Smart Solar Water Heater

EP 315 Microprocessors Lab and EP317 Digital Lab ProjectAutumn 2014

Team Autobots

Anchal Gupta Roll Number 12D260003Pratik Agarwal Roll Number 120260029

Anamika Agrawal Roll Number 120260017Department of Physics, IIT Bombay

November 6, 2014

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1 The Idea

Generally Solar Water heaters cannot be set to give exact temperature ofwater required, as they are heated by an uncontrollable source. This resultsus in standing in front of two taps and manually using PID to prepare abucket of water for us. Mostly we miss it and we end up using water andheat energy inefficiently. We present a system to do this mixing for you andsaving energy and water for rest of the world.

2 Features of ‘Helioptimus’ Prototype

Our prototype - Helioptimus (named after helios- the sun and OptimusPrime, the great fictional character of Transformers fame) is at this stagea water mixer which mixes hot water with cold water to give water at theuser-defined desired temperature. A schematic diagram is presented below :

Figure 1: Schematic Diagram of Helioptimus

In our prototype, we have used following modules:-

1. Temperature Sensors

2. Volume Sensor

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3. Microcontroller

4. Pumping System

5. Digital Seven Segment Display

A brief description of each module is as follows.

3 Temperature Sensors

We have used Pt100 Platinum Resistance Thermometers(PRTs) for measur-ing temperature of water. The principle of operation is that the resistanceof the platinum element within the thermometer varies nearly linearly withtemperature. The temperature coefficient for our working range of operationwas taken to be 0.385Ω/oC. The exact conversion factors are given in thetable attached at the end. Circuit diagram is presented below :

Figure 2: Circuit diagram for Temperature sensor circuit

4 Volume Sensor

We have used ultrasonic ranging module HC - SR04 (see fig.3) to measurewater level in the bucket. It includes ultrasonic transmitters, receiver andcontrol circuit. The basic principle involved in its functioning were:

1. Using a short pulse trigger.

2. It then automatically sends eight pulses of40 kHz and detect whetherthere is a pulse signal back.

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3. The time duration is the time from sending the ultrasonic to its return.

4. We have calibrated the different time durations in microseconds withthe amount of water filled in the bucket

5. Hence, in our code volume is measured in microsecond units.

Figure 3: Volume (level) sensor- HC-SR04

5 Microcontroller

We have used Arduino board with ATMega168 (see fig 4) mounted on itto do the PID calculations. The microcontroller receives the temperatureinformation of hot water and cold water continuously and decides which oneit needs to pour into the mixer tank to get the desirable temperatureusingefficient PID code. The mixing is stopped when required amount of waterhas reached according to the volume sensor.

Figure 4: Arduino ATMega168 microcontroller

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6 Pumping System

We have used JQC-3FC/T73 model 12V DC PCB mounted sugarcube relayfor controlling the pumps used. The circuit simply includes an amplifier tooperate a relay to switch on or off the pumps. The circuit diagram is givenin fig.5.

Figure 5: Circuit Diagram for Pump Relay System

7 Digital SSD

A digital seven segment display is used to display the temperature inputwhich the user gives.

8 Problems faced during the course of the

project

1. The pumping rate is a function of the water level in the bucket andhence was not a constant, contrary to our assumption. This problemwill be minimized on a large-scale application.

2. Temperature sensors of better resolution could’ve been used.

3. Ultrasonic level sensors gave wrong readings due to ripples in water,interference from wave fronts (reverberation) and other noise factors.

4. Heat dissipation by the sensor may cause artificially high temperature.

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9 Possible improvisations

1. A solenoid valve system can be used to control water flow instead ofthe pumping system that we have used.

2. Better volume measurement systems like pressure sensors can be used.

3. Waterproof temperature sensor probes of better resolution can be used.

4. Outlet control from mixer tank can be included.

5. Timer can be included.

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10 Codes used in the microcontroller

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Reference: RTD Temperature vs. Resistance

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