The document describes how a microprocessor controls the operation of a microwave oven. It explains that the microprocessor receives input from devices like the keypad and door switch and uses those inputs to make decisions on operating output devices such as the microwave generator, display, and fan. The microprocessor converts AC power to DC power required to run the system and precisely coordinates timing and devices during the cooking process based on the programmed settings.

1. Made by:
Akash lal

2. The Microprocessor
• Many gadgets, devices, appliances and machines
have microprocessors controlling their operation.

3. For a microprocessor to
control device, it has to:
• For a microprocessor to
control device, it has to:
• Make decisions based on
the detected changes.
• Activate appropriate
output devices according
to decisions made.
Input Devices
Input
Process
Microprocessor
Controller System
Process
Output Devices
Output

4. Component
• Here are some of the devices are used in a
microwave oven:
1. A microwave generator produces the
microwaves that cook the food.
2. A lamp illuminates during the cooking
process.
3. A motor drives a turntable so that the food
rotates and cooks evenly.
4. A display indicates the cooking time and
the selected cooking mode.
5. A sounder beeps when the cooking period
is complete.
6. The keypad enables the cooking time to be
set, cooking mode to be entered and
START/STOP cooking selected.
7. A door switch detects when the door is
open.
8. A fan removes steam that is generated by
cooking.

5. • To control the operation of the microwave oven, there is a
printed circuit board (PCB) containing the microprocessor
system.

6. Power Supply in Oven
• To power the microprocessor and the various devices, the
microwave oven is connected to the power source.
• The power source is a high voltage, alternating current (AC) supply.
• The circuitry of the microprocessor and some of the devices require
a lower, direct current (DC) voltage.
• A power supply unit converts the AC supply to the required DC
voltage level.

7. Input Devices
• The INPUT devices to the microprocessor system are:
1. The keypad
2. The door switch

8. Door Switch
• The door switch requires one input line
to the microprocessor system.
• The input line is a wire that carries an
electrical signal from the door switch to
the microprocessor system.
• The switch could be in one of two
positions.
• With the door open the switch would
be open, and with the door closed the
switch would be closed.
• The microprocessor can determine the
position of the switch by the electrical
signal on the input line.

9. Keypad
• The keypad has many
buttons and requires several
lines connecting it to the
microprocessor system.
• For each button pressed on
the keypad, a unique digital
code is sent to the
microprocessor.
• In this way the
microprocessor is able to
detect which button has
been pressed.

10. Output Devices
• The output devices from the microprocessor system
are:
1. Microwave generator
2. Turntable motor
3. Display
4. Lamp
5. Sounder
6. Fan

11. • Here are the input and output connections to
and from the microprocessor.

12. • If the microprocessor and devices are taken out of the
cabinet, we can view the connections more easily.
Timer

13. System Operation
• The cooking mode is
selected on the keypad and
the cooking period set.
• The microprocessor reads
the settings input on the
keypad into its memory.
• Signals are sent to the
display to indicate the
cooking mode and cooking
period set.

14. • When the START button is pressed and the
door is shut, the microprocessor carries out
the following:
1. Starts the electronic timer with the cooking
period
2. Switches the fan on
3. Switches the lamp on
4. Starts the turntable motor running
5. Switches the microwave generator on
The microprocessor is able to carry out these
tasks very quickly so they appear to happen at
the same time.

15. • If the door is opened, the microprocessor will detect it and stop the
cooking process by switching off the fan, microwave generator and
turntable motor.
It may also put a message on the display, DOOR OPEN.