powering your project
There are so many types out there, what to remember when browsing your local store or digging a box of recycled parts?
In this note, I would like to give you a clear concept of what is different and what is to be noted.
Note: I only cover mains power supply projects here.
First of all, you need to find out the specs you are looking for and they are all related to each other.
You can spend a few days looking for your ideal power supply through various folders, directories, websites, etc.
Most likely: it doesn\'t exist and you have to meet less needs.
For most people, this is the only consideration when choosing a power supply.
Of course, this is the most important thing. your project needs voltage and power. you can\'t change this.
However, you can change the way you provide it.
For example: if the Arduino needs 5 V and the motor needs 12 V, then a step-down converter is a good idea, not a PC power supply or 2 wall warts.
The cost looks simple, your junkbin is free and the store has a simple price tag.
But it is not so clear, efficiency has played a big role.
We need 5 V 0.
5 amps for Arduino project, the screen will be on permanently.
In your junkbin, you found an old 12 V Wall HDD that your Arduino accepts 7-
There are 12 V on the input, so you\'re done.
These old walls are usually only about 45% efficient and expensive.
Arduino reduces 12 v to 5 v using a linear power supply. You use 5V 0. 5A -> 5*0. 5 = 2. 5 Watt.
The power supply in Arduino converts 12 v to 5 v by changing the 7 v differential to heat.
This means that it is still 0 at 12 V. 5A, so 2. 5W becomes 6W.
The efficiency of the wall loft is 45%, so the 6 w output means about 13 w input (
The 45% of 13 w is 6 w).
Therefore, only 2 W out of 13 W used from mains.
5 w is actually used. 10.
5 w wasted on heat, the time wasted on heat in a year is about 92kWh.
The average kilowatt-hour price in Europe is about 20 cents, and the United States is about 12 cents. (
The dollar or euro is not important in these estimates)
That means you\'re wasting 11-
The power wasted in the free power supply is $18/euro per year.
A simple USB charger is about 70% efficient with a direct output of 5 v, reducing wasted power from 10. 5W to 1. 1W.
It\'s just 8 KW hours/year, or save more than 10 €/USD per year, it\'s enough to buy a USB power supply.
In the power supply project, the input is usually the power supply, but the power supply is different all over the world.
Power supplies around the world range from 110 V to 250 V, and everything between many \"host\" power supply projects is actually powered by the output of some other devices, such as servers.
Generally speaking, the power supply with a larger input range is less efficient.
Power supply with switch (
Such as pictures)
There is no problem.
Higher input voltage also reduces efficiency (
Too bad, I\'m in a country of 240 V).
The updated power supply gets better every generation.
This is mainly because the internal frequency of the power supply is getting higher and higher, which makes the power transmission more efficient.
Efficiency is the amount of power entering the power supply compared to the output power.
Here are the power efficiency data you may find.
Of course, these are rough estimates, and in general, these rules apply: efficiency also varies greatly depending on the amount of electricity consumed.
At about 75% of the load, you usually find that the power supply is the most efficient.
Don\'t try to use high power under low load, and under low load, efficiency will drop like bricks.
Do you do any audio/simulation in your project and you will really care about noise and ripple.
This is usually not important in digital design.
Ripple: how flat is the output voltage under load.
The ripple always has the frequency of the internal frequency of the power supply.
The transformer will always be at the power frequency (50/60Hz). Switch mode (
Updated adapter, computer supplies, open frame, etc)
Usually at 5-
The 150 kHz range, which usually changes if the power supply is under load.
This can be a show.
The plug of the audio system.
Noise: how clean the output signal is.
This is mainly based on the quality of the components used in the power supply and the working principle of the power supply.
The noise of the linear power supply is very low because there is no switching element in the power supply, which makes the design automatically absorb the noise in the system.
Switching power supplies work effectively by converting a small amount of energy into different voltage levels, and although this is very effective, a lot of noise is generated per switch action.
Use low level to filter ripple and noisepass filters.
If efficiency is important, but Ripple/noise is also important (
For example in an audio amplifier)
You can observe both linearity and switching at the same time.
For example, if you need 12 V, use a 15 V switch power supply and connect a linear power supply from 15 V to 12 V.
This will greatly improve the noise level.
The size of the power supply mainly depends on the output power and efficiency.
You need a larger power supply if the power supply is larger.
If the efficiency is higher, the power supply will be smaller for the same output power.
The power supply is always limited by the size of the transformer, but the higher the frequency, the smaller and lighter the transformer will be.
The smaller the parts, the greater the power in the same box.
A transformer of 1000 W with a volume of about 20 kg and a small table size.
The modern PC power supply of 1000 W is less than 5 kg, it is easy to install in the shoe box.
How durable/reliable should your project be?
The simpler the power supply, the more reliable it is.
The more industry it is, the more reliable it is.
The hotter the power supply, the faster the interrupt is.
Sorted by reliability: the single element that usually breaks first is the electrolytic capacitor in the filter.
These work on the water.
The liquid electrolyte in the tank will leak over time.
The hotter they are, the faster they fail.
There are so many things to pay attention to, I only touch the surface. Short summary
Interested in more information?