Ten Daily Electronic Common Sense-Section 9

What are the data exchange instructions?

Data exchange instructions have the following two: SWP – word data exchange instructions; SWPB – byte data exchange instructions.

The characteristics of the middle layer?

1. Hardware Correlation Because the hardware environment of the embedded real-time system has application relevance, and as an interface between the upper layer software and the hardware platform, the BSP needs to provide a method for operating and controlling specific hardware for the operating system.
2. Operating system dependencies Different operating systems have different software hierarchies. Therefore, different operating systems have specific hardware interface forms.

What are the basic characteristics of CPLD?

• The main features are as follows:
  1. High-performance erasable devices using a second-generation multi-array matrix (MAX) structure.
  2. The delay between pins is 6ns, which can reach a working frequency of up to 151.5MHz.
  3. The number of integrated density gates can reach 1000, and the number of available gates is 600.

What are the applications of LED displays (screens)?

The application of LED displays has been very extensive. In the stadium, the large-screen display system can realize the functions of the game and the scores, time, and wonderful playback.

In the transportation industry, the road operation can be displayed.

In the financial industry, it can be displayed in real-time.

Financial information, such as stocks, exchange rates, and interest rates; in commercial post and telecommunications systems.

What are the disadvantages of the quasi-synchronous digital system?

The system structure is complex, the number of hardware is large, and the cost of the upper and lower circuits is high; there is no worldwide standard; the device does not have a unified optical interface standard, which limits the flexibility of networking.

Which three devices are used on the ZigBee network?

• Network Coordinator
• Full-featured device
• Reduced Functional Device

Varistor parameters:

1. Nominal voltage (V): refers to the voltage across the varistor when passing 1mA DC current.
2. Voltage ratio: The ratio of the voltage value generated when the current of the varistor is 1 mA to the voltage generated when the current of the varistor is 0.1 mA.
3. Maximum limiting voltage (V): refers to the highest voltage that can be tolerated at both ends of the varistor.
4. Residual voltage ratio: When the current through the varistor is a certain value, the voltage generated across it is called the residual voltage of this current value. The residual voltage ratio is the ratio of the residual voltage to the nominal voltage.
5. Flow capacity (kA): Flow capacity, also known as flow capacity, refers to the maximum pulse (peak value) allowed to pass through the varistor under specified conditions (specified time interval and number of times, applying standard impulse current) current value.
6. Leakage current (mA): Leakage current, also known as waiting current, refers to the current flowing through the varistor under the specified temperature and maximum DC voltage.
7. Voltage temperature coefficient: refers to the rate of change of the nominal voltage of the varistor within the specified temperature range (temperature is 20°C to 70°C), that is, when the current through the varistor remains constant, when the temperature changes by 1°C , the relative change in voltage across the varistor.
8. Current temperature coefficient: refers to the relative change of the current flowing through the varistor when the temperature changes by 1°C when the voltage across the varistor remains constant.
9. Voltage nonlinear coefficient: refers to the ratio of the static resistance value to the dynamic resistance value of the varistor under the action of a given applied voltage.
10. Insulation resistance: refers to the resistance value between the lead wire (pin) of the varistor and the insulating surface of the resistor body.
11. Static capacitance (PF): refers to the inherent capacitance of the varistor itself.

What are the disadvantages of speed regulation by changing the number of pole pairs?

1. A set of windings can only change two pairs of magnetic poles. One motor can only put two sets of windings, so there is only a maximum of four speeds.
2. No matter what kind of connection operation, it is impossible to get the best running effect, that is, its working efficiency will decrease.

What are the advantages and disadvantages of solid-state relays?

• Advantages：
  1. It has been widely used in numerical control and automatic control. Due to the use of optocouplers, the power required for the control signal is extremely low (about ten milliwatts can work normally), and the required control level is compatible with common integrated circuits such as TTL, HTL, and CMOS, and can be directly connected. This makes SSR widely used in numerical control and automatic control equipment. To a considerable extent}: can replace the traditional “coil-reed contact” relays.
  2. Reliable work and long life. SSR does not have any mechanical action and no contacts at work, so it has the advantages that a series of contact relays do not have, namely reliable operation, long life, and no sparks during the action.
  3. No action noise, vibration resistance, and mechanical shock resistance.
  4. The installation position is unlimited.
  5. It is easy to be potted with insulating and waterproof materials to make a fully sealed form, and it has good moisture-proof, mildew-proof, and anti-corrosion properties; it also has an excellent performance in explosion-proof and ozone pollution prevention. These features make SSR useful in the military (such as aircraft, artillery, ships, and vehicle-mounted weapon systems), chemical industry, underground coal mining, and various industrial and civil electronic control equipment applications, with technical advantages beyond contact relays.
  6. SSR can also withstand surge currents about ten times the rated current.
• Disadvantages：
  1. There is an on-state voltage drop. This is because when the PN junction is turned on, there is a certain voltage at both ends. The on-state voltage drop of the SSR is generally less than 2V.
  2. There is an off-state leakage current. This is because when the PN junction is turned off, a certain reverse current still flows. Off-state leakage current is generally 5 ~ 10mA. In use, on-state voltage drop and off-state leakage current should be considered to avoid malfunction when controlling high-power executive devices.

What is the turn-off thyristor?

Gate thyristor GTO (GateTurn-Off Thyristor) is also known as gated thyristor.Its main feature is that the thyristor can turn off itself when the gate is added with a negative trigger signal.

As mentioned above, after the ordinary thyristor (SCR) is triggered by the gate positive signal, the signal can be maintained while maintaining the on state.The thyristor can be turned off to overcome the above defects.

It not only retains the advantages of high voltage resistance and large current of the ordinary thyristor, but also has the self-shutdown capability and is convenient to use.

It is an ideal high-voltage, high-current switching device.GTO’s capacity and service life exceed the giant transistor (GTR), but the working frequency spinning is lower than the GTR.·

The turn-off thyristor is also a PNPN four-layer three-terminal device. Its structure and equivalent circuit are the same as ordinary thyristors. Therefore, Figure 1 only shows the shape and symbol of the typical GTO product.

Most of the high-power GTOs are made in modular form.Although the GTO and SCR have the same trigger-on principle, the shutdown principle and the shutdown mode are quite different.

An important parameter of TO is the turn-off gain, βoff, which is equal to the ratio of the maximum turn-off current IATM of the anode to the maximum negative current IGM of the gate.

The formula βoff=IATM/IGMβoff is generally several times to several tens of times. The larger the βoff value, the stronger the ability of the gate current to control the anode current.