月: 2023年2月

What Is a Geared Motor?

A geared motor is a device that combines gears and a motor. By combining gears and motors, the number of revolutions and torque can be designed as desired.

Compared to belt pulleys, geared motor produce less noise due to friction and are easier to maintain. The appropriate gear is selected by selecting the gear ratio based on the motor’s rotation speed and torque. The size of the gearhead must also be checked, as it requires space for the gearhead.

Mounting methods include flange-mounting and tap-mounting types.

Uses of Geared Motors

Geared motors provide high torque at low RPMs due to their gears. They are often used especially in large machinery such as food processing machines, multilevel parking garages, semiconductor manufacturing equipment, and woodworking machinery.

Familiar examples are also used in electric shutters and car washes. Taking advantage of their low RPM and high torque characteristics, they are also used in industrial robots.

Geared motors come in many sizes, from ultra-small to large. In addition, geared motors are available in a wide range of products, including those with electromagnetic brakes and those using stepping motors.

Principle of Geared Motors

Geared motors consist of a motor and a reduction gear.

While the motor rotates at high speed, the reduction gear adjusts the speed of rotation by combining gears. Geared motors have a high torque at a low rpm due to the reduction gear.

Three-phase induction motors are often used in industrial applications. Since the rated speed of induction motors is determined by the frequency and number of poles, the speed and torque are selected by adjusting the gear ratio.

The gear ratio is the rotation ratio of the motor rotation shaft to the reduction gear output rotation shaft. The higher the gear ratio, equates to the higher the torque.

The parallel or perpendicular shaft is selected according to the position of the gear and motor. A clutch brake type may also be used when the motor is frequently run and stopped.

How to Use Geared Motors

There are many ways to use geared motors, of which the most typical are deceleration, high load, and high precision.

1. Reduction of Speed

The rotational speed of a three-phase induction motor, for example, is determined by the number of poles and frequency. Therefore, to use induction motors at the required rotational speed, they are decelerated by a decelerator.

Since geared motors with various reduction ratios are sold by various companies, select a model that matches the required rotational speed.

2. High Load

The output torque increases in proportion to the reduction ratio due to deceleration, and the allowable moment of inertia increases in proportion to the square of the reduction ratio. This makes it possible to rotate large objects at the cost of reduced speed.

3. High Accuracy

When used for positioning operation, the stopping angle accuracy of the motor is improved.

For example, with a reduction ratio of 2, if the error of the motor output shaft is 1.0°, the error of the reducer output shaft is 0.5°, resulting in better accuracy. However, many reduction gears have play, called backlash, and care must be taken when using them for high-precision positioning.

Other Information on Geared Motors

Reduction Gears for Geared Motors

There are various types of reduction gears used in geared motors, which are selected according to the application. Typical examples include spur gear reducers, bevel gear reducers, hypoid reducers, worm reducers, planetary gear reducers, and wave gear reducers.

1. Spur Gear Reducer
Spur gear reducers are the most common type of gear reducer and use a combination of spur gears to reduce speed. They are also available in multi-stage types and can be manufactured with large reduction ratios, but they have a large backlash.

2. Bevel Gear Reduction Gears and Worm Reduction Gears
In bevel gear reducers and worm reducers, the input and output shafts are orthogonal. Worm reduction gears have a self-locking function and are often used in elevators.

3. Hypoid Reduction Gears
Hypoid reduction gears use spiral bevel gears and feature a large reduction ratio and smooth power transmission.

4. Planetary Gear Reducer
Planetary gear reducers are reducers that use planetary gears, and the input and output shafts are concentric. Planetary gear reducers are often used in stepping motors.

5. Wave Gear Reducer
Wave reduction gears are also called “harmonic reduction gears” after the company named Harmonic Drive Systems, which developed them. They are often used in robot joints as reduction gears with no backlash.

There are also ball reduction gears, cyclo reduction gears, etc. Since the output characteristics vary depending on the reduction gear, it is important to know the characteristics of the reduction gear when selecting geared motors.

What Is a PWM?

A PWM stands for “pulse width modulation” and is a technology for generating pulse waves of various widths. Pulse waves are digital signals, but by combining various pulse waves, they can be converted into various pseudo-analog signals, including sine waves.

A PWM is a technology that modulates the pulse width with a fixed period. There is also a PFM technology that modulates the frequency with a constant pulse width, but both are used for switching between energized and de-energized.

Uses of PWMs

PWMs are used to control the voltage of power supplies and to control the energizing and de-energizing cycles of semiconductors. In particular, it is often used to control DC motors efficiently. By controlling the time of voltage application to the motor, it is possible to control the running voltage.

In addition, when generating modulated AC current in an inverter circuit, PWMs can be used to generate pulse voltages with various widths, which can then be synthesized to perform DC-AC conversion. PWMs are used not only in inverter circuits but also in controlling switching power supplies and dimming LEDs without affecting the light color.

Principle of PWMs

PWM circuits, which perform pulse width modulation, use transistors to generate pulse waves of various widths by repeatedly switching the circuit on and off.

PWMs modulate the pulse width over a fixed period, so the duty cycle is varied. The duty cycle is the pulse width divided by the period, expressed in “% (percentage).” In voltage control, the running voltage is the product of the pulse voltage and duty cycle, and a duty cycle of 100% is the same as when a DC power supply is used.

When voltage control is performed using PWMs, the power supply is turned off for a period, which makes it more power efficient than using a DC power supply that works steadily. In addition, in digital circuits such as microcontrollers, pseudo-analog signals can be generated simply by synthesizing pulse waves, making it possible to construct analog conversion circuits composed entirely of digital circuits without the use of D/A converters or other devices.

Other Information on PWMs

1. Control

When dynamically controlling a load with an electronic circuit, there are two methods: one is to control the load with a constant voltage and the other is to control the load with a constant current, and the other is to control the load with PWMs.

Recently, more energy-efficient methods have become the trend due to environmental and energy issues. The reasons for the low efficiency of linear methods, such as constant voltage control and constant current control, are as follows.

• A margin of several V is required for stabilization.
• When voltage or current is reduced, the reduced component is consumed in the circuit and becomes a loss.

For example, if a regulated power supply with a maximum voltage of 10 V and current capacity of 2 A is used at 5 V 2 A, the power loss consumed in the power supply circuit is (12 V – 5 V) x 2 A = 14 W when the input voltage of the power supply is 12 V. The power consumed in the load is 5 V x 2 A = 10 W.

The power consumed by the load is 5V x 2A = 10W. 1.4 times the power consumed by the load is consumed as a loss in the circuit. This is not only wasteful power consumption but also increases the cost, size, and weight of the circuit due to the large number of components used.

On the other hand, PWM control does not change the output voltage but varies the pulse width according to the output. For example, with PWMs at 10 V and a duty ratio of 50%, the apparent drive voltage is 5 V, which means that there is no theoretical loss and the actual efficiency is very high.

2. Duty Ratio

In PWM control, the term duty ratio is often used. In a PWM waveform with a duty ratio of 50%, the H and L pulses are the same width.

Changing the duty ratio changes the apparent voltage. For example, when the duty ratio is changed from 0% to 25% to 50% to 75% to 100% with 10V PWMs, the apparent voltage to the load changes from 0V to 2.5V to 5V to 7.5V to 10V.

Although a microcontroller requires a D/A converter to output an analog signal, it is possible to create a pseudo-analog signal by using PWMs, which have a moderate switching frequency and a programmable duty ratio. In this case, it is possible to generate an appropriate analog signal up to the digital signal level at the I/O pins.

In this case, an appropriate LPF must be inserted in the I/O pin to remove the PWM switching frequency component and its harmonic components.

3. Noise of PWM Control

As mentioned above, PWM control is often used to control motor operation and to increase the efficiency of inverters. This generates noise at various switching frequencies, which range from 30 to 40 Hz.

This frequency is approximately 30 to 40 MHz, which not only causes noise problems for the surrounding people and environment but also affects AM radios and sensors that use low-frequency bands. Therefore, some sort of noise countermeasure is often required. Specific measures include, in the case of inverter equipment, covering the equipment with a housing, shortening the power cable, and inserting noise filters such as ferrites or LC chokes.

In some cases, PWM control allows the user to change this switching frequency, so it is another option to try. Lowering the switching carrier frequency reduces the overall switching noise itself, but generally increases the noise of the motor.

There are examples of products that reduce motor-specific generated noise by employing a modulation method that actively distributes the switching carrier frequency from low to high frequencies.

What Is a Laser Scanner?

A laser scanner is a measurement device that acquires positional information of an object in three dimensions. A laser beam emitted from the scanner is directed at the object, and the reflected light is used to measure positional information, such as distance and angle.

Non-contact, non-prismatic measurement is possible, so measurements can be taken safely. It can also acquire a large amount of 3D information as point cloud data.

There are four main types of laser scanners:

• Ground-based 3D lasers
• UAV lasers
• Aerial lasers
• MMS (Mobile Mapping System)

Uses of Laser Scanners

The main applications are surveying in facility design, plant maintenance, construction sites, etc. They are also useful for documenting existing conditions and creating CAD models.

Other uses include measuring topography, surveying displacement in tunnels and existing structures for civil engineering and maintenance and repair, and accurately recording accident and crime scenes in criminal investigations.

Furthermore, they are also used to measure surface profiles projected in 3D projection mapping and can be used in a variety of other situations.

Principle of Laser Scanners

Laser scanners measure positional information by irradiating a laser beam onto an object and detecting the reflected light. Position information can be measured without directly touching the object.

There are two main measurement methods.

1. Time-Of-Flight Method

A laser beam is irradiated onto an object, and the time it takes for the reflected laser beam to return and the laser irradiation angle are measured. The distance is calculated from the measurement time, and the coordinate position is calculated using the measurement angle and XYZ coordinates.

This enables the acquisition of 3D coordinate data, as well as a great deal of information for each point, such as RGB color coordinates, reflection intensity, reflection rate, and even angle information.

The time-of-flight method requires a longer measurement time to obtain more information, but it can provide highly accurate measurements.

2. Phase Shift Method

Multiple modulated laser beams are irradiated onto an object, and the distance to the object is determined by measuring the phase difference between the reflected light from the object and the emitted light.

Compared to the time-of-flight method, the phase-shift method is more prone to noise in the measurement and has a shorter measurement distance. However, the measurement time is much shorter.

Summary

The time-of-flight method is suitable for high-precision measurement, and the phase-shift method is suitable for measurement time.

The data acquired by the laser scanners are read by dedicated software.

Coordinate data is expressed as dots on the screen, and based on this information, the measured local conditions are reproduced on the PC. The data within the detection range is comprehensively acquired, so the situation can be reproduced.

Other Information on Laser Scanners

Cars and Laser Scanners

Modern automobiles are equipped with ADAS (advanced driver assistance systems), which supports safe driving. 

In the last few years, advances in automated driving technology have led to the addition of a new sensor based on laser scanners called LIDAR (light detection and ranging).

LIDAR is a sensor that can detect objects at a close range with higher accuracy than conventional radar. LIDAR is used in automated driving because it is necessary to measure the distance to an object with higher precision.

However, laser scanners cannot replace millimeter-wave radar and other sensors. Each has its advantages and disadvantages, and they are used in a complementary manner.

Laser scanners are excellent at detecting objects at short distances with high accuracy, but their detection performance is easily affected by bad weather conditions such as rain and fog.

Millimeter wave radar is less susceptible to weather conditions and has a better detection performance for objects at long distances than laser scanners. However, the detection performance of millimeter-wave radar is inferior to that of laser scanners for objects at close range, and for objects with poor radio wave reflectivity.

What Is a Level Switch?

A level switch is a type of sensor used to detect the remaining amount of a substance, such as liquid or powder.

It is indispensable for inventory control and maintenance operation of product tanks. There are many types, from simple to highly precise.

Uses of Level Switches

Level switches are primarily used in material storage facilities. These include tanks for storing liquids such as tap water and chemicals, and service hoppers for dropping powder materials.

Tanks also come in a variety of shapes, sizes, and installation methods, so the appropriate level switches are used depending on the orientation and situation in which it is installed. The purpose of installation can be classified into cases where the switch is installed simply to detect and report the remaining amount in the tank, and cases where the switch provides some kind of feedback control to other equipment when a certain threshold value is crossed.

Principle of Level Switches

Level switches can be broadly classified into two types: the “float type” that detects liquids, and the “sound type” that detects powders and other substances.

1. Float Type

Float-type level switches, which are often used to detect liquids, are level switches with a float attached and are mechanically controlled. When the float is not in contact with the liquid, the float is tilted and the internal circuit on the opposite side of the float is disconnected. On the other hand, when the float is pushed up by the liquid, the circuit on the opposite side makes contact and conducts the circuit, thus detecting a transition. However, the float type can only detect liquid.

2. Sonic Type

Sound level switches are used to detect powders. A sound level that constantly vibrates at a certain frequency is prepared, and when a powder or other object comes into contact with the level switches, a different frequency from that in the air is detected. The change in frequency is used to determine the position of the powder.

How to select Level Switches

The level switches to be selected depend on whether the substance to be detected is a liquid or a solid, such as powder. For simple applications, such as detecting the remaining amount of liquid, a float switch would be suitable. For chemicals, it is important to check for chemical resistance.

For solids, sound level switches are suitable, but depending on the particle size or size, there may be problems such as getting caught at the sound level. There are also level switches that use other principles, such as electrode-type switches, so it is a good idea to consult with the manufacturer.

Other Information on Level Switches

1. Electrode Type Level Switches

Electrode-type level switches consist of an amplifier, which is a power supply unit that applies a very low voltage between the electrodes, and a pole-holding device. The amplifier contacts often have hysteresis, shorting the contacts from the time the high electrode touches the surface of the liquid until the low electrode breaks the level.

The holding fixture is made of resin or other insulating material to insulate the electrodes from the surrounding fittings. The electrodes generally consist of three electrodes: a common electrode, a high-level electrode, and a low-level electrode. Two electrodes may be used for alarm purposes.

Float-type level switches cannot be used in tanks with agitators, whereas electrode-type switches can be used stably. However, they cannot be used with nonconductive liquids (e.g., oil).

Also, depending on the type of liquid, the electrode may dissolve due to corrosion, etc. Therefore, the electrode material must be carefully selected. In general, SUS304 or SUS316L is often used for the detection of less corrosive liquids. For highly corrosive liquids, Hastelloy or titanium are used, but they are more expensive.

2. Capacitive Level Switches

Capacitive level switches are level switches that can be used with powders and liquids. In principle, a grounded electrode and an electrode for detection are insulated and arranged, and the switch operates by detecting changes in capacitance between the electrodes when they come in contact with liquid. Since detection is based on capacitance, the level detection of insulating materials is also possible.

The shape is a single cylinder, which is attached to the side of a chemical tank or hopper. The disadvantage is that since it detects by contacting the object to be measured, there is a risk of false detection due to corrosion or sticking.

What Is a Passive Probe?

A passive probe is an electrical connection between the signal at a measurement point and the input terminal of an oscilloscope.

In the case of waveform observation with an oscilloscope, it is a device that transmits the signal to be measured from the measurement point to the oscilloscope.

There are two types of oscilloscope probes: active probes with built-in signal amplification circuitry and passive probes consisting only of passive components, but this paper will limit its discussion to the latter.

Uses of Passive Probes

A passive probe is used to detect the signal at a measurement point when observing a signal waveform with an oscilloscope.

The voltage at the applied point is transmitted to the oscilloscope. When observing current waveforms directly, current probes must be used.

Principle of Passive Probes

The use of a passive probe does not guarantee accurate waveform observation on an oscilloscope. Careful handling of the probe is required for accurate measurement.

1. Influence of the Passive Probe on the Circuit Under Test

When an oscilloscope is combined with a passive probe for waveform observation, the circuit under test is considered having the combined impedance of the oscilloscope’s input impedance and the probe’s impedance connected to it. That is, the probe has a built-in resistor Rp and a capacitor Cp for adjustment in parallel with it, and the cable of the probe has a stray capacitance Cs.

Since the input terminal of the oscilloscope consists of a parallel circuit of an input resistor Ri (1MΩ) and an input capacitor Ci, it is important to consider this combined impedance.

2. How to Adjust Cp

To obtain a constant attenuation rate regardless of frequency, Cp must be adjusted to satisfy the following equation.

　　　Cp = (Cs + Ci) × Ri / Rp

The adjustment capacitor Cp is a semi-fixed type, so it should be set to the optimum value in combination with the oscilloscope itself. The oscilloscope has a square wave output terminal for setting the optimum value of the adjustment capacitor.

Connect the tip of the probe to this terminal and change the value of Cp so that a square wave is displayed on the oscilloscope display.

Other Information About Passive Probes

1. How to Use Passive Probes

A passive probe is used for measurement with an oscilloscope, and is selected from three types of attenuation ratios 1:1, 1:10, and 1:100 by the built-in resistor Rp, based on the characteristics of the circuit under test.

1:1 Probe
A probe without built-in resistor Rp and capacitor Cp for adjustment. Since the signal is applied directly to the oscilloscope’s input terminal, the oscilloscope’s input impedance of 1MΩ and input capacitance Ci are connected to the circuit under test.

Care must be taken if the circuit under test has a high impedance, as this will affect the measurement circuit. On the other hand, when dealing with small signals, the input sensitivity of the oscilloscope can be used as it is, which is more advantageous in terms of signal level than other types that pass through Rp.

10:1 Probe
This is a general probe that is commonly used, with a built-in resistor Rp of 9MΩ. The input impedance is 10 MΩ when combined with an oscilloscope, making it easy to use with minimal influence on the circuit under test.

100:1 Probe
With a built-in resistor Rp99MΩ and a capacitor Cp for adjustment, this probe is mainly used when the signal voltage exceeds 100V because the attenuation factor is 1/100. It is also characterized by its extremely high input impedance of 100MΩ, which has particularly little effect on the circuit under test.

Connection Points for Ground Leads
Particular attention should be paid to the connection of ground leads and how to handle them when using Passive Probe. When observing multiple points simultaneously on a multi-channel oscilloscope, it is fundamental that the ground leads of each channel probe be connected to a single common point (preferably a single ground point).

Connecting to different ground lines will adversely affect the measurement of small signals due to ground loops.

Length of Ground Leads
Longer ground leads are advantageous in terms of connection to the measurement point, but when observing high-frequency signals, faulty phenomena such as ringing and large fluctuations in signal amplitude can occur. This is due to the resonance between the inductive inductance component of the ground lead and the input terminal capacitance of the probe, resulting in an extremely large amplitude near the resonance frequency.

Therefore, when observing high-frequency signals with a frequency of 10 MHz or higher, consider using a ground spring or the like in place of the ground lead.

2. Frequency Characteristics of Probes

The main measurement performance is determined by the frequency bandwidth and rise time of the measurement system that combines the oscilloscope and the probe. Therefore, the frequency bandwidth and rise time specifications are published for each oscilloscope main unit and probe combined with it.

3. Cable Flotation Capacitance

A factor that greatly affects the frequency response of a probe is the cable’s floating capacitance. The higher the frequency, the smaller the capacitive reactance due to the floating capacitance, which in turn increases the load on the circuit under test.

As a result, the frequency bandwidth of the probe itself is narrowed, the rise time is slowed down, and other adverse effects occur. The stray capacitance of a probe also depends on the length of the cable, and the longer the cable, the larger the stray capacitance tends to be, so it is advantageous to keep the probe length as short as possible in terms of frequency response.

What Is a Varactor Diode?

A varactor diode is a diode whose capacitance can be varied by applying a reverse voltage.

They are also called variable capacitance diodes or varicaps. Generally, when a reverse voltage is applied to the PN junction of a diode, the depletion layer, which is the area without carriers such as electrons and holes, behaves like a capacitor.

A varactor diode actively utilizes the property that the capacitance, which acts as a capacitor, varies depending on the magnitude of the applied voltage.

Uses of Varactor Diodes

Varactor diodes are used in electronic components, such as electronic tuning circuits and voltage controlled oscillators (VCOs). Electronic tuning circuits and voltage controlled oscillators (VCOs) are used in devices that receive radio waves, such as radios, televisions, telecommunications equipment, and mobile communication devices, such as smartphones.

In order for those devices to receive signals at specific frequencies, the capacitance of the capacitors in the receiver and the impedance value of the coil must be adjusted. For this purpose, varactor diodes are used, whose capacitance can be controlled by voltage.

Principle of Varactor Diodes

The principle of varactor diode is to utilize as capacitance the carrier-free depletion layer that is created when a reverse voltage is applied to the PN junction of the diode. Also, to actively use the characteristic that the value of the capacitance depends on the reverse voltage value. In an ordinary diode, forward current flows when a bias voltage is applied in the forward direction, and no current flows when a bias voltage is applied in the reverse direction.

When the voltage is applied in the opposite direction, holes move from the P-type semiconductor part to the electrode and electrons move from the N-type semiconductor part to the electrode, forming a depletion layer with no carriers in the PN junction part. Since there is no charge in the depletion layer and charge is generated on both sides of the depletion layer, the diode behaves like a capacitor.

If the absolute value of the applied voltage in the reverse direction is large, the thickness of the depletion layer increases by that amount, resulting in a smaller equivalent capacitance. A varactor diode is a diode whose capacitance changes by varying the value of the applied reverse voltage. This capacitance change characteristic is effectively utilized.

Other Information on Varactor Diodes

1. LC Resonance Circuit Using Varactor Diodes

Since the capacitance value of a varactor diode can be varied by the bias applied voltage, it is possible to form an LC resonance circuit with an inductor and adjust its resonance frequency.

Using an LC resonant circuit that can be varied by the voltage value, a voltage-controlled oscillator (VCO), for example, incorporates a resonant circuit in a Colpitts oscillator.

A voltage-controlled oscillator (VCO) is a part of the PLL (Phased Lock Loop), which is a frequency adjustment circuit for mobile communications. It is a very important circuit for cellular communication applications between base stations and mobile terminals. As a tuning circuit, the LC resonant circuit is also used in FM modulation applications, such as radio.

2. Etymology and Breakdown Voltage of Varactor and Varicap

The word “varactor” in varactor diode stands for “variable reactor,” meaning a variable reactance, and in the case of varactor diodes, it specifically refers to a capacitive variable reactance. Varicap, on the other hand, is an abbreviation for “variable capacitor” and literally means variable capacitance.

While both varactor and varicap are abbreviations for variable capacitance, it should be noted that the diode bias on the reverse side, where capacitance can be varied, also has a breakdown voltage (breakdown voltage). Check the electrical specifications of the varactor diode you plan to use carefully, and use a voltage within the usable range of the reverse side.

The breakdown voltage (breakdown voltage) is also called the Zener voltage, and diodes that actively use this region are also called Zener diodes. Zener diodes are often used in protection circuits to prevent overvoltages from being applied to the circuitry of the device, or in circuits for constant voltage generation.

What Is a GPS Module?

A GPS module is a device that receives GPS signals transmitted from a large number of satellites in space and determines location information.

GPS is an acronym for “global positioning system,” a system that can provide precise location information for the entire world. If accurate location information can be obtained from a GPS module, it is possible to calculate the speed and direction in which you are currently moving, as well as the distance to your destination.

GPS is a satellite positioning system operated in the United States, but Japan has its own satellite positioning system called MICHIBIKI, which can correct GPS information.

Uses of GPS Modules

GPS modules are used for positioning applications for devices that require motion, location information, travel speed, direction, etc.

Specific uses of GPS modules include the following:

• Position observation for use with map applications in smartphones and smartwatches
• Calculation of vehicle position, speed, direction, and distance to destination in car navigation systems

Depending on the product specifications of the GPS module, it is important to select a GPS module taking into consideration how much the position accuracy, calculation time, and degree of error in position information affect the product.

If there are obstructions to the GPS signal, such as being underground or buildings, the signal may not be received accurately. Some high-precision GPS modules are capable of receiving signals by processing signals made smaller by shielding.

Principle of GPS Modules

The principle of a GPS module is that it has a signal processing algorithm that receives GPS signals from satellites, processes and analyzes the signals, and calculates the module’s current position. The GPS signal to calculate accurate position information is processed by detecting and amplifying the weak signal and performing RF processing and baseband processing.

Each product has its own algorithm for processing GPS signals in order to improve position detection accuracy and reduce current consumption. GPS signals emitted from satellites are generally transmitted on two different frequencies. The signal contains the time of day when the signal is transmitted and the exact location of the satellite at that time.

The GPS signal is received by the receiver of the GPS module, which receives signals from four or more satellites. The GPS signals allow the distance from the satellites to be calculated, and if the distance from the three satellites is known, the current position on the earth can be calculated.

The fourth and subsequent satellites are used to adjust for time errors and help calculate more precise location information.

Other Information About the GPS Module

1. Frequencies Handled by the GPS Module

GPS modules usually operate in the L1 band (1575.42 MHz) and the L2 band (1227.6 MHz), and sometimes in the L5 band (1176.45 MHz).

The L1 band contains both a civilian identification code called the C/A code and a military code called the P code, with the C/A code usually used.

2. Positional Accuracy of GPS

Various factors affect the accuracy of a GPS module’s measurements, but the main sources of error are:

Ionosphere
A layer in the atmosphere that slows down GPS satellite signals as they pass through it, causing errors.

Troposphere
This is another layer in the atmosphere. The refraction of radio waves in the dry atmosphere and in water vapor causes errors.

Multibus
When radio waves emitted from GPS satellites are received, they are reflected by various objects such as the ground and structures. This phenomenon, called multipath, disturbs the radio waves and causes errors.

Of these, multipath is the most significant error factor because it limits the number of satellites that can be received and their placement among the satellites. The error varies depending on the performance of the GPS module itself, but a typical device equipped with a GPS module will have an error of about 10 meters in a good reception environment and about 100 meters in a poor reception environment.

However, smartphones have Wi-Fi, time correction, application location systems, and other systems that correct GPS, so using them together can further improve positional accuracy.

3. The Japanese Satellite Positioning System “MICHIBIKI”

To make GPS modules more accurate and stable reception, there is currently a Japanese satellite positioning system called MICHIBIKI, which has been in operation with four satellites since November 2018. Satellite positioning is possible with more than four satellites, but for stability, it is desirable to have more satellites visible.

MICHIBIKI, which is called the Japanese version of GPS, provides stable and highly accurate positioning by compensating for points where conventional GPS satellites’ signals are blocked and location information becomes unstable.

What Is a GPS Chip?

A GPS chip is a chip that is connected to or contains a GPS antenna that receives signals from GPS satellites and incorporates circuitry to calculate the current position.

GPS is an abbreviation for global positioning system, which determines a person’s location on the Earth by communicating with positioning satellites operated by the U.S. Department of Defense. A GPS chip is being actively developed for higher precision, smaller size, and higher performance.

Currently, in addition to the GPS satellites, the GNSS (Global Navigation Satelite System), which refers to the four satellite systems of Russia’s GLONASS, EU’s Galileo, and China’s Beidou, as well as signals from India’s GAGAN and Japan’s MICHIBIKI, etc., are also supported. 

Uses of GPS Chips

GPS was originally developed for military applications, such as guided missiles, but it has been opened up for civilian use and is now used to support navigation for ships and aircraft.

GPS chips have been developed and miniaturized, and are now used in portable devices such as car navigation systems, smartphones, and tablets. This enables map applications to provide navigation to current locations and destinations.

It is also used in wearable devices such as smartwatches as GPS loggers to check distance traveled, number of steps taken, and travel history. In addition to these, development for applications in the space business, etc., is also underway.

Principle of GPS Chips

GPS satellites contain a very precise clock (atomic clock) based on the frequencies of the spectral lines of atoms and molecules, and the signals emitted from GPS satellites mainly transmit this precise time and location information.

The distance from the GPS satellite can be calculated by multiplying the time of arrival of the signal from the GPS to the GPS chips by the speed of light. In other words, we can determine where the GPS chips are located on a sphere whose radius is the distance at that time.

This is done with multiple satellites, and the point where the spheres from all satellites intersect is identified as the current location. The more satellites received, the more accurately the location can be identified.

The satellites are equipped with atomic clocks and can transmit very accurate time, but the receiving GPS chips do not have an atomic clock. The receiving side is equipped with a common quartz clock, but it cannot be as accurate as an atomic clock, so it must receive from at least four satellites and correct the time by using the four variables x, y, z, and t.

Other Information about GPS Chips

1. High accuracy of the GPS Chips

Light travels about 185,000 mi per second, so even a 10 millionth of a second error results in an error of 98 ft. In addition to these errors due to time information, there are errors due to satellite positioning information, errors due to the ionosphere and moisture in the atmosphere, errors due to reflections from buildings and mountains, errors due to the small number of satellites that can receive the data, and other errors.

2. Miniaturization of the GPS Chips enables the following

The miniaturization of GPS chips has made it possible to mount them on the following devices.

GPS Trackers
A general-purpose GPS chip device about the size of a coin that can be attached to a variety of objects to transmit location information. It is small and lightweight (1″ x 1″, 0.5oz) and can be purchased for around 20 dollars.

Drones
As GPS modules have become smaller and less expensive, GPS-equipped drones have also become popular. Even models equipped with 4K high-angle HD cameras can now be purchased for the low 75 dollar range at major online retailers.

What Is a GNSS Module?

A GNSS (Global Navigation Satellite System) module is a module that uses signals from satellites to obtain positional information and other data.

It refers to the GPS of the United States, GLONASS of Russia, Galileo of the EU, BeiDou satellite positioning system of China, and QZSS of Japan, which are representative systems for determining positional information.

By using signals sent from various satellite systems, it is possible to measure position information with higher precision.

Uses of GNSS Modules

GNSS modules are used to measure a vehicle’s position, speed, and direction of travel information, as well as to acquire location information for mapping functions on smartphones. Other applications include tablets, smart watches, laptops, medical applications, smart agriculture, precision location, smart trains, robotics, autonomous vehicles, industrial automation, logistics and asset tracking, drones, agricultural machinery, and construction heavy equipment.

When selecting a GNSS module, considerations should include the size and cost of the module and the size of the signal received from the antenna and processed. Other considerations include shock strength against dropping for smartphones and tablet PCs, and heat and vibration strength for GNSS modules for automotive applications.

Principle of GNSS Modules

The position and time information sent from multiple satellites is received by the signal receiver. The distance between the satellite and GNSS is determined from the received time, the time the signal was transmitted, and the speed at which the signal is traveling.

On the other hand, signals transmitted by satellites are often weak, and various obstacles, environmental noise, and interference in the reception environment can hinder signal reception, making it challenging to determine accurate location information. Therefore, there are products that implement advanced signal processing to determine accurate position information.

Structure of GNSS Modules

The components of a GNSS module include a receiver, a low-noise amplifier, and a GNSS receiver. Weak signals emitted from satellites are received by the signal receiver and amplified by a low-noise amplifier.

The amplified signals are processed by the GNSS receiver to calculate position information. The position information is then sent to the device connected to the GNSS module for use in position-based applications.

Other Information About the GNSS Module

1. Main Error Sources of GNSS Modules

Although GNSS modules can provide high-quality position measurements by catching signals from satellites, errors can occur due to factors such as satellite orbit, satellite clock, ionospheric delay, tropospheric delay, receiver (antenna), multipath, etc. The reasons for errors caused by each factor are described below:

Satellite Orbit Factor
Positioning calculations are performed by receiving ephemeris data (satellite orbit data) and almanac data (satellite orbit history) from satellites. Ephemeris data is updated every two hours and Almanac data every six days. Therefore, during the periods when both data are not updated, the position must be estimated based on the most recent data, which may lead to errors.

Satellite Clock Factor
Data from satellites contains satellite clock information. There is a lag time between when the satellite clock information is transmitted from the satellite and when it is caught by the receiver.

Ionospheric Delay Factor
The ionosphere is a region between 50km and 1,000km above the Earth’s surface where solar activity causes variations in the type and density of gases. When radio waves from satellites pass through the ionosphere, the refraction of light causes a delay in the transmission speed.

Tropospheric Delay Factor
The troposphere is the area between the ground and 11km above the ground. When radio waves from satellites pass through the troposphere, as in the ionosphere, the refraction of light causes a delay in the transmission speed.

Receiver (Antenna) Factor
After the satellite information is received by the antenna, various factors such as cable, circuit, and radio delays, as well as the speed of positioning calculation operations and memory access speed, can affect the error.

Multipath Factor
Multipath refers to radio waves that bounce off reflective objects and thus are delayed behind directly incident radio waves. In the case of radio waves from satellites, there are cases where the output of multipath radio waves is larger than that of directly incident radio waves. In this case, the positioning calculation may be performed using the multipath data with higher output.

2. Positioning Method of GNSS Module

GNSS module positioning methods can be broadly classified into two types: single positioning and relative positioning.

Independent Positioning
In stand-alone positioning, signals from four or more satellites are received by a single receiver to perform positioning. The accuracy of single-satellite positioning is limited to 10 to 20 meters due to satellite clock factor errors.

Relative Positioning
Relative positioning performs simultaneous, independent positioning at the reference point for which precise coordinates are required and at the point to be measured. In this case, information from multiple receivers is used, enabling higher quality positioning than with stand-alone positioning.

What Is a ToF Sensor?

A ToF sensor is a sensor that measures distance based on the time it takes for a pulse of light to be reflected back from the surface of an object.

ToF sensors measure time and convert it into distance, so that the detection accuracy can be maintained at a constant level regardless of the distance.

ToF sensors are used to measure the distance to an object, as a level sensor, to locate and position objects, and to check the number of people in a space.

Uses of ToF Sensors

1. Recognition for VR and AR

ToF sensors are used for VR (Virtual Reality) and AR (Augmented Reality) recognition, which have become popular in recent years, because of their accurate measurement of distance from the object, enabling images to be displayed with a more three-dimensional effect.

2. Monitoring

ToF sensors can be used as level sensors to monitor machine lifts, monitor the amount of material remaining in tanks, check warehouse inventory, check the amount of material remaining in rolls, and check the availability of materials in automated warehouses.

3. Confirmation of Workpiece Seating

ToF sensor is used to confirm that a workpiece is seated on a jig in a production line.

4. Confirmation of the Number of Persons in a Space

The number of people in a specific space can be counted by the 3D ToF sensor. The distance to an object is converted into data, and AI is used to determine the number of people by identifying them.

5. Measurement of Object Dimensions and Volume

3D ToF sensor can be used to measure the dimensions of each part of an object and measure its volume.

6. Smartphone Face Recognition Function

Since ToF sensors can capture the image of an object in three dimensions even in dark areas and enhance the autofocus function, their application to face recognition functions in smartphones is expected to increase in the future.

Principle of ToF Sensors

The principle of the ToF sensor is relatively simple. First, a laser diode inside the sensor projects modulated near-infrared light. The near-infrared rays that hit the object and are reflected return to the light-receiving element in the sensor. The phase difference between the emitted and reflected near-infrared rays is converted into a time difference, and multiplied by the speed of the emitted light to determine the distance.

In addition to measuring the phase difference, there is also a method of directly measuring the time difference, which is superior to other sensors in that the ToF sensor can maintain constant detection accuracy regardless of distance and can operate with good depth accuracy even in dark environments.

Infrared or near-infrared light is often used for lasers, but it depends on the sensor, and some wavelengths are harmful to the human eye, so care must be taken depending on the application.

In the case of infrared or near-infrared lasers, the measurement point cannot be visually confirmed. A separate scope, guide laser, or other device is required to check whether the laser is irradiating the object.

Types of ToF Sensors

There are two types of ToF sensors: 1DToF and 3DToF.

1. 1DToF Sensor

1DToF sensors measure the distance from a sensor to a specific point. They are used in motion sensors and level sensors that measure the amount of liquid or powder.

2. 3DToF Sensor

3DToF sensors can acquire distance information with an image, just like a camera. It measures the distance to an object in the entire space.

Other Information About ToF Sensors

Advantages of ToF Sensors

1. Long-Distance Installation Is Possible
ToF sensors can be installed at a distance from an object because they can detect with high accuracy even at a long distance. They can be installed in locations that avoid the lines of movement of people and robots. For large objects such as automobiles, multiple ToF sensors can be installed for positioning from multiple directions.

2. High Degree of Freedom of Installation
The sensor itself is compact and can be installed in a small space. The irradiation direction can also be freely selected, such as up and down, horizontal, or diagonal.

3. Independent of the Surface Condition of the Object
The ToF sensor performs high-speed sampling and averaging processing, allowing stable detection regardless of the object’s color, material, etc., even if the amount of light received is insufficient.