Good day, everyone! I have a question to confirm something. I'm working on a project that consists of a Raspberry Pi, ESP32, an A4988 motor driver for a stepper motor, and a 5-inch Raspberry Pi LCD screen. Is it okay to use this centralized power supply to power all these components, even though it provides 12V at 10A? I plan to use a buck converter to step down the voltage to 5V. Will this setup be safe, given that the centralized power supply has a higher amperage rating than the components require? I want to use a centralized power supply so that I only need to plug in one thing into the outlet.
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Sure, you can do that.
The key thing is to not "daisy chain" your supply connections; rather, connect each thing directly back to the power supply.
This is known as a "star" connection.
You could add fuses to the individual connections.
You should alwsys have extra current capacity in your power supply. A properly built circuit will draw only the current that it needs. Power supply manufacturers often are enthusiastic with thier specifications. Running a supply near it maximum is not good practice.
Get a supply that will provide twice the current needed by the project and the highest votage required. The use DC-DC converters (switch mode buck converters) to drop to the votages for the other components.
The advice from @awneil on star grounding is very good. Run grounds back to the big supply ground. The point being that all grounds are at the exact same potential (voltage).
and not just the grounds - also the positive feeds.
@Newbie1.1.1 - consider the following:
That's what I mean by a "daisy chain"
When you connect like this:
- the current in Wire 1 is I1 + I2 + I3 + I4
- the current in Wire 2 is I1 + I2 + I3
- the current in Wire 3 is I1 + I2
This means that all the spikes & glitches from all the loads will be "seen" by Wire 1.
This will cause voltage drops - so Load 1 will have its supply "disturbed" by all the other loads.
You may well get away with this if the loads are just light, well-behaved items like Arduinos - but it becomes a real problem with heavy and/or noisy loads like motors, solenoids, etc.
You will find loads of posts here (and on similar forums) where people complain that everything works fine until the motor starts...
Instead, a "star" connection looks something like this:
So now each wire carries only the current from its own load - thus minimising the impact from other loads.
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Hi, thank you for your response 
Is it required to use a fuse or is it just optional? Another thing is, what kind of fuse should I use for my connection?
10A could burn the kind of 7/0.2mm wires you'd use with Arduinos - so wouldn't be a bad idea.
The idea of fuses is to protect the wiring, so any low-voltage fuse rated suitably for your wire would do.
That looks OK.
One thing to note with switch-mode power supplies like that is that they tend to have a minimum load - so you also need to check that you're not under-loading it!
If the small red board is just a sensor (or suchlike) taking only tiny currents, it might make more sense to power it from the Arduino...
EDIT
All of those things should work off 5V - so why are you using a 12V supply? 
If the small red board is just a sensor (or suchlike) taking only tiny currents
That's the A4988 motor driver.
All of those things should work off 5V - so why are you using a 12V supply?
Right now I only have 12V supply (without adjust) and I can't find any 5V supply in our place 
Another thing, sorry for too much asking. May I ask, what would be the circuit diagram when I put the fuse on each load? I mean, where should I put that? Is it before the buck converter? Or after the buck converter before the loads?
Ah - right. You forgot to show the motor!
Again, the fuses are really to protect the wires - so put fuses in the red wires, close to the power supply.
Maybe get something like this - for the automotive blade style fuses:
There are also polyfuses, like the one on an Uno, that open on an over current then self reset, unlike a glass or auto blade fuse that must be replaced.
The A4988 requires a minimum of 8V to work.
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Okay. Thank you. It should look like this right?
And since my power supply is 10A, what would be the specs of the fuse that I will be using? Is it 10A fuse also?
But I am using ESP32. I think I should use a fuse holder for glass so it will be easy to replace.
The A4988 requires a minimum of 8V to work.
Okay, thank you for the info.
Again, the purpose of those fuses is to protect the wires - so the fuses need to be rated no more than the rating of the wires you use.
The whole point of the Poyfuse is that you don't need to replace them - they reset themselves.
Glass fuses take time to blow. Way more time than it takes to kill a processor or other electronic device. Like @awneil says, fuses protect wires and, hopefully, prevent fires. Only good practices and careful work protects electronics.
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Is it a good choice to use polyfuse for my connection?
That's entirely up to you - and your electrical assembly skills:
You'd need a small board to mount them on, and it would require soldering.
Holders for the glass & blade types are available that don't require soldering
Okay thank you very much for your help, also to you @groundFungus
You are welcome.