Life’s Ultimate Problem… Solved By…

Preliminary Design Review Team Iron Chefs Ahmad Alawadhi Eric Willuweit Kegan Grimes Kyle Chessman Sean Flodberg

Overview  Project Objective  Background  Approach  Sub-system Implementation  Member Roles  Schedule  Contingency Plan Chessman

Project Objective  The goal of our project is to innovate the existing induction cooktop design with designated cooking locations and creating a “zone free” cooking range. Chessman

Existing Cooktops  Cook tops use one large copper coil for each designated zone.  The copper coils create a magnetic field which induces eddy currents into the cookware above it.  These small currents heat the cookware through resistance of the material. Chessman

Background  Cookware used must be a ferromagnetic material as the heat produced arises from Eddy Currents and the resistance caused by the skin layer of the metal.  Cookware must be flat- bottomed to maintain efficiency. Universal Symbol for induction cooking Chessman

Approach  Utilize smaller copper coils in place of the large single coils.  Sense cookware’s location on the “zone-free” range.  Supply power to the coils that sense the cookware. Chessman

Inputs and Outputs Alawadhi

System Flow Diagram Alawadhi

Sub-system Implementation  Systems  Indicator LEDs  Copper coils  Sensors Alawadhi

Indicator LED Sub-system  LEDs indicate which coils are being supplied with power.  LEDs on temperature knobs lit with same color LED as the powered coils to display which coils the knobs correspond to. Willuweit

Copper Coils Sub-system  Power supplied through the IGBTs  PWM signal generated from the MCU  Current transformer to feedback circuit  To optimize power transfer Willuweit

Coil Construction  3 inch flat copper coils  “Litz” copper wire  Small gauge insulated copper wire wound like a rope into a larger gauge wire for transporting high frequency currents  Take advantage of the “skin effect” used by transmission lines Willuweit

Sensor Sub-system  Sensors change resistance when cookware is placed above them, causing a change in voltage.  High gain amplifier boosts the small signal to be noticed by the microcontroller. Willuweit

Testing Potential Sensors  Photodiodes  Induction sensing  Infrared LEDs  Pressure sensing / Mapping Willuweit

MCU - Microcontroller  Output at least seven PWM signals for our desired hexagon shaped design.  Read analog signals from the feedback circuit and adjust PWM output accordingly  Controls LEDs  MCU Requirements  PWM outputs for each coil  A/D converters for each coil feedback  Possible Choices:  ARM A series  ATXmega64 Willuweit

Amplifier Circuits  Driver Amplifier  A class D Amplifier  Completely digital  Input from the PWM supplied from the MCU  Energy efficient  High Gain Amplifier  Op-amp with feedback circuit  Could also use a transistor combination circuit MCU PWM Signal Coils IGBT Grimes

The Cookware, the Coil and the Capacitors (LC Tank)  The coils act as an inductor  When placed in series with capacitors, the two form an LC circuit also known as an “LC Tank” Grimes

Feedback Circuit  Step-down transformer to supply 5V back to the MCU  Measures analog voltage signal from LC tank  MCU adjusts frequency of the PWM signal supplied to the IGBTs  Frequency will begin high (60kHz) and decrease down to potentially 19kHz  When the voltage amplitude peaks and is measured by the MCU, the frequency is maintained and the optimum power transfer has been reached Grimes

Power  Supplied with 120/240 AC voltage from the wall outlet  Rectified to a DC voltage of 5V and 15V for the MCU and analog components  Transform the 15V to 325V DC to be supplied to the IGBTs  PWM signal controls the “on/off” state of the transistors creating an effective square wave AC signal. Grimes

Power Transfer  The alternating square wave from the IGBTs creates an alternating magnetic field in the copper coils  The field is directed into the cookware, inducing eddy currents  Each individual coil will create a portion of the overall field necessary to heat the cookware  The number of coils needed varies with the cookware size Grimes

Power Requirements  With a 22 cm diameter iron pot on top of range, the system will deliver approximately 2500 watts  At an input of 60Hz  Frequency supplied to the coils is 25kHz  At a 100 peak-to-peak current to the coils  This would be divided between seven coils accordingly Flodberg

Feasibility  Materials  Availability/ Creation of copper coil windings  What kind of surface?  Existing surfaces are Ceran  Combination of glass and ceramic  Sensors sensitivity to temperature  Power  Ability of small coils to generate energy equivalent to the large coils Flodberg

Member Roles TasksAhmad Alawadhi Eric Willuweit Kegan Grimes Kyle Chessman Sean Flodberg Software Design MCU Feedback Debugging Hardware Design Sensors Drivers/ Amplifiers Power Supply Copper coils Debugging Flodberg

Timeline Flodberg

QUESTIONS