Easy Programmable Stove ECE445 Senior Design Spring 2013 Group Members: Benjamin Chng Ardy Winoto Cheng Han Lee Professor: Paul Scott Carney TA: Dennis Yuan

Outline Introduction Design Overview Requirements and Verification Challenges Future Work

Introduction A stove that automates the cooking process Allows user to choose from a database of recipes Stove carries out the steps

Objective Simple and safe interface for cooking Convenience

System Overview Hardware: Power supply Temperature/Proximity sensors Stove Arduino + Bluetooth Shield Software: Android application

System Overview

Sensors- Design Need proximity and temperature sensors Due to high temperature, contact sensors are out of the question Use IR-based sensors: Sharp GP2Y0A21K (proximity) Melexis MLX90614-ACA-000-TU (temperature)

Proximity Sensors- Design Two proximity sensors to detect presence of a cooking vessel

Proximity Sensors- Design Read analog output from sensors using Arduino Establish range of output values for cooking vessel detection When cooking vessel is not detected, no heat is delivered

Temperature Sensors- Design Two temperature sensors, one to monitor coil and one to monitor food

Temperature Sensors- Design Communicate with Arduino via two-wire SMBus protocol, with different slave addresses Convert received data into temperature values Find optimum sensing distance, orientation

Sensors- Requirements Proximity Sensors: Interface correctly with Arduino, detect cooking vessel with tolerance of ±2cm. Temperature Sensors: Interface correctly with Arduino, sense temperature of target with tolerance of ±10%

Sensors- Testing Proximity Sensors: Move cooking vessel 2 cm at 45° intervals, confirm detection Remove cooking vessel completely, confirm non- detection Temperature Sensors: Measure temperature of unloaded stove with sensors and a commercial IR gun, record results

Sensors- Results Proximity Sensors: Requirements met Temperature Sensors: Sensitive to orientation and thermal gradients Compensation needed for programming recipes Requirements met

Display Module- Design Android Application: “SmartStove” Receives input from controller Responds to button presses from input module

Display Module- Design Display recipe in ‘View Recipe’ screen Current recipe step prompt Current food/stove temperature

Display Module- Design Turning on Bluetooth(If it is not already on)

Display Module- Design Home Screen(with drop down menu clicked)

Display Module- Design View recipe pop-up

Display Module- Design Cooking screen

Display Module- Requirements Display all the above consistently All requirements met

Input Interface Android Application: "Smart Stove" Register button presses Use onClickListeners

Bluetooth Module- Design Seeed Bluetooth Shield Attached to the Arduino Universal Asynchronous Receiver/Transmitter (UART)

Bluetooth Module- Requirements Transmit and receive bytes of data accurately Testing performed with "Bluetooth SPP" app available on Play Store

Bluetooth Module- Testing Transmit o Send entire strings o Send character by character o Send character by character, with a delay Receive(sent from Android device) o Strings o Character by character

Bluetooth Module- Results Delay of 40ms required between each byte of data sent Android device will have to send character by character All requirements satisfied

Controller- Design Arduino State Machine

Controller- Design (Operate State) Check Reset/pot presence/safety temperature Retrieve instructions of current step Set PWM output Fixed heat level Maintain temperature Check advance condition Target temperature Timer User presses continue

Controller- Requirements Correct operation of state machine Process the recipe Advances to next step correctly Correct PWM output Turns off when Pot not detected Food temperature above 180 Celsius Stove temperature above 270 Celsius

Controller- Requirements Receive data from Android device Recipe Button presses Send data to Android device Update display based on step number Temperature readings Proximity sensor readings

Controller- Testing Simulate cooking process with “Bourbon Chicken” recipe Reset button Temperature and detect safety

Controller- Results Requirements met

Stove - Design Modification done to stove to regulate heat from controller Strategy: Pulse Width Modulation (PWM) scheme to regulate current Done using electromechanical relay PWM signal generated from Arduino

Stove - Design Exterior View of Stove

Stove - Design Interior view of stove

Stove - Design Single coil stove Wires from stove are connected to relay Current flow regulated by controller via relay

Stove - Design Electromechanical Relay Single pole double throw Rated 220V rms, 20A

Stove - Design The schematic of the BJT switch is shown below

Stove - Design Switch built using npn BJT Provides an output profile that mirrors PWM signal Output profile derived from 9 V power source Designed so that enough power is provided for relay’s operation

Stove - Requirements Modified stove should boil as fast as original stove Relay should switch successfully Relay should respond to PWM signal with little delay

Stove - Testing Measure the time taken for original stove and modified stove to boil Connect power across relay and measure switching and delay respectively

Stove - Results Requirements met

Power Management - Design To convert AC source from wall outlet to DC Method: Step down voltage from wall outlet to 25.2V rms Rectify and filter to 35.6V DC Stepped down again to voltage of individual components

Power Management - Design The schematic for the AC/DC converter is shown below

Power Management - Design Center-Tap Transformer Diodes rectify voltage profile Capacitor filters and “smooths” profile

Power Management - Design The simulation for the rectifier/filter is shown below

Power Management - Design The schematic for the Buck converter is shown below

Power Management - Design LM2576 Switch – fundamental to Buck Converter operation Made references to LM2576 datasheet in design

Power Management – Requirements Convert 120 Vac to 25.2 Vac “Smooths” output profile with small ripple voltage Convert 35.6 Vdc to 12 Vdc

Power Management – Testing Connect output signal into power probe and oscilloscope

Power Management - Results Requirements for transformer and filter met Requirement for Buck Converter not met Went with contingency plan (9V batteries) for demo

Overall Integration

Challenges Getting the power supply to work Finding optimum placement of sensors Obtaining correct parameters for PID controller Making Bluetooth transmission more reliable

Future Works Fix power supply module Larger recipe database Better UI for “SmartStove”

Credits Professor P. Scott Carney Mr Dennis Yuan Mr Ryan May Mr Kevin Colravy Mr Mark Smart Mr Skee Aldrich Mr Wally Smith