Page 162 - Electronic Mechanic - TP - Volume - 2

ELECTRONICS MECHANIC - CITS

MODULE 18: Domestic appliances

EXERCISE 160: Check controls on touch key pad of

microwave oven

Objectives

At the end of this exercise you shall be able to
• If your microwave keypad is not working you’ll need to test the membrane switch, and control board. Learn
how to troubleshoot with our microwave repair guide.

Requirements

Tools/ Materials
• Vom (multitester)
• Instructional/operational manual
• Screw driver
• Pliers
• Microwave oven - 1 No.

Procedure

Theory:A device called a magnetron inside the oven produces microwaves. The microwaves reflect off the metal
interior of the oven and cause the water molecules in food to vibrate. This vibration results in friction between
molecules, which produces heat that cooks the
Principle: High powered microwaves are generated and are allowed to fall on the food stuff. These waves heat
the molecules in the food particles evenly and cook the food.
Construction: In consists of a microwave generator called a magnetron, which is used to take electricity from the
power outlet and converts into high powered micro waves, as in figIn consists of a microwave generator called a
magnetron, which is used to take electricity from the power outlet and converts into high powered micro waves,
as in fig Fig 3.8.1 Microwave oven The food compartment is made up of reflective metal walls, just like a mirror,
to have effective focusing of microwaves onto the food particles. A rotating spinning arrangement, so called turn
table is used to rotate the food stuff so as to cook the food evenly. A channel of common wave guide is used to
transfer the microwaves from the magnetron to the food compartment. The total setup is completely surrounded
by strong metal boxes for safety. A timer display is also provided in the modern microwave ovens to choose
various options in cooking variety of food items like Gril
Touch key pad controls of Microwave oven
Working
Food to be cooked is placed on the turn table and the electricity is switched ON.

The magnetron converts the electrical energy into high powered radio waves, so called microwaves. The
magnetron blasts these microwaves into the food compartment through a channel called a common wave guide.
Microwave bounces back and forth between the reflective metal walls and reaches the food.
This Micro wave penetrates inside the food and makes the molecules in the food to vibrate. The vibrations will
cause heat then faster the molecules vibrate, the food becomes hotter. Thus in this way micro wave pass their
energy onto the molecules in the food and cook the food by heating it. The food is evenly cooked by rotating the
spinning or turn table slowly ,so that the micro waves are passed in each and every part of the food.

Advantages
It is portable,small in size.
Easy and faster to cook, with high efficiency.

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