Grandwatt Solar& Hybrid Products
include Solar Light Tower, Hybrid Light Tower, Mobile Surveillance Tower
and Solar generator unit.
Mobile
Surveillance Tower is a solar tower with camera, with zero COâ‚‚ emissions
and zero noise, zero operating costs, it is powered by 2*200 Ah Lithium battery
and 2*455 W Mono, it can last above 55 hours.
Trailer Mobile Light Tower,Solar Lighting Tower Grandwatt Electric Corp. , https://www.grandwattelectric.com
Solar light tower
is efficient and delivers high performance light tower, giving workers good
visibility while allowing sites to increase sustainability with zero COâ‚‚ emissions
and zero noise, zero operating costs (diesel fuel, maintenance, labor), it is
100% renewable energy, stronger structure can load more power solar panels and
batteries, patented rotating mechanism can adjust angle of solar panel to best
align with the sun's location to achieve maximum solar yield.
Hybrid light tower
is an advanced lighting tower, it can save 40% fuel, save maintenance, save
labor. It operates from the latest solar and battery combination, backed up by
a small fuel-efficient diesel engine. Utilizing latest, hybrid technology,
provide less consumed power than traditional towers for huge fuel savings and
reduced COâ‚‚ output.
1-10
1. What is the forward bias of the diode? When a positive voltage is applied to the p-type side and a negative voltage to the n-type side, it's called forward bias. This allows a significant increase in diffusion current. On the other hand, reverse bias increases drift current, which is caused by minority carriers, resulting in a reverse saturation current.
2. For low-frequency signals, the thickness of the resistance wire determines how much current flows through it. However, the resistance of copper wires is negligible, so it doesn't affect the current flow. Exceptions may exist in special cases.
3. A MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor) is a device that relies on majority carriers for conduction. Unlike bipolar junction transistors (BJTs), where both majority and minority carriers participate, MOSFETs are self-isolated, eliminating the need for isolation islands. This makes them ideal for large-scale integrated circuits. They are also voltage-controlled devices, requiring almost no current at the control terminal, making them easy to integrate.
4. How can you identify the C, B, E terminals of a transistor? And how to determine the G, D, S of a MOSFET? You can check the data sheet or use a multimeter in diode mode. If the reading shows a voltage when P is connected to the positive and N to the negative, you can determine if it's an NPN or PNP type. Then, using the HFE mode, you can measure the gain. For a MOSFET, connect the gate to the drain and see if there is a reading. If not, it might be damaged.
6. DC feedback stabilizes the static operating point, while AC feedback improves the amplifier's performance.
7. The relationship between capacitors and resistors is reversed compared to inductors. Inductors behave like resistors, but mutual inductance introduces differences. Further clarification may be needed.
8. Oscilloscopes often display multiple cycles of a signal on the screen, but too many cycles may not be shown.
9. A common-base amplifier is a non-inverting amplifier with high output resistance and a voltage gain of 1, known as a "follower." A common-emitter amplifier is a non-inverting amplifier with high input resistance and a current gain of 1, referred to as a "voltage follower." A common-collector amplifier is an inverting amplifier with high voltage and current gain.
10. In a full-wave bridge rectifier, the average output voltage is 0.9 times the RMS value of the input voltage. Therefore, the average output current is 0.9 times the RMS input voltage divided by the load resistance.
11-20
11. The two probes of an oscilloscope are usually grounded. When using dual traces, ensure both grounds are connected, especially at high voltages. Not all oscilloscope probes are grounded, some are isolated.
12. To test a MOSFET, check the G, D, S configuration. Use a multimeter to apply voltage across G and S, then check DS. Be cautious, as the G-S capacitance can be small, and static charge can damage the device.
13. U-disk cannot handle many small files; it may become slow or stuck. Compressing files before transferring is recommended.
14. Before measuring with a multimeter, understand what signal you're measuring and select the correct range.
15. TVS (Transient Voltage Suppressor) tubes have a very fast response time.
16. Review transistor and op-amp parameters regularly, as they are crucial.
17. Understand the different working states of a transistor thoroughly.
18. When testing a circuit, divide it into power, input, and output sections. Check each part carefully. Also, ensure the measuring instruments are set correctly.
19. Waveform superposition follows the principle Uac = Uab = Ubc.
20. Chokes block AC and allow DC. Low-frequency chokes suppress AC, while high-frequency chokes suppress high frequencies.
21-30
21. Amplifier circuits can be either DC-coupled or AC-coupled. The difference should be clear.
22. The basic transformer turns formula is N = V / (4.44fBmS). The derivation is covered in learning materials. Some formulas may use 4 instead of 4.44. For switching power supplies, the core volume calculation formula is Vcore = 4ueP/fBm.
23. The relationship between β (AC gain) and hfe (DC gain) in a transistor: β is frequency-dependent, while hfe is a DC parameter.
24. Light loads have low resistance, while heavy loads have high resistance. Current sources differ from voltage sources.
25. Network cable crystal head standards: straight-through is 586B, crossover is 586A and 586B. Pins 1, 2, 3, 6 are used for data, while 4, 5, 7, 8 are for telephone lines.
26. Inductive loads lag behind the voltage, capacitive loads lead, and resistive loads are in phase.
27. Air conditioning lines typically use 16A, while ordinary lines use 10A. 1mm² cables carry 4A, and 2.5mm² is standard.
28. Connect the modem to the router, which has switch/hub functionality. Hubs require dual network cards for internet sharing.
29. Capacitor charging follows u = q/C. The charging equation is u = U(1 - e^(-t/RC)). After t = RC, the capacitor is about 63% charged.
30. The pin arrangement of the 78/79 series voltage regulator is 1-3-2, with pin 2 always being the output.
31-40
31. To get 24V from a 7824 regulator, the input needs 28V DC. Convert this to AC using 28/1.2 = 23.3V.
32. Power supplies and amplifiers generally have low output resistance for better load capacity.
33. In op-amp circuits, components like 22μF capacitors provide 100% negative feedback, stabilizing the DC working point.
34. Problem-solving steps include understanding the background, listing technical specifications, system partitioning, estimating time, selecting instruments, identifying challenges, designing hardware, writing software, PCB debugging, and final testing.
35. Multimeters may show distorted waveforms if the battery is low.
36. Use the secant method to locate short circuits on a PCB.
37. Instrumentation amplifiers must have a connection between input and output to avoid floating common-mode voltages. Adding a 1μF capacitor between grounds can reduce interference.
38. Protel tips: Disable network access for certain software. Set up proper grid sizes and layers. Use cross-selection for component placement. Ensure values are transferred from schematic to PCB.
40. Date and version numbers should be added to PCB designs.
41-50
41. A potentiometer's resistance changes based on rotation direction. Clockwise decreases resistance, counterclockwise increases it.
42. Assembly language requires manual header file inclusion, while C uses #include directives.
43. An in-circuit emulator replaces the MCU on the target board for testing.
44. Export component lists in Protel using RRI and save as XLS.
45. A 160×128 LCD module uses a 16×16 Chinese character grid with 10 columns and 8 rows.
46. Multimeter DC mode measures average values, while AC mode measures RMS.
47. Differentiate between self-excited and parasitic oscillations.
48. Learning experience with single-chip microcontrollers: Use C compiler to generate machine code. Keil51 setup includes project creation, source addition, compilation, and hex generation.
49. Understand the 89C51 minimum system, including oscillator, reset, and LED display.
50. Dissecting a PCB involves mapping components to the schematic and analyzing each chip.
51-60
51. Small signals should avoid switching power supplies. For example, a 10A constant current source through a 0.001Ω resistor.
52. Switching power supply indicators include current regulation rate, voltage regulation rate, ripple voltage, efficiency, and temperature characteristics.
53. Magnetic saturation occurs when the magnetic flux in an iron core reaches a maximum and no longer increases with current.
54. Transistor saturation happens when Vce is low, and increasing Ib does not change Ic significantly.
55. Accuracy of 0.1% means 0.1% tolerance.
56. A capacitor stores energy as ½CU², while an inductor stores ½LI².
57. Common-mode voltage is the average of the two inputs, while differential-mode voltage is the difference.
58. Excitation current is the primary current when the secondary is open. It is small due to high inductance.
59. Emitter amplifiers avoid distortion by adjusting RB1, RB2, RC, and Re for stable bias.
60. Rail-to-rail op-amps have different output structures compared to standard op-amps.
61-69
61. Capacitor charging and discharging are DC processes, not related to RC oscillators. RC oscillator frequency is f=1/(2Ï€RC).
62. High input impedance reduces loading on the signal source, while low output impedance improves driving capability.
63. Electromotive force in a magnetic field depends on magnetic flux change, velocity, and direction. Ampère’s law relates magnetic field strength to current.
64. Integral and differential circuits require RC networks. Resistors limit gain and prevent oscillation.
65. Inductive excitation stores energy, while degaussing releases it.
66. Inductive reactance and capacitive reactance vary with frequency, while inductance and capacitance remain constant.
67. Capacitance and inductance formulas: V = L(di/dt) and V = C(du/dt).
68. Inductor open circuit generates high voltage, while capacitor short circuit causes large current. Both can damage components.
69. Motor current increases with load, leading to overheating and insulation breakdown. Motors are not purely resistive but have inductive properties.