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.

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 Features

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: V supply, 1.5mA active current, 7.5mW

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.

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: L/s In general, water flow is around 0.04L/s. Electrical Rating: 5-18 V, 15mA

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: V, 20-40mA

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

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 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.

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

Calculations: Law of cooling

Simulation Graph

Calculations

Simulation Graph

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

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, [Online]. Available: [Accessed: 08­ Mar­ 2016]. "Temperature Sensor ­ Waterproof (DS18B20) ­ SEN­11050 ­ SparkFun Electronics", Sparkfun.com, [Online]. Available: h ttps:// [Accessed: 08­ Mar­ 2016]. Heat Loss from Open Water Tanks", Engineeringtoolbox.com. [Online]. Available: d_286.html. [Accessed: 08­ Mar­ 2016].

QUESTIONS?