How to find out touch switch for sale capacitive online?

25 Nov, 2021

By hqt

Touch switch for sale capacitive is the keyboard where we select the oven control functions. It forms by two sheets of polyester separated by a plastic spacer. There are graphite contacts on the blades.

Moreover, when you press a key, the graphite of the front blade touches that of the rear blade and thus triggers that function. Below we see the physical aspect of this component and the internal structure:

touch switch for sale capacitive

The membrane differs from one oven model to another. It does the rest of the touch switch, but they all work on the same operating principle.

This component is one of the most defective in microwaves, ranging from the breakage of the flat cable due to dryness to the wear of the graphite due to misuse or excessive use.

How the cold and hot test should be done on touch switch for sale capacitive?

Cold is more work and consists of holding down a key. And measuring the pairs of terminals two by two on touch switch for sale capacitive until you find one that the pointer indicates less than 1K. If the pointer does not move any pair with the key pressed, the membrane is defective.

When hot, do the following: Connect the hob to the oven without the membrane. Don’t forget to turn off the AT transformer primary. Plug the oven into the socket. And with a piece of wire touch each two terminals where the keyboard tape fits. If the functions being activate, the board is good and the membrane must replace.

touch switch for sale capacitive 2021

Moreover, the membrane is self-adhesive to the oven panel and before sticking it in its final position; we must fit touch switch for sale capacitive into the connector without removing the backing paper and press the keys. If these obey the commands, you can detach and paste it permanently. If it doesn’t work, we must change the membrane where we purchase it.

What do you know about mechanical timer?

The old microwaves controlled the food preparation time through a switch coupled to a reduction motor. The motor-key set is called “mechanical timer”. Current ovens have an electronic circuit located on a printed circuit board behind the panel.

We see touch switch for sale capacitive in a modern microwave oven

On this board there is an IC called a microcontroller. As its name implies, it controls all microwave functions. For instance

  • cooking time,
  • defrosting,
  • clock, etc.

And lights up a display that can be fluorescent or liquid crystal.

What are the main defects of touch switch for sale capacitive?

In this section we will talk about the main components and defects of the touch switch for sale capacitive.

Touch switch power supply; function

Its function is to supply the DC voltages necessary for supplying the touch switch. The power supply is easily found on the touch switch through the transformer, 4 diodes and the filter capacitor.

 Generally, the board source supplies the following voltages: 12 or 24 VDC for the relays, 5 V for the micro IC and 2 or 3 VAC to light the fluorescent display filament. If the oven uses liquid crystal display there will be no filament voltage.

Touch switch transformer: Capacity

Also called “trafinho”, this small transformer receives 110 or 220 V from the mains and supplies two voltages on the secondary: one of 12 or 24 V and another of 3 V for the filament of the fluorescent touch switch for sale capacitive.

Physical appearance and symbol of touch switch for sale capacitive:

To test this cold transformer, use the X1 scale, measure the primary pins, the pointer should indicate between 100 and 500 Ω, the secondary pins 24V, the pointer should indicate a little more than 10 Ω and the pins of the 3V secondary, the pointer should indicate less than 10 Ω.

 If the pointer does not deflect on some of the windings, the transformer is burned out and the touch switch will not work.

How the transformer test is performed?

A switch is a special resistor that changes resistance when the voltage across its terminals changes. On the touch switch for sale capacitive there is a switch connected in parallel with the transformer. The switch is specified by its voltage limit. For 110 V ovens, the switch can be 150 or 175 V.

For 220 V ovens, the switch is 300 V. Under normal operating conditions, its resistance is very high. When the mains voltage goes above the nominal value, the switch resistance decreases and it dampens the voltage peak in the primary, preventing it from burning out.

When the mains voltage exceeds the switch limit, it burns (shorts out) and opens a path that feeds the transformer, turning off the furnace immediately. Therefore, the switch works as a protection device for the plate transformer.

What it looks like and how to test this component on X10K?

The relay is a magnetic switch as touch switch for sale capacitive that is, activated by a coil. Further, the furnace has at least two relays on the touch switch: one of them, the larger one, to feed the AT transformer and another smaller one to feed the motors and the lamp.

How relay drives?

Each relay drives by two transistors that receive a drive voltage at the base coming from one of the micro IC pins. Moreover, below is an example in which a “Sharp” microwaves uses a drive circuit.

What is the role of protection center?

These circuits turn off the oven in case of an internal short circuit or overheating and also prevent the oven from operating with the door open. It makes up of fuses and micros witches activated by the door latches.

Below we see a circuit used to power the AT transformer and the touch switch for sale capacitive of a “Sharp” microwave. Moreover, the components of the protection circuit are indicated by red arrows:

The common fuse turns off the oven in case of a short circuit in the AT source. In addition to, the thermal turns off the oven in case of excessive heating and the keys prevent the oven from working with the door open.

What is the function of a microwave fuse?

This fuse can have a glass or porcelain body and its current limit is 15 A in 110 V ovens and 10 A in 220 V ovens. It connects in series with the oven power supply. Below we see some aspects of this component and the way to test it at the scale of X1:


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