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There are several types of power supplies. So you have to choose the right power source for what you will be doing. That doesn't mean the power supply must be selected and connected properly.
The following are typical types of power sources.
| Power source type | Power supply feature | |
|---|---|---|
100 Vac (AC) | AC power source | A power source that produces alternating current, such as a commercial power source. |
12 VDC (DC) | DC power source | The power source produces direct current, including the primary battery and the rechargeable battery. |
| Switch power source | The power supply converts commercial power into direct current using a switching circuit, etc | |
| Serial power supply | One of the linear power supplies converts commercial power to direct current using a series regulator. | |
| Reference power source | The power supply produces a constant voltage regardless of mains voltage, temperature, element changes, etc | |
It is very important to check whether the device operates on direct current or alternating current. Device connection works by AC power source with DC power source or vice versa may damage the device or power supply. Even if a DC power supply is required, you should not use it near heat-sensitive devices because series power is linear and generates heat. On the other hand, switching power supplies can prevent heat generation but they create a lot of noise, so you should avoid connecting devices that may malfunction due to noise.
Additionally, if the device is susceptible to voltage fluctuations or requires a stable power source for measurements, a reference power source should be used. In fact, the reference power supply is also used as a switching power supply to stabilize the output voltage.
After choosing the right power source, you need to check the operating range. There will be problems connecting a device operating at 12 V to a power supply with an output voltage of 120-240 V. You must ensure that the output range of the power supply covers the voltage and current you want to use. Of course, if the output is too large, it will lead to equipment damage. Even if it actually works, the resolution to make performance measurements may not be enough.
Best of all, you don't have to be careful about the power source. It is important to check the load for connection. Check that the load characteristics of the connected load such as resistive load, inductive load, capacitive load and LED are suitable for the purpose.
If you pay attention to the above, the choice of equipment is fine. Then the wiring is connected, but if high voltage or current is used, the capacity of the wiring material may not be enough. If there is insufficient power, the wiring will generate heat and the measurement will not be performed accurately. In addition, the insulation of the wiring can melt and, in the worst case, it can catch fire. Try to use a power cord suitable for current and voltage.
Heat generation due to lack of wire capacity can lead to fire.
Use conductors suitable for current and voltage.
Then, when connecting, check the polarity. Some light bulbs are connected without regard to polarity, such as small light bulbs used in science experiments, but diodes and the like will not work if the polarities are connected in reverse. When connecting a large number of circuits, they will not work properly unless they are connected while checking the polarity of each circuit.
Then, consider whether to connect the circuit to ground (GND) or not. By connecting to ground, there will be a stabilizing effect of the voltage difference and a noise reduction effect. Ground is usually used for fixed devices but in some cases it can be a metal frame.
When the short bar is connected, the potential is based on Ground (GND).
When not grounded, the potential is independent (floating).
Next, let's introduce some things to keep in mind in addition to preparing equipment. You probably won't just be working with low voltage equipment. When handling high voltage equipment, you need to be careful about the working environment. First, don't put anything other than what you need in your workspace. It can cause errors, if equipment is left cluttered in the workspace, work efficiency will decrease. Also, as explained earlier, if the voltage is too high, it can catch fire. If flammable substances are left in the workspace at this time, a fire will occur. Even if it does not cause a fire, if the insulating film melts, there is a risk of electric leakage and electric shock caused by it. Therefore, to prevent electric leakage and electric shock, it is necessary to organize the working environment and work on insulating and fireproof materials.
It's better to consider fire prevention just in case. Fires involving electrical equipment include fires caused by re-energization. A re-energized fire occurs when an electrical device is energized. People often know when an earthquake occurs that there is a power outage, but when the power is restored, the collapsed electric stove ignites flammable materials in the surrounding area. Be careful in the workplace, especially when equipment comes into contact with flammable substances. There is also a risk of electrical leakage if the workspace is damp.
In addition, various precautions should be taken against electrical fires. It can also be caused by stains that occur when a dusty plug is energized while still plugged into an electrical outlet, or an electrical short circuit caused by wiring that is not properly insulated.
Take necessary measures to prevent electrical fires. Avoid monitoring and short circuits due to poorly insulated wiring, which can also cause a fire or explosion.
For details, refer to “Providing Stable AC Power” section.
Don't forget to pre-check the operation before turning on the power switch of the power supply. Unless you work alone, if you work with multiple members, there may be components that are working at the wiring point or short circuited. Therefore, to avoid accidents, it is necessary to do a general check and check the operation before connecting the load. In addition, if you connect a power source that has not been used for many years instead of a power source that you usually use, you need to check in advance whether the operation of the power source is appropriate. Due to a power supply failure, the rated power may not be reached or ripples may appear due to improper rectification. Additionally, unwanted voltage fluctuations and frequency fluctuations may occur, so make sure that they do not occur.
Now that the power supply has been tested and all the list of workplace safety items have been cleared, the power output switch is finally turned on. However, there are some items that need to be checked before operation. For example, check voltage and current settings. If the voltage and current settings remain large, high voltage will suddenly be applied to the connected device. Although it depends on the content of the test, it is recommended to first narrow down the voltage and current and then gradually increase it. How can we increase voltage and current gradually and safely?
There is CC control which gradually increases the voltage while continuously flowing a constant current and CV control which increases the current while applying a constant voltage. There are also CV/CC controllers that operate in combination of both. CV/CC requires fine control but it is very useful as a method of providing stable power.
Even so, experiments can damage equipment and payloads. To prevent this situation, it is necessary to arrange so that there is no unwanted voltage, or if there is electricity, the wire can be cut so that the current does not flow for a moment.
For example, insert a limiting resistor to prevent the current flowing through the LED from exceeding the maximum current value of the chip. When using a 12 V battery in a vehicle, if two 5 V LEDs are used in series, the required voltage is 10 V, i.e. over 2 V. In this case, install a limiting resistor corresponding to This resistance is above 2 V (or higher).
The resistance value of the limiting resistor is calculated according to the following equation.
Resistance value = Voltage -> Current
So, prepare resistors with different resistance values depending on the current flowing through them. There is also a method of controlling voltage using a diode (Zener diode). Additionally, by incorporating a fuse that can blow up the built-in alloy parts when excess current flows through, both current and voltage can be controlled.
Semiki summarizes and details at AC and DC programming sources