A Touchless Faucet with Temperature Control based on Human ...

Touchless Faucet with Temperature Control

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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


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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.

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