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The Smart Kegerator
EE-595
Group 1
Brandon Bartell
Nick
Sneha Juvekar
Anthony
Hector
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Members Here
Project: Smart Kegerator
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Refrigerating, dispensing, and monitoring device
for compressed fluids
Displays temperature
Displays liquid content
Prevents unauthorized usage
Project: Smart Kegerator
Project: Smart Kegerator
Temperature
sensor
Display
Signal Conditioner
Scale / Converter
Power Supply
Keypad/Security
Flow solenoid
Nick
Sneha
Hector
Anthony
Brandon
Performance Requirements

Keypad Matrix: 3 columns, 4 rows
Key Definitions: 0-9 digits, enter, clear

Sensory: Temperature and Weight

– Temperature accurate within 0.5 °C
– Weight Scale accurate within 0.8 lbs
Performance Requirements
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Power Modes: ON/OFF
Power Saving Modes: Standby
Standard Requirements
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Operating Temperature Range: 10°C to 32.22°C
Operating Humidity Range: 0-100% Non
condensing
Operating Altitude Range: -300ft to 15,000ft
Storage Temperature Range: -50°C to 65°C
Storage Humidity Range: 0-100% Non
condensing
Storage Pressure Range: 0.5 to 1.5 ATM
Sources: 120 VAC
Power Consumption: 74 W
Standard Requirements
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Volume: 17.6 ft3
Shipping Container Size: 31in.×68in.×28in.
Mass: fridge plus add-ons
Maximum Parts Count: 50 parts
Maximum Unique Parts Count: 20 parts
Full Warranty Period: 1 years
Service Strategy: Field Repair or Dispose
Product Life: 20 years or more
Key Technical Risk & Problem Areas

These are some key technical risks that we believe
might hamper our overall efforts
– Sensor interfacing
– Programming language selection - integration
– Potential long lead time on various components
– Size of prototype (transportation, work –space
availability)
– Component response to low temperatures
– Power supply interfacing (step-down transformers,
AC\DC conversion)
– Signal control and processing
– Microcontroller limitations
– High costs of components and supplies
EMC Standards
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IEC 6100-3-3: Limitation of voltage fluctuations and
flicker in low-voltage supplies <16A
– Required because a low end voltage flicker could
damage the compressor
IEC 6100-4-5: Surge Immunity tests
– Required because the microcontroller and other
components need to be protected from potential
power surges
IEC 6100-4-11: Voltage dips, short interruptions, and
variations
– Required because brown out conditions will affect
keypad thereby affecting overall performance
Safety Standards
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CSA C22.2 No. 14-95
– Applies for control and protective devices.
Control devices covered in this standard
include: pushbutton; flow-, pressure- operated
switches; and proximity switches.
IEC 60335-2-34
– Applies for the safety of motor-compressors,
their control and protection system which are
intended for household purposes.
UL 873
– Temperature-Indicating and -Regulating
Equipment: requirements for electrical
equipment for control for refrigeration
Specific Safety Requirements
 Ground
(GFCI)
Fault Circuit Interrupter
– Connected in series with the power
source. Needed because there will be
electronics in a potentially wet
environment: the sensors near the keg.
 Anti-tipping
Mercury Switch
– If the kegerator tips over, this will turn
off the compressor.
Example of Simple Gantt Chart showing
dependencies
Block Prototyping Plan Template
Block
Name
Block Area
(cm2)
Total PCB
Area
(cm2)
PCB
Substrate
Type
Comp
Attachment
Type
Socketed
Component
s
Types of
Connector
s
Nick
72
65
Plastic,
pads,
buses
Solder
Relay,
resistors,
LEDs
IEC,
Circular,
PCB
Mount
Hector
204
194
Plastic,
pads,
buses
Solder
Diodes,
resistors,
capacitors,
etc.
IEC, PCB
mount
Sneha
105
92
Plastic,
pads,
buses
Solder
ICs, LEDs
IEC, PCB
Mount
Anthony
81
66
Plastic,
pads,
buses
Solder
ICs, Relays
IEC,
Circular,
PCB
Mount
Brandon
112
101
Plastic,
pads,
buses
Solder
Diodes, IC,
resistors,
capacitors,
IEC
Block Prototyping Plan Template
 The
PCB will have pads and a bus
 All socketed components will be
soldered or din rail mounted
 All Connectors will be IEC, Circular,
or PCB mount.
 A minimum of 10 components will be
used by each block
Block Prototyping Plan Template
– Estimation Summary
 1277.8
Estimated vs 400 availability.
 $ 674.00 Estimated vs $600 available
investment
 3.29 % of total manpower for system
design tasks, detailed design tasks,
verification tasks, and documentation
tasks:
 Suggested down/up scope if needed:
Added CPLD Control, Electronic
Pressure Regulator, Volume/Flow
Control
Temperature Sensor Block
Owner: Anthony Futterer
The purpose of the temperature sensor is to monitor the temperature inside
the kegerator unit and serve to inform the user via the display block of the
temperature in degrees C.
Performance Requirements
• Accurate to 0.5 degrees C.
•Provide a user mountable probe device for internal placement.
• Provide an inline shielded signal cable for transmittance of the output
signal to the signal conditioner.
• Provide a separate signal conditioning circuit for output scaling to
suitable A/D converter range in display block.
Block Breakdown
4-30 VDC input from power supply
AD590
Temperature
Sensor Probe
Signal Conditioner
Interface with display
A/D converter
Block Detail Design
 AD590M
measures temperature in K
to 0.5 degrees accuracy.
 LM741 and LM1458 Dual Operational
Amplifiers serve as signal
amplification devices from uA to mA
needed.
 AD580 high precision voltage
comparator serves as error
correction tool.
Signal Conditioning Block
Owner: Anthony Futterer
The purpose of the signal conditioner is to convert the load cell output signal
to a usable A/D converter signal amplitude for the display block.
Performance Requirements
• Provide an input port for the signal from the load cell.
• Provide an inline shielded signal cable for transmittance of the output
signal to the display.
• Provide a separate signal conditioning circuit for output scaling to
suitable A/D converter range in display block.
Block Signal Table
Block Breakdown
24 VDC input from power supply
Load Cell
Input Connector
Signal Conditioning
Circuitry
Interface with display
A/D converter
Block Detail Design
 Takes
in Load Cell Signal.
 LM741 and LM1458 Dual Operational
Amplifiers serve as signal
amplification devices from uA to mA
needed.
 AD580 high precision voltage
comparator serves as error
correction tool.
Reliability Assessment, Growth
(Sig-Cond/Temp Sensor Block)
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The Team Used the Method B reliability
Database
Total from my combined blocks spreadsheet
was 343.2078566
Total MTBF was therefore 0.002393
The dominant parts of unreliability was the
MC1403U Precision Serial Voltage Reference
IC
This could be improved by using the AD580
Voltage Reference IC or a similar part with a
higher operating temperature than the
MC1403U.
Keypad Block
Owner: Brandon Bartell
•The main purpose of the keypad block is to provide a security feature by
making the user enter a 4digit-code. When the code is entered the user will
be allowed to pour their drink.
• Implementation of a controlling device will also provide metered pouring to
either 12 or 16 ounce depending on user selection.
Block Detail Design
Anticipated appearance of actual keypad
Block Breakdown
In from power supply block
Power
User interface (Keys)
Control/Timer
Interface with solenoid block
Out to solenoid block
Block to Block Interface
Power Signals
Power1 VCC +12
Digital Signals
Digital3 D9-D0
Type
Direction
DC Power Input
Type
Digital
Dir
Output
Voltage
Nominal
12.0V
Output
Structure
N/A
Voltage Range
Min
Max
9V
15V
Input
Tech
Structure
Standard TTL
Freq
Freq Range
Nominal
Min
Max
DC
0
N/A
% V-Reg V-Ripple Current
Max
Max
Max
10.00%
0.12V
40mA
Freq
Logic
Input Characteristics
Nominal Voltage Vih Min Iih Max ViL Max IiL Max
1.0Khz
5V
2.0V
60uA
0.8V
-1.2mA
Block Detail Design
 The
EEPROM memory protects the
stored data in case of power failure.
 Over 100 million combinations are
possible for the user codes.
 Two other codes can be used to allow
user to get a metered pour of 12 or
16 ounces.
 Two separate relay outputs.
 Audible key operation - optional
Performance requirements for
keypad block
Accuracy:
-Within .1% to .2%
User Indicators:
-Indicator Parameter: 3 LEDs.
-Applicable User Interface Type: Analog 3x4 keypad matrix
-Mechanical Interfaces: Interface with solenoid block via
relay signal.
-Analog Input Signal Frequency: 67Hz.
-Power Signal Input Frequency: 57 – 63Hz.
Standard requirements for keypad
block
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Min. Operational Ambient Temperature Range: 0
to 50 degree Celsius.
Min. Operational/Storage Ambient Humidity
Range: 100 %Rh.
Min. Storage Ambient Temperature Range: -50 to
65 degree Celsius.
Applicable Safety Standards: UL 873.
Applicable EMC Standards: IEC 61000-4-11.
Estimated Max. Production Lifetime: 5 years.
Reliability in MTBF: 0.09 years.
Service Strategy: Repair.
Safety requirements for keypad
block
 Compliance
 Compliance
 Compliance
 Compliance
 Compliance
with IEC61000-4-2
with IEC61000-4-3
with IEC61000-4-6
with IEC61000-4-8
CISPR11- RF Emissions
Block Detail Design
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Specifications
relay outputs:
– output 1: 5 Amp
– output 2: 1 Amp, N.C. & N.O. dry contacts, DC 30V
max.
operating voltage: DC 12V (DC 10-14V)
current drain: 10 - 100mA
duress output: NPN transistor with open collector output,
switches to ground (-) when activated, 100mA/25V DC
max.
codes available: User 1 & 2, Super User, Master, Duress and
Accelerated codes
code combinations: 111111100
dimensions: 4.6" x 2.9" x 1.9"
weight: ± 6.5oz (net), ± 8.1oz (gross)
Reliability Assessment,
Growth (Keypad Block)
 Total FIT’S = 825.2496
 MBTF = 0.00121175
 Dominant unreliable parts are LM741 Op-Amp and
Switches
 Obvious resolution for unreliable parts is to make
the switches waterproof as well as dustproof and of
a better quality to increase reliability factors as well
as better component selection on the Op-Amp.
Power Supply Block
Owner: Hector Gomez
The purpose of the power supply is to supply energy to all the blocks. It will
also provide overload protection in case of short circuit in the product.
Performance Requirements
• To deliver power at +/- 5% of required voltages with low noise.
•To supply enough current for all the blocks
• To turn off entire blocks with a toggle switch
Power Supply Block to Block
Interface
Block Breakdown
Temperature
sensor
Keypad/Security
120 AC
60HZ
Power Supply
AC/DC
120AC
5DC/24DC
3.0 Amp
Scale
Signal conditioner
Display
Hector
Flow solenoid
Block Detail Design
 Transformer
steps down voltage
 Diode Bridge does the conversion of
AC to DC Voltage with 3amps rated
diodes and 10% ripple
 First phase capacitor used to
eliminate transients and makes
voltage linear
 LM317T regulates voltage and offers
current limiting in case of failures in
the system.
Block Detail Design
 Specifications
 operating
voltage: 120VAC +/- 10%
 60 Hz Input +/- 3 Hz
 Output Voltage DC 5-12V
 Output Current 3A
 User Interfaces: Toggle switch (to
turn off power)
 dimensions: 8’’ X 10”
 weight: 18oz (net), ± 8.1oz (gross)
Basic Operation
•Transformer + Rectifier + Smoothing + Regulator
Transformer
turns ratio
=
V
p
Vs
=
N
p
Ns
Vp = primary (input) voltage
Np = number of turns on
primary coil
Ip = primary (input) current
power out = power
and in
Vs × Is = Vp × Ip
Vs = secondary (output) voltage
Ns = number of turns on
secondary coil
Is = secondary (output) current
Bridge Rectifier
Output with a Small Ripple
Complete Rectification
10% ripple, C= (5 X I) / Vs X f
C = smoothing capacitance in farads (F)
Io = output current from the supply in amps (A)
Vs = supply voltage in volts (V), this is the peak value of the unsmoothed DC
f = frequency of the AC supply in hertz (Hz)
Reliability Analysis of
Power Supply
 Total
FIT’S : 186.65.
 MTBF : 1/186.65= .005
 Dominant part for unreliability is the
switch with lambda = 44.
 Elimination of mechanical switch will
reduce considerable the lambda
factor.
Display Block
Owner: Sneha Juvekar
The purpose of the display block is to convert the analog
signal from the signal conditioning block to the digital
signal and to display either the temperature inside the
kegerator in degree Celsius or weight of the tank in
pounds on the 7 – segment LEDs and to eliminate the
switch bounce caused by user interface.
Performance Requirement for
Display

User Inputs:
-Input: 0 to 5VDC Analog signal from signal
conditioning block and 5 to 6VDC from power
supply.
-Indicator Viewing Environment: Bright light.
-Switch Type: SPST (Mechanical) Switch.
-Analog Input Signal Frequency: 67Hz.
-Analog Input Signal Impedance: 800ohms.
-Power Signal Input Frequency: 57 – 63Hz.
Performance Requirement for
Display

Accuracy:
-Within 1% to 5%

User Indicators:
-Indicator
Parameter: 4 7-segment LEDs.
-Binary Indicator Technology: LED.
-Analog Indicator Technology: Filament.
-Numeric Indicator Technology: 7–segment
LED.
-Applicable User Interface Type: Analog
Switch
-Mechanical Interfaces: PCB
Performance Requirement for
Display
•
Operation Modes:
- Applicable
-Functional
-Functional
-Functional
•
Power Input Type:DC.
Mode: Normal.
Features: Secure
Threshold voltage for a CMOS Hysteresis gate: 0.45 to
0.55V
Electrical Interfaces:
-Signal Type: Analog.
-Signal Direction: Input.
•
Mechanical Interfaces:
-Mechanical Interfaces: PCB.
•
Overall Product Association:
-Required to convert the analog signal into a readable measurement
of either Temperature or Weight.
Standard Requirement for Display
Max. Material Cost: $149.52
 Max. Manufacturing Cost: $22.50
 Max. Display Volume: 2.7 cm3
 Max. Display Mass: 7lbs.
 Total Components required: 17
 Total PCB Area: 103.32
 Input Voltage Requirements: 5 to 6VDC
 Input Current Requirements: 200mA.
 Max. Total DC Power: 7.5Watts
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Standard Requirement for Display
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Min. Operational Ambient Temperature Range: 0
to 32 degree Celsius.
Min. Operational/Storage Ambient Humidity
Range: 100 %Rh.
Min. Storage Ambient Temperature Range: -50 to
65 degree Celsius.
Applicable Safety Standards: UL 873.
Applicable EMC Standards: IEC 61000-4-11.
Estimated Max. Production Lifetime: 5 years.
Reliability in MTBF: 0.04 years.
Service Strategy: Repair.
Standard Requirement for Display
Full Warranty Period: 2 years.
 Consumption Power: 7.5 Watts.

Safety Requirements for Dispaly
 Compliance
 Compliance
 Compliance
 Compliance
 Compliance
 Compliance
 Compliance
 Compliance
with IEC61000-4-2
with IEC61000-4-3
with IEC61000-4-6
with IEC61000-4-8
with MIL-PRF-38535
with MIL-STD-202
with UL 1741
CISPR11- RF Emissions
Display: Block interface
Power Signals
Type
Direct
ion
Voltage
Nominal
Power supply
Analog Signals
DC
Power
Input
Type
6V
Direct
ion
Voltage Range
Min
5V
Coupling
Freq
Nomin
al
Max
7.5V
Freq Range
Min
DC
Voltage
Max
Amplitu
de
N/A
Max
N/A
Impedance
Min
Max
% VReg
VRipple
Curr
ent
Max
Max
Max
0.01
1.8V
Freq Range
Min
Max
1.0A
Leaka
ge
Max
Signal Conditioner
Analog
Input
Direct
5.0V
800
ohm
1.2Koh
m
DC
N/A
10pA
Signal Conditioner
Analog
Input
Direct
5.0V
800oh
ms
1.2Koh
ms
DC
N/A
10pA
Input analog signal
from signal
conditioning block
BlockInputBreakdown
of 5 to 6 VDC
Multiplexer
(CMOS Analog Switch)
Hysteresis Buffer
from power supply
A/D Converter
Analog Debounce
7 segment LEDs
Mechanical Switch
User
Block Detail Design
Block Detail Design
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Multiplexer which is the CMOS Analog Switch
MAX319 takes the analog input signal from the
signal conditioning block and the output of the
Switch is connected to A/D converter.
Analog Switch is implemented in order to ensure
that the switch bounce stops before the
Hysteresis gate reaches its input threshold
voltage.
CMOS Hysteresis gate with a threshold voltage of
0.45 to 0.55V in order to pull the input out of the
threshold the first time the gate switches.
Mechanical Switch is used to select either the
temperature signal or weight signal as an input
for the Multiplexer.
Block Detail Design
ICL7107 A/D Converter is used to take the
analog input signal from the Multiplexer
and convert it to digital signal which
provides an input digital signal to the 7segment LEDs.
 7-segment LEDs is used to display the
temperature and weight measurements in
numbers.
 3 rightmost LEDs display numbers from 0
to 9 and the leftmost LED can only display
number 1 and if the measurement is
negative, it displays a “-” sign.

Block Detail Design

Specifications:

Supply Voltage: +/-5V (Symmetrical)
Power requirements: 200mA (maximum)
Measuring range: +/- 0 – 1.999 VDC in four ranges.
Accuracy: 1%
•
Features:
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Small size.
Low cost.
Simple adjustment.
Easy to read.
Durable.
Reliability Assessment, Growth
(Display Block)
Total
FITS: 27.761
MTBF: 0.036021
Dominant part for unreliability with highest
lamda: switch
Implementing a flip-flop instead of a
mechanical and manual switch
Load Cell Block
Owner: Nick Bouche
The load cell will measure the weight of the keg and its contents. This will
then be calibrated such that the weight of the keg will be zero so that only
the contents are weighed. This weight will then be converted to volume.
Standard Requirements
 Compliance
with IEC 60332-2-34
 Compliance with IEC 61000-4-5
Performance Requirements
 Accurate
within 0.8 lbs
Block to Block Interface for Load Cell
Breakdown Diagram
Power
Force Sensor
Zero Calibration
Weight to Volume Converter
To Signal Conditioner
Detail Design

Force sensor will
be used for
measuring weight
Solenoid Valve Block
Owner: Nick Bouche
The solenoid valve block will dispense liquid per the users’ input. The user
must enter in the correct code and then select one of a number of sizes.
This block will be responsible to dispense liquid for only as long as needed to
pour the correct amount of liquid.
Standard Requirements
 Compliance
with CSA C22.2
 Compliance with IEC 61000-4-5
Performance Requirements
 Dispense
the amount of liquid
wanted using
– A known flow rate
– A timer
 User
will select a position on a switch
to determine the amount of time the
valve will open
 User will push a button to open the
valve for the select time period
Block to Block Interface for Solenoid Valve
Breakdown Diagram
Size 1
Password from keyboard
Power
Size 2 Size 3
Flow Control
Relay
Solenoid Valve
Detailed Design
Detailed Desgin
R1 will vary based on the users’ selection
of volume of liquid to be dispense.
 R1 determines how long the signal will be
5V before dropping to 0V.
 R3 acts to create a voltage divider so that
the voltage at that point is 5V so that it
matches the input signal from the keypad.
 The switch that closes the circuit at t=0
will be a momentary N.C. push button.
 The output from this circuit will be the
input for the relay which will then feed
power to the valve.

Reliability Assessment, Growth
(Solenoid Block)
 Total
FIT’S : 319.3
 MTBF : 0.0031319
 Dominant part for unreliability are
the relay and the solenoid valve.
 A relay and a solenoid valve that
would have higher maximum rated
voltage would improve the reliability.