When I look at some schematics designed by others, I have some doubts that the designer will add some protection devices to the schematics. I would like to ask what external interference I should pay attention to in circuit design that may cause circuit failure, and what devices can be used to protect it? I hope you can give me some Pointers.

 

What kind of circuits are you talking about?

What protection from outside interference would you suggest for a circuit consisting of a battery, resistor and LED?

 

Are You asking for protection against catastrophic-failure ?.
or are You asking for protection against electrical-"Noise" which could cause the Circuit to malfunction ?

Either one of the above problems usually requires custom modifications or additions to the Circuit.
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Refer to the white paper if available.

 

When I look at some schematics designed by others, I have some doubts that the designer will add some protection devices to the schematics. I would like to ask what external interference I should pay attention to in circuit design that may cause circuit failure, and what devices can be used to protect it? I hope you can give me some Pointers.

This is a very broad and wide topic. You need to define the type of external interference. There are many different types of interference.
1) Powerline noise
2) RF noise, EMI
3) alpha particles
4) high energy cosmic and gamma radiation
5) geomagnetic storm, CME (coronal mass ejection)

 

In many cases the susceptibility to electrical interference is related to the circuit impedance, and usually related to the action threshold proximity to the resting voltage level. So that can provide you with a basic knowledge.

 

Parts cost money.

You protect against things that you will encounter in a reasonable situation, beyond that, you are wasting money.

 

When I look at some schematics designed by others, I have some doubts that the designer will add some protection devices to the schematics. I would like to ask what external interference I should pay attention to in circuit design that may cause circuit failure, and what devices can be used to protect it? I hope you can give me some Pointers.

Some folks who create electronic circuits tend to "protect" against all kinds of voltages that may not even have any effect at all, and that may not even be possible in the circuit involved. There often is a big distance between theory and reality.

 

When I look at some schematics designed by others, I have some doubts that the designer will add some protection devices to the schematics. I would like to ask what external interference I should pay attention to in circuit design that may cause circuit failure, and what devices can be used to protect it? I hope you can give me some Pointers.

What country are you in? Too many times I see people doing technical things without checking legal first. In the USA, most electronic devices are required to accept any and all interference per the FCC. How you can protect your circuits against that is through shielding that grounds, smart trace design in PCBs that alleviate inductance or reactance issues, as well as understanding exactly what current levels you should be using to drive circuits at in order to 'overcome' noise, but not ridiculous.

An example of someone not checking legal-- I saw a video on YT the other day where someone added avionics to their model rocket.... While I admire this, and I think it's a wonderful use of electronics and something I'd like to do myself, it never occurred to them to check applicable laws. In the United states it is illegal (per FAA & Military) to add avionics to model rockets (or any kind of 'guidance' system) because that converts its classification from 'experimental model rocket' into 'missile.

Be smart people.

 

Could it be that what "B.M." saw on YT was in fact a missile?? Back in the early 1940's era there was a glide-thing with remote controls and a TV transmitter in it. That was the ROC-BIRD. It was described in a book that I got at a yard sale. Very interesting, what was being done over 80 years ago.

 

What kind of circuits are you talking about?

What protection from outside interference would you suggest for a circuit consisting of a battery, resistor and LED?

What I want to know is the specification that should be paid attention to in the design of DC power supply circuit, such as BUCK circuit. I am trying to learn English, and sometimes the meaning may be a little wrong, thank you very much.

 

OK, and unfortunately switching power supplies are probably the most challenging system to design, of all circuits. That is because EVERY component is important to the design, and also every connection matters, both resistance and inductance. So every component matters, because in the details, even what looks like a simple circuit is complex.

None of that has anything to do with external interference, though.

 

Copper tape wrap and solder a wire from tape to gnd. Make sure tape that overlaps has a small solder joint to keep the copper gnd plane continuous. How you wrap "it" depends on how it's enclosed. With plastic enclosures where I need some RFI blocking, I will line the enclosure with copper tape and gnd the tape.

Or, a metal enclosure that electrically seals well and has hermetically sealed connectors.

I wonder if ckt is in mineral oil how it filters "interference".

If the noise (interference) is very highy frequency, ~GHz+, then the method used will change.
Magnetic noise, use Mu metal.
Powerline noise, use a Murata filter.
If it's backscatter wavelength stuff, blocking with metal is also a challenge.