Efficient Analysis of Schematic Electronic Circuits

[jcisd]

Hi!

I'd like to ask you if you can help me on this point...

I see many schematic electronic circuits on the web, for several applications. Some are very basic, some are not.
Each time I see a schematic circuit I try to understand it, how it behaves... To analyse it...

Biut with the big ones, I'm oftenly lost, and with the ones with "strange" feedback", I'm lost also...

So here's my question:"Is there a method to analyse schematic circuits (or a book)? How do YOU analyse them? Is it like intuitive? Or do you ask the conceptor how it works?"

I'd really like to understand schematic circuits I don't realise myself, because I think it's worthless to build a circuit one cannot undertand.


Thanks for help

JC

 

[Lewish]

5 years of Electrical Engineering at University and 30+ years of experience is a good start.

 

[dpc]

Not knowing what types of circuits you are interested in, I can only say that it does take a bit of experience. As a general rule, I would try to break the schematic down into functional blocks and figure it out one piece at a time - divide and conquer.

But if you are looking at something such as an oscillator circuit, it can be difficult to analyze the first time. Actually, sometimes the person that designed it may not really fully understand why it works sometimes.

Maybe I'm just slow, but I do have a BSEE and 30 years experience and still get stumped quite a bit.

Hang in there.

 

[buzzp]

I agree 100%. There is no substitute for experience! As mentioned, breaking it down into logical parts is the best method assuming you don't have access to the lab book or the engineer that designed it.

 

[Leo01]

Over the years I have found that the ARRL (ham radio operators handbook) is a wealth of information, and can be gotten everywhere. It is a great self teaching guide with actual circuits you can build. Good Luck

 

[ve7brz]

Another vote for experience. And yet another for breaking the circuit down into recognizable sub-circuits. Learn to recognize common component arrangements. Become familiar enough with common circuits that you can say "I remember seeing something like this in this book or that", then look it up.

Study, study, study. Textbooks are good, manufacturers application notes are even better. Others such as the Sams 'Cookbooks' (Prentice Hall) are good. Here's one site where you can find some good books:

http://opamp.com/cf/browse.cfm?Main=ELECTRONICS/COMMUNICATIONS

Good Luck

 

[47gandalf]

In addition to experience, there's another parameter that makes a big difference. That is what used to be called "Drafting". I mean that the schematic can be made easier or harder to understand by the artistic presentation, or design of the schematic.

It's a picture after all. Highly stylized and using a library of custom symbols, but it presents information in a visual format. One picture is worth far more than 1000 words; if its the right picture.

So when I make one, I try to start from a block diagram sketch (either in pencil on an envelope, or maybe in Visio) of the desired overall system.

Then I make the sheets of the schematic "explain" the contents of each box in my block diagram. I use bussing of a collection of signals that compose a logical group (like SPI peripherals, or serial port signals). I use methods that indicate where off page connections go and whether the signal is coming in or going out or bidirectional. And I try to use the format of "inputs on the left of the sheet; outputs on the right" if it makes sense.

In some situations it is easier to understand if I make the schematic resemble the physical board. Like "external sensor connector inputs on the left of thd page; "system outputs to external hardware on the right".

If the program will let me, I like to put dashed-line boxes around some sub-circuits and label them, especially if that label can match one of the boxes in the block diagram.

I try to use an approach much like I use to flow chart code before I actually write it.

I have found over the years that these things help everyone. Because my documents are easier to read, other people are able to successfully understand what I intended to do, and the engineering assumptions and tradeoffs I made. That allows them to modify or extend my work even long after I've gone on to some other place.

And all of this really helps me understand exactly what I'm creating at a level of detail that lets me see conflicts or omissions in time to fix them with an eraser (or mouse) instead of a circuit board re-spin.

 

[nbucska]

Lewish:

Not enough !

<nbucska@pcperipherals.com>

 

[schwarz]

Yes a well drafted schematic diagram makes life easier for everyone designer himself, testing , servicing - all.

Many large organisations follow standards or create their own for docuentation including schematic diagram.If it is one of them you are lucky.

method to analyse schematic circuits - ve7brz has given pretty good advice.

For the big ones I will suggest following steps: even for experienced
1. Read description of the circuit - if available
2. Understand the application requirement radio reciever , motor control etc.
3. Mark the main inputs and main outputs
4. Track main circuit blocks from main i/p to main o/p ignoring safeties, alarms, power supplies,indications etc. Mark with highliter
5.If there are any special ICs read datasheets and application notes
6. Do not get stuck with one functional block. As dpc said figure out one by one .
6. Look at other circuits for same or related application.
7. If the circuit is inside PLD or a microcontroller( I mean software ) - GIVE UP ! unless you have access to the designer.

Have patience, Ask colleagues, friends,Try to work with simple circuits for practice.

To repeat what has already been said several times over. STUDY,STUDY... Experience is the key.

P.S. it's NOT worthless to build a circuit one cannot undertand- building ( & testing )a proven design may help understanding.