a touchless faucet with temperature control based on human
TRANSCRIPT
Touchless Faucet with Temperature Control
1
A Touchless Faucet with Temperature
Control based on Human Thermal
Comfort
Project Proposal
Group #22
Mo Xie, Yu Min, Xuanyu Chen
TA: James Norton
ECE445
Sept 15, 2015
Touchless Faucet with Temperature Control
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Table of Contents
1.0 INTRODUCTION
1.1 Statement of purpose......................................................................................3 1.2 Objectives........................................................................................................3
1.2.1 Goals........................................................................................................3 1.2.2 Functions.................................................................................................3
1.2.3 Benefits....................................................................................................3 1.2.4 Features...................................................................................................4
2.0 DESIGN
2.1 Block Diagram....................................................................................................4 2.2 Block Descriptions.............................................................................................4
2.2.1 Infrared Sensors.......................................................................................4 2.2.2 Temperature Sensors...............................................................................5
2.2.3 A/D Convertor..........................................................................................5 2.2.4 Micro-controller.......................................................................................5
2.2.5 Power........................................................................................................5
2.2.6 Valves.......................................................................................................5
2.2.7 Faucet.......................................................................................................5
2.3 Circuit Schematics.............................................................................................6
2.4 Software Flowchart...........................................................................................7
3.0 REQUIREMENTS AND VERIFICATION
3.1 Table of Requirements and Verification............................................................8
3.2 Tolerance Analysis.............................................................................................9
3.3 Calculation.........................................................................................................9
4.0 COST AND SCHEDULE
4.1 Cost Analysis..................................................................................................10
4.1.1 Labor........................................................................................................10
4.1.2 Parts.........................................................................................................10 4.1.3 Grand Total..............................................................................................10
4.2 Schedule.....................................................................................................11
5.0 SAFETY
5.1 Safety in lab...............................................................................................12 5.2 Safety in testing system.............................................................................12
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1.0 Introduction
1.1 Statement of Purpose
Research shows that human's thermal comfort is mostly dependent on thermal
exchange between the environment and the body. e.g., hot if the body dissipates
heat faster than gaining(International Standard Organization 7730, 2006). The effect
is reflected on our skin temperature as the skin is the medium of the exchange, with
a neutrally comfortable zone of 27-34 degrees(Human Thermal Comfort, 1995). In
the reality, touchless faucets we generally use always generate water flow with fixed
temperature which sometimes could be too hot or cold for hand washing. Especially
in the winter, when our skin is cold and the water is hot. Our project aims to develop
a touchless faucet by designing a circuit that detects user's skin temperature, and
controls the combination of hot and cold water to a desired output that achieves
thermal comfort.
1.2 Objectives
1.2.1 Goals
Output water when user detected.
Temperature of water should be automatically adjusted.
Build a testing system.
1.2.2 Functions
Sensing user's skin temperature.
Calculate temperature of "comfortable" water.
Control the water output temperature.
Gradually increase the output temperature to the comfortable zone when skin is cold.
1.2.3 Benefits
Reduce human efforts.
Reduce chance of pain.
Always output comfortable temperature
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1.2.4 Features
Touchless feature makes it easy to use.
Comfortable water temperature.
2.0 Design
This section describes the whole system of our work and how it works.
2.1 Block Diagram
A complete gathering of block in the system and how blocks transfer signal between each
other.
2.2 Block Descriptions
A detailed text description of how each of the blocks in the block diagram functions.
2.2.1 Infrared Sensor
The infrared sensor senses the human hand's existence and the skin temperature, which
outputs a voltage to the micro-controller as a turn on signal. The analog voltage output will
be sent to the input of A/D convertor.
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2.2.2 Temperature Sensors
The two temperature sensors that in two tanks which storing hot and cold water will
measure the temperature of water. The outputs will send to A/D as voltage signals.
2.2.3 A/D Convertor
The A/D Convertor receives analog voltage signals from both temperature sensors, it
then converts the voltage signals into digital signals to output to the micro-controller.
2.2.4 Micro-controller
We are going to build a micro-controller on a breadboard which works just like Arduino.
The micro-controller will process inputs from A/D and generate output to valve switch. The
micro-controller will also calculate the warm water temperature according to human hands’
temperature (T’ °C), hot water’s temperature (H °C) and cold water’s temperature (C °C).
Then micro-controller will control the open or close of switches of valves according to the
ratio between mass of hot water and cold water.
2.2.5 Power
Battery is used to power the Micro-controller on a breadboard, and valve switches.
Operating at 5V +/- 0.25V and 1A +/- 0.25A.
2.2.6 Valves
The switches of the two valves receives control signal from the micro-controller. Control
signals will control the valves to be closed, or opened to a certain precision.
2.2.7 Faucet
Like all touchless faucets do, it only generates water flow when hands are detected, but
the hand skin's temperature is also read into the controller at the same time, by processing
the data through the micro-controller, the faucet will output a desirable temperature of
water.
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2.3 Circuit Schematics
1. Vcc will connect with power expect valve and GND will connect with ground.
Below is the schematic of our sensors. We have digital control in this sensor, so we do not need A/D converter to transfer analog signals into digital signals.
Pin DRDY of sensors will connect with the pin ‘port D’ of ATmega328.
2. Schematic of self built micro-controller referring to Arduino architecture.
The pin ‘A0 to A5’ will connect with the Vcc of the valve. This will control the open or close of the valve.
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3. Below is the schematic of valve switches.
The Vcc and GND of SEN 1 PIR will always connect to ground. This will make SEN 1 PIR don’t work. And the output of micro-controller will connect with the rest Vcc
to control the valve.
4. Power
Since sensors and the microprocessor are powered by 5V DC supply, and normal
batteries do not offer 5V, we need a voltage regulator circuit to fix the Vcc to 5V.
2.4 Calculation
Equation for mixing difference temperatures of water:
T = expect temp. of output, a = hot water temp. b = cold water temp
= ratio of hot and cold water
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2.5 Software Flowchart
Below is a description and software flowchart of the programmed micro controller.
The software takes three digital inputs from A/D controller each reflects temperature of the
infrared sensor and two temperature sensors. While a hand is not present, the program
iterates in a loop. When a hand comes to present, the program then process the inputs to
indicate if the water temp needs to be gradually increased when the hand is cold, or directly
calculate the output temp. By having the output temp, the program then calculates a
reasonable and accurate combination of cold and hot water, and send outputs to control the
valves. The water will continue to flow while hand is still present. Otherwise the done signal
will be triggered, and the program goes into the outer loop and waits.
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3.0 Requirements and Verification
3.1 Table of Requirements and Verification
Requirements Verification Points
Micro-Controller:
High signal generated by the
micro-controller to control the
switches should be above 5V
Use a multimeter in parallel to the
valve switches. When the valve is
open, the corresponding switch must
have a high signal.
__ / 25
Temperature Sensors:
Must reflect temperature
through directly related voltage
by +/- 0.5 degrees offset.
Take readings using a multimeter on
the sensor's voltage for every 2
degrees for temperature ranging from
0-50 degrees. Plot a diagram and
apply linear fit.
__ / 25
Infrared Sensors:
1. Must detect when a hand is
present
2. Must reflect temperature
through directly related voltage
by +/- 0.5 degrees offset.
1. When a hand is present, voltage of
the signal is measured using
multimeter and should be above 1V
2. Take readings using a multimeter
on the sensor's voltage for every 2
degrees for temperature ranging from
10-36 degrees. Plot a diagram and
apply linear fit.
__ / 25
Valves:
Must control output water flow
to make sure the water is in
correct temperature range by +/-
1 ºC
Use a thermometer to check
temperature accuracy and compare
the result with the calculation.
__ / 15
Power:
Must provide 5V +/- 0.25V and
1A +/- 0.25A
Use a multimeter parallel to the
battery for monitoring. Should be
generating 5V +/-0.25V and 1A +/-
0.25A
__ / 10
3.2 Tolerance Analysis
Because our main goal is to output a comforting temperature of water, that makes
correctly sensing the temperatures we need the most important part of this project. If the
sensors don't work accurately as we expected, for example, if the infrared sensor senses the
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user's skin temperature wrong, or the sensors attached to water tanks give us inaccurate
readings, there's even no chance to predict the output temperature resulting in possibilities
that the user feels too cold or hot. We will set up the test by measuring the sensors' voltage
using a multimeter, this voltage is then sent to the micro-control in digital signal and is
converted to a temperature in the control program. We will test every 2 degrees from 6 -50
degrees Celsius and plot a diagram to see if its linear. In average, the threshold of human
hands feeling cold/warm is within +/- 1 degrees Celsius difference by the skin
temperature(Method for quantitative estimation of thermal thresholds in patients, 1976,
figures 1,2). We want the accuracy of the sensors to be +/- 0.5 degrees for a better output.
Figure. 1 Figure. 2
4.0 Cost and Schedule
4.1 Cost Analysis
4.1.1 Labor
Name Hourly
Rate
Total Hours
Invested
Total = Hourly Rate *2.5 *Total Hours
Invested
Yu $30 125 $9375
Mo $30 125 $9375
Xuanyu $30 125 $9375
Total $28125
4.1.2 Parts
Parts Unit Costs Quantities Total
Micro-Controller $55 1 $55
Temperature Sensors DS18B20U $9 3 $27
Infrared Sensor TMP007 $18 1 $18
Touchless Water Faucet $75 1 $75
Valves $5 2 $10
Total $179
4.1.3 Grand Total
Labor $28125
Parts $179
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Total $28304
4.2 Schedule
Week Yu Min Mo Xie Xuanyu Chen
9/15 Prepare for
proposal
Prepare for
proposal
Prepare for
proposal
9/22 Draft circuits for
motors
Prepare for Mock
design review
Draft circuits for
controlling sensors
9/29 Prepare Design
review
Prepare to
purchase parts
Research for felt
air temperature
10/6 Run initial tests on
power source
Program the
controller
Initial tests for the
faucet
10/13 Assemble circuits Integrating the
whole circuit
Add power supply
to each element
10/20 Initial test for
motors
Initial test for
controller
Initial test for
sensors
10/27 Run precise tests
on motors
Prepare for Mock
presentation
Run precise tests
on sensors
11/3 Assemble the
entire system
Run tests on the
entire system
Debugging the
system
11/10 Ensure
functionality
Try to find
improvements
Further debugging
11/17 Fix errors Finalize the
project
Finalize the
project
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11/24 Prepare for final
demo
Prepare for final
demo
Prepare for final
presentation
12/1 Prepare for final
presentation
Prepare for final
Paper
Finalize
presentation
12/8 Finish final demos Finish final paper Lab checkout
5.0 Safety
5.1 Safety in lab
Even if this project does not require high voltage operation. Basic rules in the lab must
be obeyed.
1. At least two people in the lab at the same time.
2. Protect the batteries and other electronic components from short circuit.
3. Call 911 immediately after accident or cut the power and call 911 if applicable.
4. ABSOLUTELY NO WATER IN THE LAB
5.2 Safety in testing system
1. Hot water must be below or equal to 50 degrees Celsius, above which produces pain.
2. Keep electronic component insulated from water.