microwave oven using 8051 microcontroller. Basic knowledge how microcontroller used in microwave oven.And at last some harmfull effect of microwave oven for cooking food.

1. MICROWAVE OVEN
Using
microcontroller
By-
Manish Bhagat

2. CONTENTS
• Introduction
• Principle
• Discovery
• Working
• Components of microwave oven
• The DS1620 Digital Thermostat
• Algorithm of the devices operation.
• Health Effects

3. Microwaves radiation are a form
of electromagnetic
radiation with wavelengths ranging
from one meter to one millimeter;
with frequencies between 300 MHz
and 300 GHz .It is lie between radio
and infrared frequency.

4. • Magnetron is a tube in which electrons
are affected by magnetic and electric
fields in such a way to produce micro
wavelength radiation.

5. INTRODUCTION
• A microwave oven, is a
kitchen appliance that can
come in many different
sizes and styles employing
microwave radiation
primarily to cook or heat
food. This is accomplished
by using microwaves,
almost always emitted from
a magnetron, to excite
water (primarily) and other
polarized molecules within
the food to be heated. This
excitation is fairly uniform,
leading to food being
heated everywhere all at
once

6.  Microwave oven works by passing non-ionizing
microwave radiation, usually at a frequency of 2.45 GHz
(a wavelength of 12.24 cm), through the food.. Water, fat,
and other substances in the food absorb energy from the
microwaves in a process called dielectric heating. Many
molecules (such as those of water) are electric dipoles,
meaning that they have a positive charge at one end and
a negative charge at the other, and therefore rotate as
they try to align themselves with the alternating electric
field of the microwaves. This molecular movement
creates heat as the rotating molecules hit other
molecules and put them into motion. Microwave heating
is most efficient on liquid water, and much less so on fats
and sugars (which have less molecular dipole moment),
and frozen water (where the molecules are not free to
rotate).
PRINCIPLE

7. Discovery
Cooking food with microwaves was discovered by
PERCY SPENCER while building magnetrons for
radar sets. He was working on an active radar set
when he noticed that a peanut chocolate bar he
had in his pocket started to melt. The radar had
melted his chocolate bar with microwave. Then he
cooked popcorns and food in microwave . Spencer
created a high density electromagnetic field by
feeding microwave power into a metal box which it
had no way to escape. When food was placed in
the box with the microwave energy, the
temperature of the food rose rapidly.

8.  Every microwave oven contains a magnetron, a
tube in which electrons are affected by magnetic
and electric fields in such a way to produce micro
wavelength radiation. This microwave radiation
interacts with the molecules in the food. All wave
energy changes polarity from positive to negative
with each cycle of the wave and this cause the
polar molecules to rotate at the same frequency
millions of times a second. All this agitation
creates a molecular friction within the food and
at last this heats up the food.
WORKING

9. Components of microwave oven
Magnetron capable of emitting microwaves of
a frequency of 2,450 GHz and a power of
700/800W
 HV transformer (for converting voltage
from 220/110V to 4kV)
Temperature sensor for controlling the
actual heat generated by the magnetron
Keyboard (4x4 matrix keyboard)
LED/LCD display
8051 Microcontroller

10. Interfacing of a Keyboard
The sole purpose of keyboard application is the need
to incorporate the user input.
4 keys are used for inputting the time
(10min,1min,10sec,1sec, pressing each of these adds an
appropriate amount of memory to the timer counter),
2 for inputting the weight of the material to heat
(1kg,100g),
1 for stop and 1 for start, and the remaining 8 for the
preprogrammed options(6 associated just with time, 2
with weight).

11. Keyboard Interface

12. The DS1620 Digital
Thermostat
The DS1620 Digital Thermostat provides 9-bit
temperature readings. It has three alarm outputs, so
the device can also act as a thermostat. The
DS1620, which incorporates a 3-wire interface can
be controlled using an 8051 Microcontroller

13. Temperature Control of the DS1620
The thermostat outputs of the DS1620 allow it to directly
control heating and cooling devices.
The output THIGH can be used to indicate that a high
temperature tolerance boundary has been met or
exceeded, or it can be used as part of a closed loop system
to activate a cooling system and deactivate it when the
system temperature returns to tolerance.
TLOW is driven high when the temperature of the device
falls below the limit set in the TL Register. TLOW remains
active until the DS1620's temperature becomes greater
than the value stored in the low temperature register, TL.

14. A Digital Thermostat
Interface

15. Interface

16. Algorithm of the devices operation.
After powerup and reset, the
oven waits for user input. The clock starts counting
up and displaying time on the LED display .
After each pressing of a key, updated data is sent
to the LED display to correspond with the
user input.
When the time and power settings are in the
program memory, the device waits for the 'start'
button to be pressed to execute the operation.

17. When Interrupt 1 goes low, we resume normal
operation.
When Interrupt 0 is raised (which implies, that
the temperature within the microwaves cavity
is too high), the magnetron output is set to 'Low‘
The keys are kept inactive while a program runs.
Only pressing stop once stops the execution

18. Harmful Effects
• microwave can strip away its original nutrients.
• Microwaves Destroy Breast Milk And Vitamin B-12
• Microwaves Create Carcinogens In Food when food is
wrapped by the plastic which is heated by the microwave
oven.
• Microwaves Can Change Your Heart Rate

19. Thank you