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 flatbottomed 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

IGBT
MCU
PWM
Signal
IGBT
Coils
High Gain Amplifier
 Op-amp with feedback
circuit

Could also use a
transistor combination
circuit
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
Tasks
Ahmad
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