W.I.N.C.

1
W.I.N.C. s Smart Controller

• EE 4522 Senior Design II
• Department of Electrical and Computer Engineering
• February 25, 2002
• Preliminary Packaging Review

2
W.I.N.C. Team
Dr. J.W. Bruce, Faculty Advisor
Tim Willis, Team Leader
Michael Nestler

• Naquisha Causey

3
Technical Challenges

• Programming Microcontroller
• Switching Mechanism
• Digital Signal Interfacing
• Power Consumption

4
Microcontroller Challenges

• Time- Behind Schedule
• Software Development The Chip is activating
  loads at the appropriate time, but
• stopping them too early.
• Test runs show variant time delays.

5
Alternatives for Switching Mechanism

• WINC explored various alternatives for switching
  mechanism before making a final decision.
• Both electromechanical relays and solid-state
  relays had rewards, and drawbacks.

6
AC Load Circuit using EMR
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Switching Circuit

• nMOSFET (enhancement)
• (ID17A ,VGS100V)
• Diode
• (1 Watt, 100V)
• Resistor
• (1 Watt, 10 ohms)
• Relay
• (High Capacity, SPST-NO)

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(ID) Relay on with MOSFET off
Induced Current Vg 0V
9
(ID) Relay off
MOSFET On
10
Suppresses excessive voltage change in the load

• Excessive volt change occurs in short time
• Used to protect the SSR and EMR
• Photo coupler traduces electrical to optical
  signal and relay signal through space.

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AC Load Circuit using SSR

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Trade-offs b/t SSR and EMR
SSR
EMR
Pros Pros
Longer Operating Life High isolation between outputs
High Input-Output isolation Low cost per contact
High resistance to shock Very low on-resistance (10 m? )
No sparking Lower Output Capacitance (1pF)
Cons Cons
Heat Sink required Greater Weight
Higher price per contact Shorter Operating Life
Higher on Resistance (100 ?) Lower shock and vibration Resistance
Higher output capacitance (20pF) Switching-induced EMI
13
Switching Mechanism

• Electromechanical Relays
• The relays were selected based upon Lifespan
  10,000,000 cycle operations Affordability
  16.53/ea. Vs. 3.02/ea.

www.Omron.com
www.Magnecraft.com
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Digital Signal Interface

• (2) Thermistors(s)
• Use one MAX1618 thermistors that uses a
  transistor for remote temperature detection.
• Reduce to 1 to conserve the maximum power
  constraint and the software memory space

1
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Signal Flow of the Thermistors
3904 Location In Bottom of Drain Pump
MCU
A/D Converter
output
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Power Distribution
With One Thermistor (mW) With Two Thermistors (mW)
MCU (Ubicom) 700 700
A/D Converter (Max 127) 1074 1074
Thermistors (Max 1618) 444 888
TOTAL 2218 2662
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Power Consumption (one thermistors)
18
Power Consumption w/ two thermistors
19
Physical Packaging of PCB

• 2 Printed Circuit Board(s)- (Schematics)
• User Interface Switches and LCD (Top)
• HVAC--Mechanical Loads/ Software
• Chips (Inside plastic covering in
• door)

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PCB Layout
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Manufacturability of Design

• - Surface Mount instead of thru hole.
  Significantly reduce the cost of production.
• - Availability and affordability of SSR for
  design application of switching Mechanism.
• Build professional relationships with
  distributors
• Research the reputation, and longevity of the
  manufacturer for components

22
Mechanical Load Test
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Acknowledgements
Special Thanks Extended to -MSU Faculty Dr. J.
W. Bruce, Dr. R. Winton, Dr. Harden, and Dr.
Joe Picone MSU Faculty -Viking Range, Inc
Mr. John Picardat Engineer, Mr. Martin
Wesemann General Manager, Ms. Beth Williams-
Assist. Product Manager - Rep. Inc. Mr. Jason
Shoemake- Sales Engineer
24
Hardware Prototype (Before)
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PCB (After)

• COMING SOON!!!!!!!!!

26
Q/A Session
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Switching Circuit (Relays)
Armature off
Armature on
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AC Loads

• 1. Heater
• 2. Circulation Pump
• 3. Drain Pump
• 4. Dispenser
• 5. Inlet Valve
• 6. Exhaust Fan

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Circuit Protection (diode)
Snubber
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Microcontroller
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Smart Controller is Managed by the Ubicom SX28

• Internal clock register/counter
• 20 I/O pins
• Configure I/O pin-by-pin
• Sleep/Wake up pin
• Provide software upgrades quickly
• User Configurable speeds

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Why Ubicom?

• 20 I/O Pins, exactly fulfilling requirements
• 136 Bytes of memory
• Family of chips

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Chip Pin Assignments
1 SX28 28 2
27 3
26 4
25 5
24 6
23 7 22 8
21 9
20 10
19 11
18 12
17 13
16 14 15

• RTCC MCLR
• VDD OSC1
• n.c. OSC2
• Vss LCD 0
• n.c. LCD 1
• Door LCD 2
• i2c (data) LCD 3
• i2c (clock) LCD 4
• Rinse Aid LCD 5
• Button0 Drain Pump 0
• Button1 Drain Pump 1
• Button2 Circ. Pump
• Button3 Heater
• Inlet/Fill Fan

34
LCD Display (from Optrex)
Communicates digitally with the microprocessor
through 6 separate data lines. Displays 24
characters total.
35
Load Characteristics
36
User Interface Flowchart
37
Hardware Interface
38
I2c, and why?

• I2c is a method of placing multiple digital
  devices, called slaves on a single 2-wire bus.
  
• A master device can access any of these slaves
  via serial communication. (ie, bit-by-bit.)
• Conserves I/O pins at the cost of speed.
• Our thermostats are placed on an i2c bus.

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But Wait! How is an analog signal on an i2c bus?

• We are using an ADC to convert the one analog
  signal to a 12-bit digital number.
• The ADC is i2c compatible, and has multiple
  channels (for more than one analog input).

40
Timeline
41
MAX1618
42
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44
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7 Alan T. McDonald, Stephen H. Frisked, David
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45
REFERENCES-(4)
10 T. Erickson, Turbidity Sensing as a
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Industry Applications Magazine, Vol.3, No. 3, pp.
31-36, May-June 1997. 11 J.W. Bruce,
Microprocessors II, Mississippi State
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Rexford, Electrical Control for Machines, 5th
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