What do you do when you look at a schematic ?

[RivaultUser]

Hey guys, I've been struggling in electronic for about almost 1 year ( yeah, I'm still a newbie who needs a lot experience )

What makes me want to post this question is

Do you guys really able to read a SCHEMATIC ?

What I'm talking about is not such a simple schematic, but a schematic in a different level ( yes, you know what I mean )

A schematic that includes lots of components, lots of combination between components, lots of connection between components

Now what I really wanna know is :

Do you really can read that kind of schematic ?

I mean, do you really can explain how this schematic works? By explains it one by one, what each component does in that circuit ?

Cause I feel that it's wayyy too hard to do all that ( recently I just learn about bypass capacitor, now that I know why circuits usually uses capacitor )



So, You really can do it?

[benemorius]

Yes, in time you'll see that it works much like written language. By that I mean you'll end up recognizing groups of components and functional blocks and no longer have to study each and every component and connection, just like you don't actually look at each letter in a word in order to determine what word it is. Adding words to your vocabulary happens with experience, so for the most part it will just take some time.

In the mean time, take that really big schematic and cut out the part you're interested in looking at and you'll find that you're left with a simple small schematic to study. Just ignore the bits you can't figure out. Repeat until you've digested the whole thing.

[madires]

Yes, in time you'll see that it works much like written language. By that I mean you'll end up recognizing groups of components and functional blocks and no longer have to study each and every component and connection, just like you don't actually look at each letter in a word in order to determine what word it is. Adding words to your vocabulary happens with experience, so for the most part it will just take some time.

And it's very helpful to own a nice dictionary to look up all the unknown words :-)

[Shuggsy]

Gah, two people beat me to it! It is like learning a different language.

One way to learn a language is from the ground up. That is, first you learn the basic syllables and letters, then you move on to combinations of the syllables and letters to make words, then you use combinations of the words to make sentences. All of these work together to convey the idea or concept you're trying to get across. Another way to learn a language is by simply learning common letters, words, and phrases. Once you understand the really common parts, you can use those as a base and begin learning the non-so-common aspects of the language. Eventually, with either approach you're able to look at and understand whatever you are reading or speaking about even if you sometimes have to refer back to a dictionary or ask someone what something means.

Now, with electronics, there are some similar approaches. In the first example, you learn the basic components and equations [resistors, inductors, capacitors, and Ohm's Law for example], then you move on to circuits [RC filters, basic op-amp circuits, etc.], then you learn how to combine those basic circuits to perform some function [power supply, controllable oscillators, signal conversion, and the list goes on]. In the second example, you learn by viewing common circuits [many op-amp circuits, simple resistor dividers, transistor switching, etc.] and understanding their function then use that as a base for other circuits you might encounter [what's different between the circuit you're looking at and one that you know?] and by studying these you can eventually lead to a full understanding what the components within circuits are doing. If you get stumped somewhere, there are people out there [here, for example!] that can help you understand.

In the end, whether you're reading a book or reading a schematic, if you understand the language then you can understand the concept [or function] trying to be presented. You ask about knowing component by component what everything does in a circuit. By and large, that's true, but sometimes the circuit is complex or odd enough that it takes more in-depth study to determine what exactly something is doing. At least, I'm not at the level of being able to explain every component in every circuit yet...   

[free_electron]

sure. schematics afre perfectly readable. provided they are drawn logically uinsg wires andare not just a collection of parts with etnames on their pins (like all the tripe you find on the internet these days )

Grab a schematic form Hewlett packard service manual or tektronix manual. those are drawn the way it's supposed to be drawn. A correctly drawn schematic is easy to follow and has all the information you need. Lots of older schematics for TV's would have little balloons showing voltages and waveforms for certain nodes and would use colored lines or differently shaded lines to indicate the signal path.

[Smokey]

I've actually heard this question a lot from my non technical friends.  I get the "you understand all that"?  Followed by a bunch of "whats this do"s

[JoannaK]

Well, shematic is a bit like mathemathical expessions, both need experience and knowledge. Also both of them can be quite terse and hard to read is one is not fluent with the all the symbols involved. Also a lot depends on if I'm supposed just to make it happen (layout/routing) or if I'd supposed to understand the inner workings fully (debug/revision). Sometimes you think you understand the design, but surprices do happen. It's also quite easy to misread some part or block especially if one is tired or hurry.

[PA0PBZ]

Nobody knows what each single component does by just having a brief look at a schematic, and there is no need to do that, like there is no need for you to read a whole book, or a paragraph or even a page by just having a brief look at it. Most of the time you know what the schematic is about so go from there, and try to divide it in functional groups.
Let's take for example a schematic of a power supply. We assume it is a power supply because someone said it is, so without any further information let's say it is. So the schematic as a whole is a power supply, now let's try to divide it in smaller groups.
A basic power supply should at least have an input and an output, and it should not be too difficult to find these in the schematic. The input might have a transformer, a rectifier and some capacitors, and would normally be at the left side of the diagram, so mark that as the input. You can expect the output to be at the right side of the diagram, and probably also has one or more capacitors and an output connector, so mark that as the output.  What is in between depends on the type of power supply, mostly there is some kind of regulation (linear/switching), maybe it is adjustable, it could have some kind of over current protection or if it is a bench supply there could be voltage and current indicators, either LCD, LED or even plain old needle meters. It is not too hard to divide that middle part in regulation, control, display and so on.
Now it depends on why you are looking at this schematic. Are you trying to fix it, do you want to build something similar or are you just interested in the working? Concentrate on the part that needs more attention, if it does not regulate the problem is most certainly not in the input. If there are any integrated circuits in there find the data sheets and look at the reference designs, it will tell you a lot about the (sub)circuit and why certain components are there and what their values should be.
A few books could probably be written about this subject and I'm not going to do it tonight, just remember:
- you don't have to understand everything
- divide it into functional blocks
- concentrate on the block(s) you need to understand

[Arrow]

I say, begin at looking at the power lines, try to identify the power supply in the schematic, and all the different voltages, check in the circuit if there are known schematic blocks like voltage regulators, comparators op amp, or voltage dividers and so on. After a while you will get used to the schematic. 

[Alana]

I learned how to read schematics by reading schoolbooks from my parent's time on car electronics and later electronic hobby magazines. Both had trought description of "how stuff works" written in more or less common laungage.
This gives lots of inside into how it works based on schematics and drawings, and gives this intuitive aproach that you try to foool around with how current/signal goes trought device. In my opinion best way to do it.

[tinhead]

I've learned to draw them, as "free_electron" said, logically. Therefore no problem to read them. However, at some point it make sense
to use netnames instead of wires. Example, in this one i draw:

https://www.eevblog.com/forum/chat/hantek-tekway-dso-hack-get-200mhz-bw-for-free/?action=dlattach;attach=12233

the input stage, trigger, sample/hold, and PSU pages are easy readable, you can easy follow the signal flow.
the front panel was having only few components, but lot of them cross juncted, so i decided to switch back to netnames.
FPGA, SoC and memory part was anyway to complex/split in wrong block sizes to make it easy readable on one sheet.

I don't like "netnames only based" schematics, it is sometimes hard to follow (oh well, not in Altium but in cutted pdf version). I'm trying at least to create an overview page to have later a clue what/how belongs together. But even with an overview page it is sometimes pain in the ass by first look of it, example (however, here is nothign special to read)

https://www.eevblog.com/forum/chat/cheap-virtex-5-board-(actually-it-is-primesense-devkit-better-known-as-kinect)/?action=dlattach;attach=36373

Cause I feel that it's wayyy too hard to do all that ( recently I just learn about bypass capacitor, now that I know why circuits usually uses capacitor )

don't worry, after 30 yrs of electronic hobby/school/work i have still sometimes to look twice to see something obvious on the schematic.

[PA4TIM]

After about 4 years I was able to split schematics up in blocks I could understand, after 5 years I knew for 90% what every component did in a schematic and was able to design some things.
Now I know for 95% and can make a educated guess about the last 5 % ( i'm talking pure analog stuff, i have no clue about digital, to complex for me)
I know enough about all components but sometimes desingers use need tricks you not see right away.

but at first you must recognize things input, output and blocks in between like an amplifier, then recognize within those blocks like currentsources, switching parts, oscillators, basic opamp configurations, understand feedback ect.

So you see an opamp, first step is to recognize it as a inegrator, or non inverting amplifier, or diff amp ect. Second step is you know why they use the values of components, calculate things like gain, why some components are added ect. Next step is you can design one and the ultimate is you can do things like laplace transformations and bode plots to calculate your phase margin ect.

For components, first you know what an ideal capacitor does, then you learn about the major types, then about the paracitics, then you learn to see problems with that or use them in your advance. Know all the sort of caps, what their strong and weak points are, things like voltage cooficients, ESR, ESL, dielectric absorbtion, self resonance, type of dielectrium, tempco, leakage ect.

And this also for resistors, inductors, transistors and fets, opamps, diodes, fuses, switches, zeners, voltage regulators, crystals, VDRs, PTCs, NTCs, varistors ect ect

And when you know all these things, designing becomes more and more easy.
But long before that you will need to understand schematics.

But wat is a simple schematic for someone as experienced in design like free electron can still be very hard to understand by me. I have for instance no troubles with the schematics from an analog oscilloscope or multimeter.

It is indeed like reading, first a cartoon without text, then ou learn letters, then words, then a cartoon with text, then a kids reading book, then things like simple storyd upto literature andend things like complex study books.

[blackdog]

Hi PA4TIM

Nice explanation.

I would like to see my clients be aware of the difficulty that a technician
must do to gain all the knowledge for his profession.

Most of the time a boy or a girl singing in a stupid program gets more credits...

Back on topic, if you realy want to be a electronics man, a minimum of 5 years before
a single look tels you what the basics ar of a complicated schematic.

I always look first @ the powersupply, how manny rails en voltages.
Is the schematic linear (left to  right).
Try to find the logic of the guy who draw it.
I can tell you, at least 75% is a mess...

You also learn like what Free_Electron says, to recognize how HP and Tektronix draw there schematics.

Look @ this schematic, its linear.
PA4TIM, Free_Electron wil see in a few seconds if there is a big mistake...
It is ease to read (i  hope so) 



Kind regarts,
Blackdog

[codeboy2k]

oh Bram.. nice to see you finally redrew it without the LM10 and using a better reference and opamp  now. 

[jancumps]

Following the diagram with an oscilloscope also helps - if you have the actual unit in front of you. Try to understand the flow of the schematic, and measure it.
Amplifiers are easy examples, because the signal follows a path from start to end.  They have common transistor and filter patterns in them that can be measured with even the most cheap scope: voltages are safe, frequencies are low, and you can use your computer's sound card to generate input signals.
See how the input signal is amplified, what the tone settings do to the signal, what happens if input frequency changes, and what happens in the output stage.
The additional visual aspect - and the fact that you are finding back the actual components from the schematic on the pcb - can help you to find the flow in your first diagrams.

[minibutmany]

You will probably find (assuming you study both digital and analog circuits) that analog circuits are a little harder to completely understand. Digital electronics will always have easily defined functions and if you can think logically you will understand every circuit you look at. With analog circuits there are many more factors that go into making something work. Its a little bit more like studying living things because there is always some disease you haven't seen and maybe not a known cure! One thing with analog electronics is that you will always be able to identify every component on the page, it really comes down to different characteristics applied to the same parts. New digital IC's are coming out daily and its impossible to recognize them all. Just keep in mind that you still need a basic knowledge of analog circuitry to understand digital circuits because essentially the IC's you are working with contain a whole bunch of parts found in analog circuits.