What is an MCU?
What is an MCU?
An MCU (Microcontroller Unit) is an electronic component embedded in most modern electrical appliances like refrigerators and washing machines to control various functions. Essentially, it is a small computer designed to manage electrical devices. As such it is also sometimes referred to as a microcomputer or simply microcontroller.
For example, in a rice cooker equipped with an MCU, cooking begins with the press of a button. The MCU operates by receiving input, such as a button press, and generating an output, like initiating the rice cooking process.
MCU Applications
MCUs are integrated into most modern electronic devices, playing a crucial role in their operation. They are commonly found in household electrical appliances such as refrigerators, washing machines, rice cookers, microwaves, and vacuum cleaners. MCUs have also been widely adopted in industrial equipment like robots, loggers, thermometers, clocks, and even heated toilet seats. By controlling a wide range of electronic devices around us, MCUs have become an indispensable part of everyday life.
History of MCU Development
MCUs emerged from the need to miniaturize electrical devices and shorten design times. Before the 1960s, control circuits for these devices were built using individual transistors. A type of semiconductor primarily used as a switch, transistors can also be used to form amplification circuits, logic circuits, and arithmetic circuits that make up control circuits. These control circuits allowed the development of systems where electrical devices could be operated with the press of a button. However, one drawback was larger circuit sizes.
In the late 1960s, ICs incorporating transistors were introduced, enabling the miniaturization of control circuits. During this time, electrical devices were becoming increasingly widespread. However, the control circuits and ICs used in these electrical devices were custom designed for each product, requiring substantial time and cost for development.
To overcome these challenges, MCUs were introduced in the 1970s that allowed operation modifications through software. Although adoption took some time, MCUs provided a major advantage - they eliminated the need to for extensive IC redesign, greatly reducing the time and cost required for the development of control circuits and ICs. With the advent of MCUs, efficient control of various electrical devices became possible, contributing to the advancement of technology and enriching everyday life.
Benefits of Using MCUs
A key advantage of MCUs is their ability to combine multifunctionality and miniaturization while remaining adaptable to a wide range of applications.
Greater Miniaturization
An MCU is an LSI (Large Scale Integrated Circuit) that incorporates numerous electronic components like resistors, capacitors, and transistors into an ultra-compact form factor. Previously, electronic devices relied on multiple discrete components, resulting in large, bulky circuits. By integrating these components in a single chip, MCUs enable signficant device miniaturization.
Multifunctional
Integrating components allows additional functions to fit into a device. In the past, adding new features resulted in larger sizes. However, adopting MCUs has made it possible to integrate more functions, enhancing both multifunctionality and performance.
Adaptable to a wide range of applications
MCUs are also characterized by the ability to modify operations through software. Previously, altering functionality required redesigning the LSI, which was both time-consuming and costly. Utilizing MCUs allows for flexible process changes, shortening the time required to design and develop control circuits and ICs across a wide range of applications.
As highlighted in the history of MCU development, their miniaturization and versatility have led to widespread adoption in modern electrical devices.
The Role of MCUs in Refrigerators
Let’s explore how an MCU operates in a refrigerator.
A refrigerator's key functions can be summarized as follows.
① Maintain a constant internal temperature
② Light up the interior when the door is opened
③ Sound a buzzer if the door is left open for 60 seconds
The MCU functions as the command center to execute these tasks.
To maintain temperature ①, the MCU activates the compressor to cool the interior if the temperature is too high. Once the temperature drops to a certain level, the compressor is shut off.
For lighting control ②, the MCU detects when the door is opened using an ON/OFF switch that turns the light ON accordingly.
To sound the buzzer ③, the MCU measures the time the door remains open, triggering an alert after 60 seconds.
Manually managing the temperature, lighting, and alerts in a refrigerator would be impractical. Instead, the MCU efficiently automates these functions, ensuring smooth operation.
Inside an MCU
Structure of an MCU
An MCU consists of three main sections:
1) An input section that receives external signals such as button presses.
2) A processing section for processing received data.
3) An output section, which sends signals to external components like heaters and motors.
As illustrated in the diagram, MCU operation involves receiving input from push buttons or sensors, processing the data internally, and then outputting control signals to devices such as heater or motors.
Another feature is that the processing itself can be flexibly modified through software.
