月: 2023年7月

What Is a Thermal Cutoff?

Thermal cutoffs are components that detect abnormal heat generation in electronic equipment caused by internal failures or errors, and protect against overheating by melting themselves to cut off the current in the electronic circuit.

Thermal cutoffs generate almost no heat themselves, but rather they melt when the ambient temperature rises, thereby interrupting the current flow. When a thermal cutoff detects a temperature abnormality, it immediately interrupts the circuit current.

This can prevent smoke and fire from occurring in household equipment and automobiles. Once thermal cutoffs detect abnormal heat generation and shut down, they do not automatically resume conduction even if the ambient temperature decreases.

Applications of Thermal Cutoffs

Thermal cutoffs are used to prevent hazardous conditions when the object to be measured becomes hot due to abnormal heat generation, etc., because they do not automatically return to normal operation once they detect a blown thermal cutoff. Specific applications are as follows:

• Large Household Appliances
  Air conditioners, refrigerators, washing machines, fan heaters, hot-water washing toilet seats, gas water heaters, etc.
• Small Home Appliances
  Coffee makers, electric kettles, home bakeries, rice cookers, hot plates, electric stoves, irons, hair dryers, humidifiers, etc.
• Office Equipment
  Copy machines, printers, fax machines, etc.
• Automobiles
  Car air conditioners, seat heaters, engine cleaners, etc.

In the automotive field, thermal cutoffs are used to protect the surface of coils in transformers and motors that may become hot due to circuit malfunctions, and in resistors used to prevent inrush currents in power circuits.

However, it should be noted that once a thermal cutoff blows, it does not automatically recover, so the electronic equipment cannot be used again.

Principle of Thermal Cutoffs

There are two types of thermal cutoffs: fusible alloy-types using a fusible alloy as the thermosensing element and pellet types using a thermosensing element.

1. Fusible Alloy Type

When the thermal cutoff reaches the melting point of the low-melting-point alloy, the alloy changes from a solid to a liquid. The fusible alloy that has become liquid separates into two spheres, thus interrupting the fuse‘s conduction path.

2. Thermosensitive Pellet Type

When the ambient temperature of the fuse rises, the temperature-sensitive pellet melts and liquefies, forcing a distance between the contact electrode and the lead wire, thereby interrupting the fuse’s conduction path.

Most fusible alloy-type thermal cutoffs have a rated current from 0.5A to several A. Most temperature-sensitive pellet-type thermal cutoffs have a rated current from several A to 10A.

Other Information on Thermal Cutoffs

1. Nominal Operating Temperature

Nominal operating temperature is the temperature at which thermal cutoffs will blow when measured by the method defined in safety standards.

International IEC standards specify an error of plus or minus 0°C, plus or minus 10°C. In most cases, the nominal operating temperature is indicated on the body of the thermal cutoffs. 

2. Holding Temperature

The ambient temperature at which thermal cutoffs can withstand a minimum of 168 hours without melting while the rated current continues to flow through them. Thermal cutoffs should be selected based on the current and life expectancy of the equipment in which they will be used.

3. Operating Temperature Limit

The maximum temperature at which a thermal cutoff will not conduct again after it has blown. If a thermal cutoff continues to be used when the ambient temperature is above the operating temperature limit, the thermal cutoff may be destroyed.

4. Shape

There are two types of thermal cutoffs: axial and radial. Axial components have leads coming out from both ends of the component and are supplied with both ends of the leads taped. Radial components have leads coming out from one side of the component and are supplied with the leads coming out in one direction taped together.

What Are Wirewound Resistors?

Wirewound resistors are resistors with a structure in which resistors, which are electric heating wires, are wound around a porcelain material.

There are various types and characteristics of resistors, and they are used according to their applications and purposes.

Types of resistors:

• Chip resistors: Resistors mounted on the surface of a substrate.
• Carbon film resistors: Resistors with a carbon film formed on the surface of a porcelain material as a resistive element.
• Metal film resistors: Resistors with the same structure as carbon film resistors but using metal such as nichrome as a resistive element.
• Metal oxide film resistors: Resistors using metal oxide such as tin oxide as a resistive element.
• Metal-glass film resistors: Resistors using a mixture of metal and glass as a resistive element
• Wirewound Resistors: Resistors using a heating wire in a porcelain material.

Applications of Wirewound Resistors

Wirewound resistors are resistors consisting of an electric heating wire wound around a porcelain material, and have a low temperature coefficient and good heat resistance. They have a low temperature coefficient and good heat resistance. They are also used as resistors for current detection because they have relatively low current noise and resistance values.

The disadvantage of wirewound resistors is that they have an inductance component due to the structure of the resistor wire wound on a bobbin, and their high-frequency characteristics are not very good. The resistance value is adjusted by the wire type and number of turns, and resistors with higher resistance values are larger and more expensive.

Principle of Wirewound Resistors

Wirewound resistors have a structure in which electric heating wire is wound around them. They are characterized by their ability to obtain large power at low resistance values and are used in resistors for current detection. There are several types of wire-wound resistors, depending on the type of case.

1. cement resistors

Wirewound resistors and other types of resistors are placed in a ceramic case and sealed with cement. They have excellent insulation and heat resistance from the structure. The disadvantage is that high frequency characteristics are not good because of the inductance component as with wire-wound resistors.

2. Metal Clad Resistors

This type of resistor consists of wirewound resistors with metal cladding. Wirewound resistors are equipped with a metal cladding such as an aluminum case with heat dissipation fins to provide excellent resistance to environmental changes (heat resistance, physical properties, pressure resistance, and insulation).

3. Holo Resistors

This resistor is made by winding a resistance wire around a ceramic core and baking enamel over it to enhance heat resistance. Enameled resistors are suitable for handling large amounts of power due to their extremely high heat resistance. The disadvantage is that, like other resistors, it has an inductance component due to its wire-wound resistance, and its high-frequency characteristics are not good.

What Is a Crystal Filter?

Crystal filters are filters that use quartz crystals. Crystal filters are mainly used as band-pass filters to extract the required frequency components.

Crystal filters are effectively used to selectively extract frequencies because quartz crystals have high Q and steep passband characteristics.

Similar to crystal filters, SAW filters are sometimes used because they can extract the required frequency components.

Applications of Crystal Filters

Crystal filters can select only specific frequency components from a wide range of frequency components and attenuate unwanted components. For this reason, they are often used in equipment that requires highly accurate frequency selection. The most common application is in wireless communication equipment.

Wireless equipment uses a signal called a carrier wave. Carrier waves are the basic waves, such as radio waves, used to transmit and receive information. When creating a wireless signal, the information to be sent is superimposed on the carrier wave to create a communication signal. The carrier wave is then separated when it is received. In wireless equipment, it is necessary to separate the necessary frequencies from the unnecessary frequencies, and filters such as crystal filters are often used.

Principle of Crystal Filters

Crystal filters are filters that use the high Q of crystal units, where Q stands for Quality Factor and is called selectivity.

The larger the Q value, the narrower and sharper the bandwidth, and the smaller the Q value, the wider and gentler the bandwidth and frequency response.

The Q value can be calculated as follows and is expressed in terms of how much bandwidth characteristic it has in relation to the center frequency.
Q = ωo / (ω2 – ω1)
where ωo: center frequency, ω2, ω1: frequency of 1/√2 intensity relative to ωo.

A band-pass filter using LC, which is a common passive component, has a Q value of about 10^2. Crystal Filters have a high Q value of about 10^3 to 10^6, and Crystal Filters can be configured to have a high Q value. When a high Q filter is used as a band pass filter and the signal is passed through the filter, there is almost no output at frequencies other than the center frequency, making it possible to create a circuit that selectively obtains a specific frequency.

What Are Physical Batteries

Physical batteries are batteries that generate electrical energy without chemical reactions. They use light or heat to obtain electrical energy. Solar, thermal, and nuclear batteries are examples of physical batteries.

Batteries are broadly divided into physical and chemical. Chemical batteries convert chemical reactions into electrical energy. Chemical batteries include primary batteries, secondary batteries, and fuel cells. Primary batteries include alkaline, manganese, and lithium dry batteries, while secondary batteries are rechargeable batteries, such as lead-acid batteries and alkaline batteries.

Uses of Physical Batteries

Physical batteries output electrical energy through the physical transfer of electrification, like semiconductors, without the use of chemical processes. Solar cells are a typical example of physical batteries.

Photovoltaic power generation has been in the limelight in recent years as a means of solving environmental problems, and the production of solar cells for industrial and residential use is rapidly increasing under government subsidies. In general, the majority of solar cells are installed on roofs or on land, where they can receive sufficient solar radiation to maximize their power generation capacity.

Principle of Physical Batteries

Solar cells have been attracting attention as physical batteries in recent years. Solar cells are made of semiconductors, which absorb sunlight and convert it into electrical energy. Despite the name “battery,” they do not have a storage function. The semiconductor atoms that make up a solar cell generate electrons and holes when they are exposed to sunlight.

A solar cell is composed of a P-type semiconductor and an N-type semiconductor superimposed on each other, with holes collecting in the P-type semiconductor and electrons in the N-type semiconductor. This generates a voltage between the holes and electrons, similar to that of a dry cell. Electricity can be extracted by connecting wires to the P-type semiconductor, which serves as the positive electrode, and the N-type semiconductor, which serves as the negative electrode.

There are several types of solar cells, which can be broadly classified into two types: silicon-based and compound-based. Each has different performance and characteristics, and the two types widely used for industrial and residential applications are silicon-based monocrystalline and polycrystalline. Compound monocrystalline solar cells have high power generation efficiency but are expensive, so they are often used for space applications such as satellites.

What Is a High-Side Driver?

A high-side driver is a circuit configuration used on electronic circuits to drive a switch element between a power supply and a load.

The switch element to be driven is called a high-side switch, and the high-side switch is controlled to turn the power supply on and off and to supply or disconnect current to the load. In contrast, a driver that drives the switch element placed between the load and ground is called a low-side driver.

To supply current to various loads, high-side drivers and low-side drivers have unique characteristics in their respective circuits.

Uses of High-Side Drivers

High-side drivers are widely used in electronic circuits. Typically, they are used in inverters, power on/off circuits, LED drive drivers, and to drive inductance loads such as motors and solenoids.

High-side drivers are often used to supply large currents to loads, and must be designed with inrush current countermeasures and reverse current prevention circuits in mind. Since a switch element is inserted between the load and the power supply, it is possible to design the driver with consideration for operation in the event of a ground short circuit or other failure.

Types of High-Side Drivers

High Side Drivers

High-side drivers monitor the current flowing through the switch because the switch element to be driven is placed between the power supply and the load. A ground short can be detected, and the overcurrent caused by the short can be stopped by turning off the switch.

Low-Side Drivers

Low-side drivers can easily use N-channel MOSFETs because the voltage between the gate and source is ground referenced. Even if the voltage applied to the load is high, the voltage on the driver side does not depend on the voltage on the load side, and a low supply voltage is sufficient. The selection of elements can be aggressive even with low withstand voltage elements, and the configuration can be advantageous in terms of size and cost.

The disadvantage of high-side drivers and low-side drivers is that they cannot match the advantages of each other. High-side driver configurations are often larger and more expensive than low-side drivers. Low-side drivers are not as protected against short circuits, which is possible with high-side drivers.

What Is a Torque Limiter?

Torque limiters are devices that protect equipment from overload and contribute to improved productivity.

They are mainly used in multilevel parking lot turntables, pallet cart conveyors, and various types of training machines.

Applications of Torque Limiters

Torque limiters are used for three main purposes: accumulation, breaking, and dragging.

Accumulation stops the driven side in position using a stopper action. An example of a practical application is a conveyor that utilizes the stopper action.

Braking stops continuously driven equipment by braking action. An example of a practical application is a turntable in a multilevel parking garage that utilizes braking.

Dragging applies a steady load to a device using a slipping action. An example of a practical application is a training machine that utilizes the slipping action.

Principle of Torque Limiters

Torque limiters are devices that maintain a constant torque. The basic configuration of the device is generally made up of seven mechanical parts: hub, plain bearing, flange, plate, disc spring, washer, and adjusting nut.

The device transmits drive to an external drive up to a specified torque, but slips and stops transmitting drive when the specified torque is exceeded. Torque adjustment is determined by loosening or tightening an adjusting bolt attached to the far end of the device. The torque setting range varies from 10 to 30 Nm for small products and from 100 to 600 Nm for large products.

Other Information on Torque Limiters

Features of Torque Limiters

1. Compact and Lightweight
The device consists of only a few mechanical parts, making it compact and lightweight.

2. Built to Last
The use of chemical fiber for the plate extends the life of the device.

3. Low-Cost and Lightweight
The use of aluminum for the flange enables low-cost and lightweight equipment.

4. Easy Torque Adjustment
Torque adjustment is easy by simply turning the adjustment bolt according to the torque scale.

What Is a Dust Sensor?

Dust sensors, as the name suggests, are elements that detect dust, and are used to detect particles floating in space in general home environments and particle-controlled clean rooms. Dust sensors are widely known for general household use, such as in air purifiers and air conditioners with built-in dust sensors.

A particle counter is similar to a dust sensor. These detectors detect suspended particles based on the light scattering principle. It can detect cigarette smoke, house dust that causes allergies, etc.

Applications of Dust Sensors

Dust sensors optically detect airborne particles such as house dust and tobacco smoke. They are used in air purifiers, air conditioners, ventilation fans, environmental monitors, and other sensors that use light to detect various types of dust, cigarette smoke, house dust, and other particles.

Duct sensors are often used in air purifiers and air conditioners that detect particles suspended in the air and monitor their condition, or change their operation according to the state of particles in the air.

Principle of Dust Sensors

Dust Sensors consist of a light-emitting diode that emits light and a photodiode that receives light reflected from dust. In addition, a lens is used to collect the light efficiently, and a heater is used to generate a weak updraft of air inside the sensor, which draws in dust and smoke from the air intake. Dust and smoke are then discharged from the exhaust port.

The light-emitting diode (e.g., infrared) emits light in pulses in response to an external input signal. A photodiode, which is the light-receiving element, receives the incident light from the light-emitting diode and outputs a pulse current in response to the amount of incident light.

Aspheric lenses are installed on all surfaces of the light-emitting and light-receiving elements to narrow directivity. The area where the optical axes of the emitting and receiving elements intersect is the area where dust, smoke, etc. are detected. To prevent unnecessary light from entering the light-receiving element as stray light, a slit, or the like, is added to the sensor case to reduce stray light.

Cigarette smoke and house dust can be distinguished by looking at the temporal transition of the output voltage. If the output voltage is detected continuously, it can be identified as cigarette smoke, and if the output voltage is detected intermittently, it can be identified as particles such as house dust.

What Is an Inlet?

Inlets are connectors used to connect AC power cables to electronic equipment powered by AC power.

They are called because they serve as the AC power inlet for electronic equipment. The advantage of using an inlet is that the AC power cable can be disconnected from the electronic equipment, allowing for AC power cable replacement and improved portability of the electronic equipment.

If inlets are not used, the AC power cable is pulled directly from the electronics. Note that two types of inlet mounting methods exist: screw-fastening and snap-in types.

Uses of Inlets

Inlets are used as connectors for AC power supply cables and are attached to the panel of an electronic device. AC power can be supplied to an electronic device by connecting the inlet plug of the AC power cable to the inlet of the electronic device and the plug of the AC power cable to a power outlet.

Inlets Principle

Inlets are 2- or 3-terminal female connectors into which male AC power cable inlet plugs are inserted. 2-terminal inlets consist of an N-terminal and an L-terminal, while 3-terminal inlets consist of an N-terminal, an L-terminal, and a ground terminal.

Types of Inlets

1. Multi-Functional Inlets

Multifunctional inlets that incorporate fuse holders, switches, and noise suppression filters also exist. The advantages of multifunctional inlets are that they enable the downsizing of electronic equipment, reduction of the number of components, and reduction of assembly man-hours.

However, the cost of multifunctional inlets is higher than that of single-functional inlets. 

2. Inlets With Fuse Holders

Inlets with fuse holders are inlets that incorporate holders to which tube fuse-type fuses can be attached. Fuses can be replaced without disassembling the electronic equipment.

Since many components do not have fuses installed and wiring between fuse terminals and power supply terminals, fuse installation and wiring between terminals should be performed when the electronic equipment is assembled. 

3. Inlets With Switches

Inlets with a locking switch. The switch is wired to the terminals of the Inlets, so no work is required during the assembly of the electronic equipment.

The 1-pole switch turns the L terminal and the device ON/OFF, and the N terminal and the device are always connected. 2-pole switches turn both the L terminal and the device ON/OFF and the N terminal and the device ON/OFF. A switch with a lamp is also available, and the ON/OFF of the switch is interlocked with the ON/OFF of the lamp.

4. Inlets With Noise Suppression Filters

Inlets with built-in noise suppression filters for AC power lines are effective in reducing noise entering electronic equipment from AC power lines and reducing noise emitted from equipment to AC power lines.

Inlets with built-in noise suppression filters have a greater depth than single-function inlets, so care must be taken to avoid interference with other components in the electronic equipment.

How to Select Inlets

1. Rated Voltage, Rated Current, and Rated Temperature

As with other connectors, select inlets rated for the voltage, current, and temperature environment in which the electronic equipment operates. Selecting inlets with higher ratings than necessary will result in larger inlet sizes and thicker AC power cables to be used.

2. Presence of Ground Terminal

There are two types of inlets: 2-pole and 3-pole. If the inlets do not require a ground terminal, select 2-pole. Conversely, if the inlets require a ground terminal, select 3-pole.

Other Information on Inlets

Shape of Inlets

Inlets are defined by the International Electrotechnical Commission (IEC), and there are a total of 11 types of inlet shapes. The two main types are spectacle-shaped and hexagonal.

Hexagonal inlets have a larger external size but a higher-rated current. Therefore, it is important to select the inlet plug shape of the AC power cable to be used according to the inlet shape.

What Is a Floor Lift?

A floor lift is a labor-saving piece of equipment that can be raised and lowered to eliminate steps and improve work efficiency.

It is installed externally or embedded in the floor area. It can automatically raise and lower objects using motors, hydraulic pressure, or other power sources. The table width varies depending on the product, so use a Floor Lift with the appropriate width for your application. Since heavy objects such as automobiles are lifted, robust materials with excellent load capacity are used for the components. Safety devices are also installed in case of emergency.

Uses of Floor Lifts

Floor lifts are used in a variety of fields, including homes, nursing care facilities, factories, and maintenance facilities. In homes and nursing/rehabilitation facilities, floor lifts provide barrier-free access to eliminate differences in level. They are installed on a portion of the floor to eliminate steps by lifting and lowering, or to reduce the burden on users by assisting the movement of wheelchairs and other vehicles.

In factories and maintenance facilities, they are used for maintenance work on large equipment and vehicles. Pit work at vehicle maintenance shops includes a variety of tasks ranging from relatively quick maintenance such as oil changes and transmission removal and installation to heavy-duty maintenance. Floor Lifts are used to lift vehicles to a comfortable working height for efficient work.

Principle of Floor Lifts

A floor lift consists of an arm that raises and lowers the vehicle, a floor section that loads the object to be moved, a power section that moves the arm, and a safety device. By using a pneumatic or hydraulic drive system for power, even heavy loads can be raised and lowered.