yingshaoxo_electronic_power_law
Let’s start with the power supply or power source you have from home
Normally, you would have AC220V or AC110V voltage power source at home.
You can verify it by using multimeter.
It is alternative_current because the two line(two holes) you got sometimes is positive end, sometimes is negative end, it changes over time.
Usually people call this kind of power source AC(Alternating current).
Let’s talk about DC 5V battery or USB 5V power supply
What is DC? DC is Direct_Current.
For DC 5V or USB 5V power, it is normally used to charge your mobile phone or drive some USB devices, like keyboard, mouse or USB storage.
For this kind of power supply, it has fixed positive and negative end. If you use multimeter to test its voltage, you’ll always get a positive number or negative number when you fix the test line.
What kind of power supply has the most big power?
Some people would say “The higher voltage, the greater!”. That is a lie.
Some people would say “The higher current, the greater!”. That is a lie.
Actually, just image the water flow, the current defines the size of the water pipe, the voltage defines the driving force to the water.
When “voltage is high, current is low”, it is like “driving force is big, but pipe size is small”, the end water would be small. Power is likely to concentrated into one point. It can be a damage one, like lightning, but only damage a small point. And people normally will limit the water storage or size in source, so as long as the water running out, the end side would have no water, so no damage. An example would be “20kv voltage booster”, it sounds scary but has almost no damage.
When “voltage is low, current is high”, it is like “driving force is small, but pipe size is big”, the end water is big. Slow but powerful can be an example of this. If you have a 5V DC motor, but you give it a big current, it would be unstoppable as long as the line didn’t get burned. (I mean, you can’t stop it with your pure hand)
For 5V mobile phone charging, the current it needs is usually 1A to 3A.
How much “water” or electricity we need for our devices?
Normally, for all those electricity devices, they will have a paramater called “watt”.
For example, for a microwave, it has a paramater of “1500 watts”.
watt = current * voltage
If you have power supply of AC220V, 1500 watts means the microwave will use “1500/220=6.8 Ampere”, a 6.8A current.
You could give the microwave a AC220V but 0.1A power source, but the microwave won’t work anyway.
Normally the home power source is AC220V, 220A.
How to convert AC220V to DC220V?
Use rectifier circuit.
Or to be specific, use “diode”. Because diode will only allow current to go through in one direction with no coming back. (Diode works similar to “one-way air valve”.)
By using diode, we could successfully convert Alternating_Current(AC) to Direct_Current(DC).
How to convert DC220V to lower voltage?
Normally we use “resistor”, resistor is like a small size pipe, it will slow down the current and reduce the voltage.
For example, if you have a DC220V power source, and in the same line, you also has a 1Ω(omega) resistor, the final current would be “220V/1Ω=220A”.
But if in the same line, you has a 2Ω resistor, the final current would be “220/2=110A”.
If in the same line, you has a 20Ω resistor, the final current would be “220/20=11A”.
The same thing also works for voltage. Because if the water already leaks from other branch, it would have less force in this branch, so the voltage would get reduced. Some people call this behavior as “Resistors in parallel will reduce voltage”.
If you want to know exactly how much current or voltage is at the end line, I suggest you to use some “realtime circuit simulator”, for example, “CircuitJS1” or “EveryCircuit”.
How to convert AC220V to AC24V?
Use a “AC220V to AC24V Power transformer” to convert the AC220V to AC24V.
How to convert AC24V to DC5V?
First use a diode to convert AC24V to DC24V first. (If single diode is not stable enough, you could use a full_wave_bridge_rectifier, which uses 4 diode)
Then use some resistors to convert it to DC5V.
If you don’t know how many resistors you should use in here, you can also use a “5V zener diode” to let “more than 5V current” go back to its source, so the end power will always be 5V.
Zener Diode can indeed be used for DC voltage conversion, but it requires a 1k resistor in series.
When a Zener Diode is connected in parallel to the output, if the voltage is higher than the breakdown voltage of the diode, the diode will send the high voltage back to the source power supply. As a result, only a voltage less than the breakdown voltage remains at the output end.
In addition, you can also achieve DC voltage reduction by directly connecting two large resistors in series to the circuit. (It’s just not as stable as zener diode, because the final effect depends on the load)
The same principle applies to the boost circuit. It just needs a boost circuit in front to convert the small voltage into a large voltage.
#electricity #yingshaoxo
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Zener Diode 确实可以用来做DC电压转换，但就是得串联一个1k电阻。
当把 Zener Diode 并联到输出端时，如果电压高于该diode的击穿电压，diode则会把高电压送回源电源。如此一来，输出端就只剩小于击穿电压的电压了。
另外，你直接串联2个大电阻到电路，也能实现DC降压。(只是不如zener diode稳定，因为最终效果要看负载)
升压电路同理，只是要前置一个升压电路，先把小电压转成大电压
#electricity #yingshaoxo
More stuff to know
relay
relay can be used to use 5V to control 220V.
When 5V is giving as a signal, 220V will get send out.
When 0V is giving as a signal, 0V will get send out.
Battery
5V battery is all you need. Most devices say they need 8V, 12V, but in the end, 5V could also drive them, if you got a big current.
If you can’t do it with direct 5V, you could put two 5V battery into one line to get 10V battery.
Capacitor
This is normally used after AC to DC circuit, in a parallel way, the capacitor in here will absorb some AC to let the DC more stable.
You shouldn’t miss up with its positive and negative side unless it is CBB capacitor.
A simple diode could be used to prevent capacitor release power in a wrong way.
Go to explore
Do whatever you want, keep safe.
Author
yingshaoxo