Transcript Presentation

ECE ILLINOIS
Smart Thermometer
Group 20
Alisher Kurmanbay
Praful Mehrota
TA: Jacob Bryan
ECE 445 Spirng 2016
Motivation
• Current bath thermometers simply give you the temperature
of bath but don’t actually help create a bath of a given
temperature.
• Help parents prepare bath for their kids.
• Help the elderly with their bathing needs, especially
those who are unwell.
http://photo.elsoar.com/cute-babies-funny-kids-at-bath-time.html
Features
• Predict bath temperature after it has been filled.
• Change current prediction as tap temperature changes.
• Predict temperature of bath, after it has been filled, for next
x minutes where x<60 minutes.
• A user friendly mobile app for helping user
Design
Circuit
PCB
Final Demo Perfboard
System Overview
Hardware:
Sensor Unit
Bluetooth Module
LCD
Power Unit
Microcontroller
Software:
Atmega Code
Android App
for User
Interaction
Sensor Unit
•
•
•
•
DS18b20 One Wire Sensor
Used to determine temperature of air and tap water.
We used analog thermometer to show accuracy of our final
prediction by comparing it against actual bath temperature.
+/- 0.5 C accuracy for -10 to +85 C.
Electrical Rating:
3 - 5.5V supply, 1.5mA active
current, 7.5mW
https://www.sparkfun.com/products/11050
Sensor Unit
•
•
•
•
•
HC-SR04 Sensor
Used to determine the changing height of the water bath.
As a non-contact sensor, helps to get over the hassle of
waterproofing.
Surprisingly, is waterproof on
its own.
+/- 0.5 cm accuracy.
Electrical Rating:
5 V working voltage, 15mA working
current.
https://www.sparkfun.com/products/11050
Sensor Unit
• Determine the flow rate of the tap. This is in turn used
during our calculations when we compute heat loss, by
integration.
• Error of around 10%.
• Range: 0 - 0.5 L/s
• In general, water flow is around
0.04L/s.
• Electrical Rating: 5-18 V, 15mA
https://www.sparkfun.com/products/11050
Bluetooth module
HC-06 Bluetooth Transceiver
• Used to communicate with our android app, over Bluetooth.
• Is effective over a range of 30 feet.
• Electrical rating: 3.3-6 V, 20-40mA
https://www.sparkfun.com/products/11050
LCD
• Used to display the value of the predicted and actual
temperature.
• The value of the current temperature keeps updating, so it's
imperative for the LCD to show the change with substantive
delay. The Liquid Crystal Library helps us with this.
• Electrical Rating: 5 V DC
https://www.sparkfun.com/products/11050
Power Unit
• Responsible for powering up the entire circuit.
• Use a 9V alkaline battery to power the circuit in conjunction
with a linear voltage regulator - 7805 Regulator with
0.33uF and 0.1uF capacitors.
• The 7805 Regulator supplies 5V +/-0.25 V DC power to
circuit.
• The regulator requires the input voltage to be at least 7 V.
So, this in a way protects the circuit from voltages below
7V.
https://www.sparkfun.com/products/11050
Schematic
Microcontroller
Atmega 328P
• Microcontroller with enough internal memory and calculating
power.
• We needed at least 9 digital and 6 analog pins to control all our
devices.
• Electrical Rating: 5 V DC
https://www.sparkfun.com/products/11050
Calculations: Law of cooling
𝒕=𝒙
𝑸𝒄𝒖𝒓𝒓𝒆𝒏𝒕 = 𝑸𝟎 +
𝑸𝒍𝒐𝒔𝒕
𝒕=𝟎
Where
𝑸𝒍𝒐𝒔𝒕 = 𝒉𝑨(𝑻𝒂𝒊𝒓 − 𝑻𝒘𝒂𝒕𝒆𝒓 (𝒕))
And temperature projection is governed by
𝑻𝒘𝒂𝒕𝒆𝒓 𝒕 = 𝑻𝒂𝒊𝒓 + (𝑻𝒘𝒂𝒕𝒆𝒓 𝒊𝒏𝒊𝒕𝒊𝒂𝒍 − 𝑻𝒂𝒊𝒓 )𝒆−𝒌𝒕 =
𝑸𝒄𝒖𝒓𝒓𝒆𝒏𝒕
𝒎𝒄
Simulation Graph
Bath temperature vs time
(Room temperature 25Cº)
33.00
Temperature in Cº
32.00
31.00
30.00
29.00
28.00
27.00
26.00
25.00
1
2
3
4
5
6
7
8
9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31
Time in minutes
Prediction
Actual Result
Simulation Graph
Bath temperature vs time
(Room temperature 25Cº)
Temperature in Cº
40.50
40.00
39.50
39.00
38.50
38.00
37.50
37.00
36.50
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
Time in minutes
Prediction
Actual results
21
22
23
24
25
26
27
28
29
30
31
32
Simulation Graph
Bath temperature vs time
(Room temperature 23.43Cº )
40.50
Temperature in Cº
40.00
39.50
39.00
38.50
38.00
37.50
37.00
36.50
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
Time in minutes
Prediction
Actual Result
21
22
23
24
25
26
27
28
29
30
31
32
Simulation Graph
Temperature of Bath vs Time
70.00
Temperature in Celsius
60.00
50.00
40.00
30.00
20.00
10.00
0.00
0.00
20.00
40.00
60.00
80.00
100.00
120.00
140.00
160.00
Time in minutes
At 32C
At 37C
At 40C
At 45C
At 65C
At 18C
At 21C
At 22C
Air temperature 25C
Calculations
Heat Transfer equation
𝒕=𝒙
𝑸𝒃𝒂𝒕𝒉 =
𝒕=𝒙
𝑸𝒈𝒂𝒊𝒏𝒆𝒅 +
𝒕=𝟎
𝑸𝒍𝒐𝒔𝒕
𝒕=𝟎
𝒉(𝒕𝒙+𝟏 )
𝑸𝒈𝒂𝒊𝒏𝒆𝒅 = 𝒄 ∗ 𝑻𝒕𝒂𝒑𝒘𝒂𝒕𝒆𝒓 (𝒕𝒙 ) ∗
𝑨 ∗ 𝒓𝒅𝒉
𝒉(𝒕𝒙 )
Simulation Graph
Temperature in Cº
Heat transfer simulations
39
38
37
36
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33
32
31
30
29
28
27
26
25
24
23
22
21
20
0
1
2
3
4
5
6
7
8
9
Cases #
Prediction
Actual Result
10
11
12
13
14
15
Mobile App
•Basic mobile app to interact
with the user.
•Involved establishing a basic
request response system with
the Bluetooth system, to
receive data.
•The app displayed prediction
data for the next x minutes,
where x<60.
Challenges
• One of the biggest challenges of our project is determining a
specific value for heat transfer coefficient to reduce the error
bound. This value changes depend on environmental factors such as velocity of air, humidity, temperature of air and
temperature of bath.
• Ultrasonic Sensor: The sensor sometimes returned outlandish
values because of changing height.
Future work
• Create more user interaction via app.
• Add stop ability by touch/movement.
• Ambitious Extension:
• The Smart Bath Project: A complete project where user
can prepare his own bath without putting any physical work.
Successes
• Predictions were accurate in the range of ±1Cº
• All our modules functioned well and acted in harmony
• Mobile app was interacting with our system and delivered
important analysis information to user.
• Our simulation video can be seen from:
https://www.youtube.com/watch?v=-Wlc5rELwcg
Why no PCB in Final Presentation?
• Had issues with PCB due to interaction between bluetooth and
LCD, resulting in garbage values showing up on LCD.
• Involved significant rewiring of the PCB. We didn't want to create
more problem by drawing out traces.
References
Newton's Law of Cooling", Ugrad.math.ubc.ca, 2016. [Online]. Available:
http://www.ugrad.math.ubc.ca/coursedoc/math100/notes/diffeqs/cool.html .
[Accessed: 08 Mar 2016].
"Temperature Sensor Waterproof (DS18B20) SEN11050 SparkFun
Electronics", Sparkfun.com , 2016. [Online]. Available: h
ttps://www.sparkfun.com/products/11050 . [Accessed: 08 Mar 2016].
Heat Loss from Open Water Tanks", Engineeringtoolbox.com . [Online].
Available: http://www.engineeringtoolbox.com/heatlossopenwatertanksd_286.html . [Accessed: 08 Mar 2016].
QUESTIONS?