Heart rate monitor must be accurate but uncumbersome 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
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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
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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
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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
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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
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Device controller
takes PWM signal
from HCS12 and
outputs a linearly
equivalent current to
the electro-magnetic
brake
Device Controller - Specifications
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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
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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
PWM
Brake
Controller
SPI
Heart Rate
Monitor
HCS12
SER1
P2
PWM
R
L
Buttons
A
CR
P1
B
P0
DB
CMD
LCD
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
50 pin
connectors
Device
controller
Microcontroller
with Evaluation
Board
Heart Rate
Monitor
Dantona
DANAA1800MMHWT
Philmore 70-4250
10
$3.50
$35.00
2
$1.78
$3.56
LORD RD-3002-03
1
$170.00
$170.00
Technological Arts
Adapt9S12E256 with
Motorola MC9S12DP256D
Salutron
1
$133.00
$0
1
$25.95
$25.95
Total
$579.60
$420.80
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