We control the microwave: from mechanical twists to control from a smartphone

It's easy to cook or reheat food in a microwave oven. You need to load food, adjust the operating mode, and then press the "Start" button. The microwave oven will do the rest by itself in accordance with the commands of the control board. How the microwave control works, and what options for its execution are - we will consider in the material.

The principle of controlling the operation of the microwave oven

The control unit is responsible for the operation of the microwave oven in various modes. It includes a control panel as well as a mechanical or electronic controller. The main task of the unit is to maintain the set power and turn off the furnace after a certain time. That is, any control system must have two functional units: a power regulator and a timer.

The operation of the microwave is controlled either by a mechanical actuator or by its modern electronic counterparts. The choice of modes and operating parameters is set by means of the control unit.

In microwave ovens (with the exception of inverter models ), the heating power is regulated by pulse operation of the magnetron, that is, by turning it on and off during cooking. Due to the alternation of cycles of operation and downtime in the oven chamber, the required level of exposure to microwave waves on products is achieved.

Pulse operation of the magnetron is provided by the power regulator, which, according to the timer commands, switches the power supply circuit of the magnetron. The timer opens the power supply after a user-specified time. A simplified pulse control scheme is shown below.

The situation is completely different with inverter models. In them, the magnetron is constantly on, and the power of its radiation is regulated by the inverter during the cooking cycle. At the beginning of the cycle, cooking occurs at maximum power, which gradually decreases as the food is cooked.

Types of control units

Different control units have been used in microwave ovens over the years. Let's consider the device of each of them.

Mechanical control box

The very first variety that appeared with the first models of microwave ovens. It consists of two round knobs for setting the operating mode. One is responsible for the choice of power, the second for the duration of the operation.

One actuator is physically connected to the power regulator, the second to the timer. Each of the mechanisms has a pair of contacts for switching the primary supply circuits of the magnetron.

Mechanical control is simple to implement and cheap to implement, but it does not guarantee accurate operation. The user makes the setting of time and power, as they say, "by eye", being guided by the scale printed on the body of the device. Therefore, errors with setting the time ± 1-2 minutes are not uncommon (especially with a long cooking cycle).

Electronic control unit with encoders

The next stage of development was the emergence of electronic control units with encoders. Visually, these are the same "twists", but they no longer have a physical connection with the actuators. On the regulator shaft, sensors are installed that track the angle of rotation of the handle and transform it into a binary digital signal.

There may be several options for the encoder:

• with mechanical contact closure;
• optocoupler-based devices;
• Hall effect sensors.

Let's consider the principle of operation of the unit using the example of an optical encoder. By the way, it is quite often found in the mechanism of the computer mouse wheel, making it a serious competitor to mechanical encoders. The logic of operation of other types of encoders is identical to that described below.

The principle of operation is quite simple. In the process of rotating the handle, short impulses are formed, they are counted and converted into specific values ​​of the parameters displayed on the microwave screen.

https://www.geogebra.org/m/tdazuaq9

https://www.geogebra.org/m/kutkh9qm

https://www.geogebra.org/m/fwkqaebk

https://www.geogebra.org/m/t2cmgxdq

https://www.geogebra.org/m/gb6r2whr

The formation of impulses is as follows. The light emitted by the source passes through the chopping disk and is captured by the receiver. The main trick is in the interrupt disk. It has on its surface many windows located on its circumference.

The light beam is constantly interrupted during the rotation of the disk, as a result of which the receiver of the light signal captures a series of short pulses that are formed at the output of the encoder.

The slots in the disc are trapezoidal. This is done on purpose as a pair of signal receivers are used to detect the rotation of the encoder knob. The width of the window in the upper part of the disk is slightly wider, so the light is captured by the upper receiver a little faster than by the lower one. As a result, fixed pulses are formed at the terminals of the two receivers. They are the same in size, but somewhat shifted in time relative to each other.

It is this displacement that indicates to the processor in which direction the handle rotated with the encoder attached to its shaft. On the microwave screen, the user will see an increase or decrease in the value of the parameter being set.

Electronic control with buttons

In principle, the control of operating modes using buttons is not much different from the version with encoders. The differences can be seen visually: there are no rotating handles on the control panel, it is occupied by buttons designed to select a mode or parameter.

Physically, each button is a pair of spring-loaded contacts that close when pressed.

Touch control

The most advanced type of control to date. The touch panel microwave oven looks modern and even futuristic.

The touch panel has pictograms under which the touch sensors are hidden. Touching them changes the electrical capacitance of the medium around the sensor and triggers it.

The logic of controlling the microwave oven using the touch panel is not much different from other electronic control methods. To a greater extent, it depends on the software part than on the hardware solutions.

For a complete understanding of the principle of operation of the touch button, we suggest watching a short tutorial video.

Due to the need for additional components, touchpads are the most expensive solution. Some not the most conscientious manufacturers try to pass off key control panels as touch panels. Visually, this may still work, but the very first touch of the panel will put everything in its place.

Advanced microwave control

In recent years, the technology of controlling kitchen appliances using a smartphone has been actively developing. Microwaves have not been left out of progress. The brochures and demos are full of information about good governance. Select a program, set the required power level and cooking time, start the process - all this can be done from the mobile application. The main thing is that the oven and smartphone are connected to the same network.

However, so far the prospects for such management are in serious doubt. After all, this is about cooking, not about controlling a robot vacuum cleaner. You will still have to put dishes with food in the chamber, and after cooking or warming up, remove them. So what prevents the user, being near the microwave, to turn it on with his hands? The booklets do not provide an answer to this question.

Of greater interest is learning how to work with a microwave in the application and the ability to create your own cooking algorithms when the recipe involves the use of microwaves, grill, and convection in a certain sequence. In this aspect, the ability to create and save cooking recipes is an undoubted step forward!