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What Is a CMOS Sensor?

A CMOS sensor is an image sensor used in digital cameras and other photographic equipment. The light received by the individual photodetectors is converted into an electric charge, which is then passed through an amplifier circuit composed of CMOS and extracted as a voltage or current according to the intensity of the light.

In the past, CCD sensors were used as the mainstream image sensor, featuring a structure in which the charge is transferred by the CCD and converted to a voltage via a floating diffusion amplifier (FDA).

CCD sensors have advantages over CMOS sensors in terms of sensitivity, signal-to-noise ratio, and low dark current, but they have disadvantages in terms of complex power supply configuration, unavoidable smear generation, and the fact that the manufacturing process is special and general CMOS LSI production equipment cannot be used. Recently, CMOS sensors have become the mainstay of image sensors due to advances in methods for reducing the effects of dark current and improving the signal-to-noise ratio in CMOS sensors.

Uses of CMOS Sensors

In the past, CMOS sensors were used in cameras mounted on smartphones and tablets because of their low cost of production. On the other hand, CCD sensors with low noise were mainly used in single-lens reflex cameras and video cameras, which require high image quality.

However, as noise reduction methods for CCD sensors evolved, the smear and blooming that had been a problem with CCD sensors did not occur, and the CCD sensor was gradually replaced by the CMOS sensors. CMOS sensors are now used as image sensors in all types of photographic equipment.

Principle of CMOS Sensors

The basic function of an image sensor is to store and transfer the electric charge generated by the light-receiving elements arranged in large numbers on its surface, convert it into a voltage or electric current, and output it. In this respect, CCD sensors and CMOS sensors share the same function.

The major difference between the two lies in the charge transfer mechanism: CCD sensors have a grid of photodiodes as light-receiving elements, and charge can be temporarily stored in the N-type region of these photodiodes.

A vertical CCD is placed adjacent to these photodiodes, and all the charges accumulated by each photodiode at a given time are simultaneously transferred to the vertical CCD. The charges are sequentially transferred and delivered to the horizontal CCD.

The horizontal CCD transfers the charge transferred from the vertical CCD to the FDA, which outputs a voltage corresponding to the amount of charge, thus providing a voltage output corresponding to the intensity of the light irradiating the photodiodes. As described above, in a CCD sensor, the amount of charge from all photodiodes is output sequentially.

On the other hand, CMOS sensors have a photodiode, an amplifier that amplifies the output of the photodiode, and a switch element that connects the amplifier output to the signal line, so that light reception, conversion, amplification, and output are performed for each photodiode.

From this configuration, CMOS sensors can specify individual photodiodes by combining horizontal and vertical scanning signals and can extract voltage or current according to the amount of charge. Thus, any photodiode can be selected and its signal be read out.

Due to these structural differences, CMOS sensors have the advantage of high-speed readout by limiting the signal to the necessary area and eliminating the transfer noise of CCDs. Furthermore, while CCD sensors inevitably suffer from smears caused by noise components flowing into the CCD, this is not the case with CMOS sensors.

CMOS Sensors Structure

CMOS sensors combine a photodiode, which is a light-receiving element, with an amplifier and switch elements, and integrate many of these elements. The photodiode manufacturing process is special and different from that of transistors, but the other components are identical to those of CMOS LSIs, so the use of CMOS manufacturing equipment is advantageous over CCDs.

New developments are also emerging about photodiode placement. In this structure, photodiodes are placed on the backside of the CCD, whereas circuits such as amplifiers and switch elements are formed on the front side. The photodiode is connected to the circuitry via internal wiring. Although the manufacturing process is more complex, the photodiodes can be placed with no gaps between them, which improves light collection efficiency.

The circuitry in CMOS sensors operates with a single power supply, so basically only a single power supply of about 3.3 V is required. CMOS sensors have an advantage in terms of power consumption.

Other Information on CMOS Sensors

1. CMOS Sensors Market share

Sony had a dominant market share when CCD sensors were at their peak, but now that CMOS sensors have become the mainstay and their primary application has shifted to smartphones, Sony’s market share is gradually declining. In 2021, Sony’s market share in terms of value will be 45%, Samsung’s 26%, and OmniVision’s 11%, according to the survey.

2. Size of CMOS Sensors

CMOS image sensors are available in a variety of sizes, from large to small. Taking Canon’s CMOS image sensors as an example, there are six different sizes of image sensors.

• 35mm full size (approx. 36mm x 24mm)
• APS-H size (approx. 29 mm x 19 mm)
• APS-C size (approx. 22 mm x 15 mm)

However, they are not sold to the general public and are limited to use for their cameras.

• 1 inch
• 2/3 inch
• 1/1.8 inch

Generally, for the same number of pixels, the larger the sensor size, the better the image quality. Also, the wider the aperture, the higher the sensitivity.

What Is an LED Driver?

An LED driver is an integrated circuit (IC) that stably drives and safely controls LEDs. LEDs emit varying amounts of light depending on the current value, and the current value varies depending on the color of the LED, so stable driving requires highly accurate current control. For this reason, control by a constant-current circuit is extremely important, and this is the main function of the LED driver.

Uses of LED Drivers

As the name suggests, LED drivers are used to drive and control LEDs. In recent years, however, LEDs with low power consumption and long life have become the mainstream for lighting fixtures instead of fluorescent lamps, and many LED drivers are sold for lighting applications.

Lighting fixtures often require brightness control, and especially in the case of LED drivers, strict current control is important. Recently, there have been many needs to switch to LEDs for lighting from the viewpoint of promoting energy conservation, as typified by the SDGs, which also require highly efficient lighting.

In addition, LEDs are also being used as indicator lamps in home appliances and automobiles, and LED drivers dedicated to these applications are being developed.

Principle of LED Drivers

LED stands for “Light Emitting Diode” and refers to a semiconductor device that emits light when a forward bias is applied to its PN junction. The LED drivers incorporate a constant-current generation circuit integrated on an IC, and depending on the product, a PWM control circuit, and SPI or I2C interface are also built-in.

In general, the amount of light emitted by an LED varies with the amount of current applied, but the color (emission wavelength) of the LED also changes by the current value. In addition, too much current will have a significant impact on the life of the device. Therefore, it is necessary to accurately control and apply the optimum current value for the LEDs used, taking into consideration the light intensity, hue, and luminous efficiency according to the luminous characteristics of the LEDs, and LED drivers are used for this purpose.

For single-function LED drivers, a combination of discrete Zener diodes, MOSFETs, etc. can be used, but when multiple LEDs are connected in series or parallel and LEDs of various colors with different optimum current values are to be operated in combination, ICs are used to meet the required specifications. 

Other Information on LED Drivers

1. Driver Format of LED Drivers

There are various types of drivers used in LED drivers, such as linear type and step-up/step-down type.

Linear Type
This circuit type does not incorporate a DCDC converter but uses a MOSFET and resistors for constant-current control. The single function allows for miniaturization and cost reduction but has the disadvantage of high MOSFET loss at high input voltages.

Step-Up/Step-Down Type
This circuit type can operate with high efficiency by suppressing the increase in loss during the step-up and step-down functions that can accommodate an increase in the number of LED stages. However, since the circuit is complex and the cost is high, LED drivers that can only support boost or buck are also widely used, depending on the application.

2. PWM Control

PWM control is widely used in LED drivers for dimming. This is because the method of adjusting the driver’s DC current value has problems with heat generation due to lower efficiency and wavelength change (emission color change) accompanying the current change.

In the case of PWM-control led drivers, the apparent voltage can be varied by adjusting the width of rectangular pulses (duty ratio), and there is no power loss associated with dimming. In such a driver, LED dimming is often performed with a semi-fixed resistor. If the semi-fixed resistor is removed and replaced with a volume, LED drivers that can be adjusted with the volume can be realized.

The brightness of LEDs is proportional to the duty cycle of the pulse, but if the ON/OFF cycle is too slow, it can be discerned by the human eye, leading to flickering of the lighting. Therefore, care must be taken with the set frequency of the PWM control.

3. Serial Interface

It is common for several LEDs of different colors to be used in home appliances and automobile instrument panels. Depending on the type and quantity of LEDs to be controlled, IC connection may be difficult if only analog signals for ON/OFF and bias values are exchanged. In such cases, a serial interface with digital control over a few wires, such as SPI or I2C, is used.

LED drivers with serial interface functionality include large-scale products capable of controlling several hundred LEDs simultaneously, as well as products capable of controlling brightness and diagnostics for each channel.

What Is an Isolation Amplifier?

An isolation amplifier is an amplifier that can transmit signals while providing electrical isolation between input and output signals.

Isolation amplifiers are incorporated into the input and output circuits of printed circuit boards, such as microcontroller control boards, to provide DC isolation from incoming signals and enable accurate measurements. For this reason, they are generally used in measuring instruments and medical equipment.

They also serve to ensure the safety of users. Features include prevention of electric shock, signal branching, countermeasures against high ground potentials, and noise suppression.

Uses of Isolation Amplifier

Isolation amplifiers protect power supplies by removing reverse currents caused by high ground potentials. They can also be installed in environments with many noise sources.

Specific applications are as follows:

• Train Cars
  Monitoring of overhead line voltage and current, monitoring of drive power systems, control signal interfaces between trains, etc.
• Power Generation Equipment
  Interface between power generation and control units, monitoring of terminal voltage of each battery cell and solar cell connected in series, transmission of power conditioner control signals, etc.
• FA-Related
  Interfaces between sensors and control devices, control signal transmission for large power supplies, etc.
• Others
  Medical equipment, semiconductor manufacturing equipment, communication equipment, measuring equipment, etc.

By incorporating them into key locations in circuits, they function as safety measures to prevent users from receiving electric shocks in the event of equipment malfunctions.

Principle of Isolation Amplifiers

An isolation amplifier is a type of amplifier that operates circuits while completely separating and isolating them so that the circuits are not affected by grounding or common power supply. The main signal transmission methods include optical, magnetic, and capacitive, of which the operation of the magnetic method is as follows.

The input signal to the Isolation Amplifier first enters a buffer amplifier1 on the input side. This amplifier has the characteristics of high input impedance and low output impedance. The output side of the Isolation Amplifier is a similar buffer amplifier 2.

There is an isolation circuit between the two buffer amplifiers, but the input side is completely isolated from the output side in terms of DC. The isolation circuit has a signal transformer, with switching elements connected to the primary and secondary coils, respectively. synchronous rectification is possible by repeating the two switching elements on and off simultaneously.

Synchronous rectification then transfers a voltage to the secondary equal to the signal voltage entering the primary. Therefore, even if the primary and secondary sides of a signal transformer are completely isolated, the signal can be taken out from the secondary side.

Characteristics of Isolation Amplifiers

An isolation amplifier has the following features.

• No leakage of current from the output side to the input side, so there is no risk of electric shock and safety can be ensured.
• Since it operates even when a high voltage exists between the input and output, signal amplification of the high-voltage section is possible.
• Operates even in the presence of extremely large noise between input and output, enabling common-mode noise elimination.
  High withstand voltage. (Many products are several thousand volts)

Other Information on Isolation Amplifiers

1. Power Supply for Isolation Amplifier

Isolation amplifier isolation transformers have a power transformer in addition to the signal transformer. On the primary side of the power transformer, a square wave from the oscillator is added, and the same square wave is generated on the secondary side.

The oscillator frequency is set to match the frequency response of the Isolation Amplifier: a square wave oscillator of about 50 kHz to 100 kHz. The voltage from the power transformer drives the switching elements on both the primary and secondary sides, respectively.

The primary and secondary sides of the power transformer are also isolated from each other DC-wise, and the power supplies for the primary and secondary buffer amplifiers are also supplied from the primary and secondary sides of the power transformer.

2. Photocoupler for Isolation Amplifier

When an isolation amplifier signal transmission is optical, a photocoupler is used. This photocoupler is an optical IC used in Isolation Amplifier circuits when making an isolated circuit in which the input and output are completely floating above each other, or when detecting signals of different potentials.

What Is an Air Ionizer?

An air ionizer is a device that removes static electricity generated at manufacturing sites, etc., which can cause machine malfunctions. An air ionizer is also called a static electricity eliminator or slow electricity.

An object charged with static electricity has an imbalance between positive and negative electricity. The air ionizer strikes the charged object with static-charged particles (ions).

In this way, the principle of the air ionizer is to change a charged object into an electrically balanced state, i.e., a state without static electricity. Specifically, air ionizer is used to prevent foreign objects from adhering to food trays and cups by eliminating static electricity inside them, and to prevent static electricity destruction in camera modules.

Types and features of Air Ionizers

This section describes the types and features of air ionizers. Air ionizers generally have evaluation items such as static elimination speed and ion balance, but there are several types in the principle of how ions are generated from the ionizer.

1. Voltage-Applied Method

There are several types of air ionizer methods, including the corona discharge method, which irradiates ions generated by corona discharge, the soft X-ray method, which irradiates weak X-rays, and the radiation method, which irradiates α-rays and β-rays, but the corona discharge method is most commonly used for safety and economic reasons.

The electrostatic remover (device, etc.) is charged positively or negatively, and there are two types of ion irradiation methods: the AC method and the DC method.

Corona Discharge

Corona discharge is a discharge phenomenon that occurs when a high voltage is applied to a thin local area, which produces ions. Corona discharge air ionizers utilize this principle to intentionally generate ions, which are then irradiated to remove static electricity.

AC Method

A single discharge needle alternately generates positive and negative ions. This method uses the AC voltage from the outlet as it is, and has a good ion balance, but is characterized by a slow static elimination speed.

DC Method

This method generates positive/negative ions from each of the two discharge needles. Since DC voltage is continuously applied, the ion polarity is either positive or negative.

2. Types by Application

There are four types of air ionizers for different applications. Therefore, it is necessary to consider the installation environment and conditions and select the most effective type.

Bar Type

This is a bar-shaped air ionizer. It is suitable for high-speed static elimination over a wide area and has the highest basic performance.

Spot Nozzle Type

This type of air ionizer removes static from a small area through a nozzle. Its small size enables pinpoint ionization of small areas.

Fan Type

This type of air ionizer uses airflow generated by a fan to spray out ions. The static elimination range is narrower than that of the bar type, but it is compact and can be used on a tabletop.

Gun Type

This type of air ionizer emits ions in combination with compressed air. In addition to static elimination, it can also simultaneously remove foreign matter adhering to surfaces.

How to select Air Ionizers

There are three main factors in selecting air ionizers: static elimination distance, static elimination range, and static elimination speed. Since each type has different characteristics, it is necessary to carefully consider the relationship between the object to be ionized and the air ionizers.

1. Elimination Distance

The static elimination distance is the distance that the air ionizers can eliminate static from the object. For example, spot nozzle-type air ionizers have a small static elimination distance due to their small size, while bar-type air ionizers can eliminate static at a distance of 1 m or more.

2. Static Elimination Range

The static elimination range is the length of the width direction that the air ionizers can eliminate static. Bar-type air ionizers can eliminate static over 1 m, while blower-type air ionizers can eliminate static over less than 1 m. Therefore, it is necessary to consider how large an area is to be ionized.

3. Ionizing Speed

The static elimination speed is a performance indicator of how long it takes an air ionizer to eliminate static. The shorter the speed, the higher the performance of the air ionizers.

What Is Cleaning System?

A Cleaning System is a device that uses chemical and physical properties to remove unwanted substances from the surface of materials.

It is used in the manufacturing process of precision equipment, semiconductors, displays, among others. When not used correctly, Cleaning Systems can lead to an increased incidence of defective products and reduced yields!

Cleaning methods vary from ultrasonic cleaning, spray cleaning, brush cleaning, dry cleaning, and solvent cleaning. In the case of semiconductor manufacturing, there are more than 500 manufacturing processes, of which the cleaning process is said to account for 30% to 40%.

Applications of Cleaning System

Examples of specific uses of Cleaning System are as follows:

• Cleaning silicon wafers in the semiconductor process.
• Cleaning of dirt adhering to metal filter mesh.
• Removing metal dust adhering to metal surfaces after cutting.

Cleaning System is selected based on the type of contamination, size of the cleaning target, cleaning time, and cleaning accuracy. Also important are the cleaning method, cleaning agent used, and drying method.

Principle of Cleaning System

In the case of semiconductor processes, the role of cleaning is to remove contamination from wafers. Contaminants include small invisible debris called particles, organic matter contained in human grime and dandruff, oil and grease such as sweat, and contamination from metals used in the factory.

Cleaning System washes these contaminants away with solvent or pure water. However, the process doesn’t conclude with cleaning alone. An essential step is drying, commonly referred to as “dry-in/dry-out.” Wafers must undergo thorough drying before being removed from the equipment.

Typical Cleaning Systems include ultrasonic cleaning, spray cleaning, brush cleaning, dry cleaning, and solvent cleaning.

1.Ultrasonic Cleaning System

Ultrasonic Cleaning Systems are used to clean wafers by placing the object to be cleaned in a chemical solution and vibrating the inside of the object with ultrasonic waves. The magnitude and frequency of the vibration are selected according to the object to be cleaned. 

2.Spray Cleaning System

Spray Cleaning System is a method of cleaning objects by spraying gas or liquid from a nozzle. Handheld Cleaning Systems are also available and can be used for cleaning large objects.

3. Brush Cleaning System

Brush Cleaning System uses brushes to remove contaminants, and then rinses them away with a solution or spray washer. Since brushes are used as a physical method of cleaning, they can clean difficult-to-remove contaminants.

4. Dry Cleaning System

Dry Cleaning System irradiates UV (ultraviolet) light onto the object to be cleaned to generate ozone and active oxygen, which react with the contaminant to remove it. This method is mainly used in the manufacturing of semiconductors and displays. 

5. Solvent Cleaning System

Solvent Cleaning System dissolves and removes contaminants by utilizing the dissolving power of solvents. Care must be taken because extremely hazardous solvents may be used.

Structure of Cleaning System

The basic structure of a Cleaning System consists of a conveyor system, a processing tank, a pure water tank, and a drying stage. The conveyor system is used to carry in and out objects, and the cleaning system cleans the objects in the processing tank. The pure water tank is used to wash away the chemicals adhering to the object, and the drying stage is used to dry the object.

In principle, only one type of contamination can be cleaned with one type of treatment solution, and multiple treatment tanks and pure water tanks are required when multiple types of contamination are to be cleaned. In the semiconductor manufacturing process, two types of equipment are used: batch-type equipment that processes multiple wafers at once, and single-wafer equipment that processes wafers one at a time.

In the batch type, wafers are placed together in a case called a carrier, and each carrier is placed in a processing layer for cleaning. The single-wafer type performs spray cleaning while rotating the wafers one by one.

Other Information on Cleaning System

Cleaning Agents Used in Cleaning System

Cleaning semiconductors involves the use of multiple processing liquids. Each treatment solution removes different contaminants. Each treatment is followed by rinsing with pure water.

SPM
A mixture of sulfuric acid and hydrogen peroxide for removal of organic matter.
APM
A mixture of ammonia and hydrogen peroxide to remove particles and organic matter. In addition, ultrasonic waves are added to increase the particle removal rate.
DHF
A mixture of hydrofluoric acid and pure water to remove metals and oxide films. Since hydrofluoric acid is a strong acid and dissolves silicon, it is diluted with pure water and used to treat only the wafer surface.
HPM
A mixture of hydrochloric acid and hydrogen peroxide is used to remove any remaining metal and oxides, creating a passivation layer on the surface to prevent re-deposition of contaminants.
Finally, the wafers are rinsed with pure water and undergo a drying process.

What Is a Digital Timer?

A digital timer is a device that automatically switches itself on and off after a preset period.

Digital timers can be either analog or digital. Compared to analog timers, which are set manually with a dial scale, digital timers can be set more precisely with numerical values. In this case, the control accuracy is higher, but the setting method is slightly more complicated than for analog timers.

Uses of Digital Timers

Digital timers are used in a variety of situations. By installing a Digital Timer on a device that is to be operated for a certain period, it is possible to stop the movement of the device at any desired time.

1. Applications in the Manufacturing Field

Digital timers used in the manufacturing field are characterized by their high accuracy and multiple functions as they affect product quality and stability. In general, the more advanced the functions, the more expensive the price, ranging from several thousand yen to several tens of thousands of yen per unit.

Prices vary depending on performance, such as flicker operation, one-shot output, on-delay and off-delay control, and interval function.

2. Applications in the Sports Field

Digital timers used in the field of sports are characterized by large products and high visibility that can be seen by spectators. Digital Timers with a real-time display function are often used, but for sports that require precise time measurement, such as track and field events, products with sensors at the start and finish line to measure times automatically are also available.

Principle of Digital Timers

Digital timers can be automatically turned on and off. Understanding the use and principle of the function for each application will help you use them more effectively.

Digital timers receive a signal sent from the input portion of the device and measure a predetermined time. When the predetermined time elapses, an output signal is issued to stop or start the machine.

Types of Digital Timers

There are four main types of digital timers, classified according to the type of control. 

1. Digital Timer With On-Delay Control

On-delay control is a control method in which the contact turns on after a set period has elapsed, and then waits a little longer before starting to operate. While this has the advantage that the contacts are immediately restored by cutting the voltage, there is a time lag between the switching of the contacts and the activation of the device.

Push-button traffic signals, for example, operate by gaining additional elapsed time from the timer time using on-delay control. 

2. Digital Timer With Off-Delay Control

Off-delay control is a control method in which operation begins immediately after the contacts are switched. While the advantage is that there is little time lag before the device is activated, it takes time from contact switching to recovery.

Lighting that is automatically turned on by a motion sensor, for example, is often operated using off-delay control. 

3. Flicker-Operated Digital Timer

Flicker operation is an operation that repeats on and off at a fixed cycle. There are two types of flicker operation methods: “flicker off start” in which the output starts from off and repeats off, on, and off, and “flicker on start” in which the output starts from on and repeats on, off, and on.

This can be used in cases where it is necessary to switch on and off at regular intervals, but the time at which on and off are switched is the same set time. If you want to set them at different times, you will need to select a device with a twin timer function.

This function is often used to send periodic signals and notifications, and is used in familiar situations, such as traffic signals, flashing signals, and buzzer interrupting tones. 

4. Digital Timer With Interval Operation

Interval operation is an operation in which the output turns on as soon as an input is made to the timer and turns off after a set period of time. By setting the time in advance for the output to go from on to off, the device can operate without deviation from the set time.

There are two types of triggers to turn on an output: power start and signal start. Practical examples of interval operation include amusement park applications.

What Is a Power Supply System?

A power supply system is a device that converts an AC power source, such as an electrical outlet, into a stable DC power source.

AC power sources such as electrical outlets, whether for industrial or residential use, are high voltage and cannot be used for electronic equipment as they are. Therefore, it is necessary to convert the voltage to a DC voltage suitable for the equipment.

Power supplies are generally classified into two types: switching type and transformer type, but switching type is currently the mainstream due to its small size, lightweight, and high efficiency.

Uses of Power Supply Systems

As the name suggests, power supply systems are a device used to supply power. Since they are used to convert AC power to DC voltage suitable for electronic equipment, they are built into almost all electronic equipment found in every home.

It is used in every electronic device so that when you connect a cable to a wall outlet, you might expect to find power supply systems on the other end of the cable.

Since it is a device that can regulate voltage, power supply systems can provide power voltage without the need for a transformer.

Principle of Power Supply Systems

In a transformer-based power supply system, the AC power supply system voltage is transformed to an appropriate voltage by a transformer and rectified to DC by a rectifier. The rectifier rectifies the rectified voltage to DC, which is then smoothed by a capacitor to supply a stabilized DC voltage.

In a switching-type power supply system, the AC power supply system’s voltage is converted to DC, which is then converted to pulsed high-frequency power by a high-speed switching circuit. This high-frequency power is rectified and smoothed using a transformer to obtain a suitable DC output voltage.

The transformer method can suppress noise to a small level, but it is large and heavy, and its power efficiency is poor. In contrast, the switching method can be highly efficient and lightweight, but it is noisier.

Since power supply systems cannot operate at 100% efficiency, losses are converted to heat, and heat is generated. The amount of heat generated is generally determined by the following equation:

Heat generation (W) = input power – output power = (output power/efficiency) – output power

If the amount of heat generated becomes too great, it may cause a drop in output power or a failure.

Other Information on Power Supply Systems

1. Making Your Power Supply Systems

Power supplies are simple in structure and can be made by the user. The materials required are resistors, smoothing capacitors, and diodes.

First, the receiving voltage is dropped by the resistor. Then, the diode is used to change it to a direct current. At this point, two diodes are required if full-wave rectification is desired.

Finally, a smoothing capacitor is connected in parallel with the load to complete the process. A resistor can be substituted for the transformer. The capacity of the power supply systems is determined by the capacitance of these individual parts. If multiple loads are to be connected, more capacity is required.

2. Small Power Supply Systems

Industrial power supplies are generally housed in control panels and are small enough to be attached to the panel. Currently, DIN-rail mounting is the mainstream.

In homes, power supplies are the AC adapters used to charge PCs and smartphones. They have been miniaturized and are now palm-sized. In audio equipment, power supplies are used for amplifiers. They are also palm-sized and can distribute power to as many as eight devices. 

3. Noise Caused by Power Supplies

In terms of audio equipment, power supply systems are a device that supplies power to effectors and other devices. Effectors are devices that add effects such as reverbs and low-pass filters to music. As a classification, they can be divided into analog and digital devices.

A single power supply system itself can supply power to any number of effectors as long as they are under the capacity. However, if analog and digital effectors are connected to the same power supply systems, noise will be generated.

The cause is the way digital effectors work. Digital effectors use electronic circuits to convert audio and electrical signals with choppers and other devices to create square waves. Square waves distort analog waveforms, resulting in audio noise.

To prevent noise, separate the power supply systems for analog and digital effectors. By electrically isolating them, noise caused by square waves can be eliminated.

What Is a Door Lock Switch?

A door lock switch is a device that produces a contact output when a door is opened or closed.

Widely used contact-type door lock switches are similar in construction to limit switches and microswitches, and are characterized by the fact that they are fixed to the door or doors.

Uses of Door Lock Switch Applications

Door lock switches are one of the most widely used devices in industry and household appliances.

Door lock switches are used in the following applications:

• Detecting the opening and closing of refrigerator and microwave oven doors
• Automatic lighting of barns
• Interlocking large presses and transport equipment
• Automatic lighting of control panels
• Detecting the opening and closing of trays in printers and multifunctional machines
• Automobile door open/close detection

The most common application is in refrigerators. Many refrigerators sound a buzzer if the door is kept open for a long period, or turn on internal lighting when the door is opened. In this case, door lock switches are used to detect the opening and closing of the door.

Door lock switches are also used as safety interlock devices in some industries. They are mainly used in large manufacturing equipment and are often installed to prevent personal injury.

Accidents involving large equipment and high-torque power equipment have been occurring more frequently than in the past. To prevent such accidents, we take measures such as covering the entire equipment with a safety fence. Since it is difficult for people to approach the equipment if only covered with a fence, a door is installed, and an interlock is often installed so that the equipment stops when the door is opened.

Door lock switches used for interlocks are sometimes called safety door switches. If the door lock switch alone is judged to be inadequate for interlocking, a door switch with an electromagnetic lock, etc., may be employed.

Principle of Door Lock Switch

A door lock switch consists of a contact, a mechanism, and mounting hardware.

1. Contact Point

The contact is a component that transmits a digital contact signal. Mainly materials such as silver and gold are used. The allowable current value of contacts is generally around several amperes, and they are often incorporated into control circuits. 

2. Mechanism Part

The mechanical part is a component that detects the opening and closing of doors. Depending on the application, there are contact-type products and non-contact-type products. Contact-type products mainly incorporate microswitches, while non-contact-type products incorporate reed switches. 

3. Mounting Brackets

Mounting hardware is used to attach the product to the door. Products with a structure such as screw fastening are common. Products using one-touch plugs are also available.

Types of Door Lock Switch

Door lock switches come in a variety of types, depending on the application.

Typical types are as follows:

1. Non-contact Door Lock Switch

Non-contact door lock switches are door switches with an internal reed switch. It comes with a dedicated actuator and uses a built-in magnet to detect the opening and closing of the door. Since it does not make contact with the door, it is characterized by the fact that it has a few parts that are subject to mechanical wear.

General reed switches can open and close contacts by using a magnet, but for safety applications, the structure requires the use of a dedicated actuator. This is to prevent malfunction of the reed switch.

2. Contact-Type Door Lock Switch

The contact type is a door lock switch with an internal microswitch. The door closing is detected when the actuator at the tip of the switch contacts the door. Various actuator types are available.

Because they are robust and inexpensive, contact-type door lock switches are used for refrigerator doors and printers. However, there is a risk of malfunction if the internal spring weakens with use over time.

Door Lock Switch With Electromagnetic Lock

Door lock switches with electromagnetic lock are a door switch that has the function of locking the door with an electromagnetic lock. If a door lock switch is used for safety purposes, a malfunction of the door lock switch may cause personal injury.

By selecting a door lock switch with an electromagnetic lock, it is possible to prevent accidental entry by locking the door. Generally, an interlock is provided so that the equipment will stop if the door is forced to be pried open when locked.

What Is a Signal Analyzer?

A signal analyzer is a signal measurement, evaluation, and analysis instrument that can detect even signals with complex modulation.

It can measure the amplitude versus frequency of an incoming signal over the entire frequency range of the instrument and the spectrum strength of known or unknown signals. It can also measure the amplitude and phase of an input signal at a single frequency within the instrument’s intermediate frequency (IF) bandwidth.

In addition to frequency domain spectrum measurements, signal analyzers are capable of advanced time domain analysis. The modulation quality of complex digitally modulated signals, such as cellular phones, can be analyzed using sophisticated signal analysis processing.

Uses of Signal Analyzers

Signal analyzers are used for frequency spectrum analysis, time-based signal analysis, and the evaluation of modulation signal quality.

1. Frequency Spectrum Analysis

Signal analyzers are used for frequency spectrum analysis. It is especially useful for evaluating ACLR (adjacent channel leakage power), which expresses signal distortion of digitally modulated waveforms.

Applications include testing RF characteristics of terminals and transmitting machines in digital radio systems. Specifically, they include carrier frequency, channel bandwidth, channel power, occupied bandwidth, and adjacent channel leakage power ratio.

In addition, it can measure spurious and harmonics over a wide frequency range from an RF band to a microwave band, which is a major feature of superheterodyne spectrum analyzers.

2. Time-Based Signal Analysis

Signal analyzers are also used for time-based signal analysis. The input RF signal is converted to a digital IQ data format, captured, and processed digitally at a high speed.

Therefore, it is effective for analyzing the PvT (Power vs. Time) waveform of each slot in 5G modulation. 

3. Modulation Quality of Digitally Modulated Signals

A signal analyzer is also used for evaluation of modulation accuracy EVM and CCDF (complementary cumulative distribution function) evaluation analysis, which are familiar in the world of mobile communications.

In addition to spectrum characteristics, the modulation quality of digitally modulated signals used in communication systems must be measured to maintain stable communication conditions. In this respect, signal analyzers can also measure the modulation quality of digitally modulated signals by combining it with various vector analysis applications.

Signal Analyzer Principle

The signal analyzer captures the memory of the measured signal for a certain amount of time, with only the frequency of the signal converted. Then, the system obtains analysis results through the steps of “digitizing and storing,” “converting frequency,” and “converting to spectrum, etc.”

First, the measurement signal entering the input section of the Signal Analyzer is converted to an intermediate frequency (IF) in the frequency conversion section. Next, the IF-converted measurement signal is converted to digital data. The digitized time-series waveform data is then immediately captured into the internal memory. This data can also be stored separately on a hard disk.

Signal analyzers have the advantage of high-speed processing and high repeatability. It is suitable for analysis and analysis of high-resolution standards such as millimeter wave (wavelength range from 1 to 10 mm) and sub-millimeter wave (wavelength range from 0.1 to 1 mm).

Other Information on Signal Analyzers

1. The Difference Between a Signal Analyzer and a Spectrum Analyzer

Signal Analyzer is a spectrum analyzer capable of analyzing modulated signals. Specifically, Signal Analyzers are very advanced in time-based signal measurement and analysis.

Signal analyzers have unique signal processing techniques that spectrum analyzers do not have. In addition to the superheterodyne method, this method uses a high-speed A/D converter to convert the signal to a digital signal, load the data into memory, and perform a high-speed Fourier transform.

This method enables analysis of recent digital modulation waveforms such as LTE and 5G, which have complex time response components and cannot be analyzed with conventional spectrum analyzers due to time response limitations.

2. Signal Analyzer Price

Signal analyzers tend to be priced in a wide range because the internal memory and digital processing power required for analysis vary greatly depending on the supported functions and frequency range. 

What Is a Thermal Relay?

A Thermal Relay is a component that outputs a contact when a current exceeding a set value flows into an electrical circuit. They are mainly used to prevent overloading of motors and wiring. By incorporating thermal relays into circuits, problems such as circuit burnout can be prevented.

Uses of Thermal Relays

Thermal relays are mostly used for motor protection. When a motor is subjected to a torque over its rating, a current more than the rating will flow. This phenomenon is called overcurrent.

When a motor is in an overcurrent state for an extended period, the internal windings heat up. This causes the internal varnish to melt or the windings to burn out. This is called motor burnout. When a current exceeding the rated value flows, the thermal relays shut off the power supply using a contact output to protect the motor.

Principle of Thermal Relays

In most cases, bimetals are used as circuit conductors inside thermal relays. Bimetal is a material that combines two types of metals with different coefficients of thermal expansion. When heat is generated by an electric current, it is biased and deformed due to the difference in thermal expansion coefficients.

The bimetal inside the thermal relays use this bias to drive the contact point and output the contact. Thermal relays are available with different current settings depending on the thickness of the bimetal and other factors.

When a motor starts, the current is more than twice the rated value. Since the bimetal heats up and deforms, there is a delay time until it warms up. Due to this delay time, they do not react to the high starting current of the motor.

The output contact of thermal relays are fixed by a spring, and once activated, in most cases the output continues to be output until the reset button is pressed. This prevents overloaded equipment from restarting.

How to Select Thermal Relays

Thermal relays are selected according to the current rating of the motor to be protected. There are two types of motor protection elements: instantaneous and time-limited.

The momentary element is a protective element that shuts off the motor power supply instantaneously to protect the upper circuit in the event of a motor malfunction. Power fuses and motor relays are used for high-voltage motors, while shock relays and breakers are mainly used for low-voltage motors.

A time-limiting element is a protective element that detects motor overload and shuts off the power supply to protect the motor. Overcurrent relays are used for high-voltage motors, and thermal relays are used for low-voltage motors.

For low-voltage motors, a breaker, drive unit, and thermal relays should be selected in conjunction with the above. The breaker should be at least twice the motor’s rated current to avoid tripping due to the starting current. The drive and thermal relays should be selected according to the motor’s rated current, referring to the manufacturer’s catalog.

Other Information on Thermal Relays

1. Thermal Relays Settings

Thermal relays are classified into two types: bimetal type and electronic type.

• Bimetal type
  In the bimetal type, the relay is operated by thermal expansion of the bimetal. In the case of the bimetal type, the current value can be set by ±20% by turning the setting knob. Further setting changes are structurally impossible, so the relay must be replaced. If the device to be protected is a motor, check the manufacturer’s catalog for thermal relays suitable for the motor capacity.
• Electronic Type
  The electronic type is used when the drive to be protected is an inverter. The electronic circuit reads the current value flowing in the circuit and operates when it deviates from the load characteristic curve. Most inverters on the market are equipped with this function as an inverter protection function. Electronic thermal relays are also used in motor control centers. The setting method for electronic thermal relays varies from manufacturer to manufacturer, but the lower current limit can be set more widely than that of the bimetal type. Check the instruction manual for the setting. Normally, the setting is done automatically by setting the rated current value. 

2. Thermal Relays Contacts

The thermal relays have two types of contacts: a normally open contact (a-contact) for monitoring and a normally closed contact (b-contact) for breaking the circuit.

• Bimetal Contacts
  In the case of the bimetal type, the number of which to use must be selected at the purchase stage. The current rating for the contacts is determined by the relay and is usually around 2A. Since there is a high risk of welding if they are used in the main circuit, they are used for control circuits.
• Electronic Contacts
  In many cases, electronic thermal relays can be set to use any number of contacts. However, electronic types may have transistor contacts instead of relay contacts. With transistor contacts, the electronic components will fail if an AC control power supply is used.

3. Return of Thermal Relays

When an overload condition persists and the thermal relays operate, the output contact of the thermal relays must be deactivated after the cause is removed. This procedure is called “recovery” or “resetting.”

There are two types of reset procedures: manual reset and automatic reset. The manual return type is simple, press the reset button after removing the cause of the overload. By pressing the reset button, the output contact is released.

The automatic reset type does not require pressing the reset button, but the thermal relay automatically resets itself. It is used in special applications where it is difficult for people to approach the thermal relays.

4. Thermal Relays Deterioration Factors

Although it varies from manufacturer to manufacturer, the recommended replacement period for thermal relays is approximately 10 years. However, since periodic replacement of thermal relays are costly, in most cases only periodic replacement of thermal relays for critical loads is required.

Since thermal relays are composed of bimetals and resins, which do not deteriorate easily, they rarely deteriorate naturally. The following four factors are known to cause forced deterioration. 

• Electrical Factors
  Insulation degradation occurs depending on the magnitude and frequency of drive voltage, frequency, and inrush current. This causes the thermal relays to fail. 
• Mechanical Factors
  Physical factors such as loosening of screws, shock, and vibration can cause deterioration such as metal fatigue. 
• Thermal Factors
  Thermal factors such as overvoltage, overcurrent, and self-heating cause thermal relays to warp, deform, or melt and break, resulting in failure.
• Environmental Factors
  Metal corrosion is caused by high temperature, high humidity, corrosive gases, oil mist, etc. Dust and foreign matter can also bite into the thermal relays, resulting in poor contact. By understanding the causes of deterioration and avoiding these factors, it is possible to extend the life of the product by the user.

5. Wiring of Thermal Relays

Thermal relays are often used as part of electromagnetic switches. In such cases, the primary side of the main circuit is usually connected with a copper bar for power supply in commercial products. The secondary side wiring should be designed to have an allowable current greater than the rated current of the thermal relays.

The allowable current for wiring varies depending on the type of wiring, but each type is defined by the internal wiring regulations. Wiring sold in Japan complies with the extension regulations.