How to design electronic circuits

Thread Starter

adam555

Joined Aug 17, 2013
858
The NOT operator is not distributive.

Do a truth table:

A|B|NOT( a or b)|NOT(a) or NOT(b)
F|F|T|T
F|T|F|T
T|F|F|T
T|T|F|F
I think I missunderstood that question. Since he used the 'or' in lower case and the other gates (NOT) in upper case I though 'or' was not a gate, but an option to use a or b for the example.

if he said "NOT(a OR b)" I would have used a NOR gate.
 

MrChips

Joined Oct 2, 2009
30,712
I would be very interested in your help towards an structured approach to circuit design, and to tell you the truth I'm sort of lost at the moment; there's so much available through the internet that I don't know where to start.
Along the lines of what Strantor said, necessity is the mother of invention.

Start with something you need.
How about an oscilloscope? That can be quite a challenge perhaps.
Or a power supply?

A Colpitts oscillator or even a crystal oscillator could be a poor choice for starters.
Without the proper design and components it might fail to oscillate.
 

Brownout

Joined Jan 10, 2012
2,390
I guess you're right. I was trying to say that in a sort of way I find digital quite similar to programming, so in a way it doesn't interests me that much.
I think I might see the problem. You're not interested in digital logic design because it's too 'simple.' Maybe you don't feel sufficiently challenged, so you jump ahead into something more 'complex.' What you might be missing is, before you get all involved in challenging analog electronics, you have to spend alot of time learning "boring" and "simple" things like simple op-amps, simple transistor biasing, simple networks, simple transforms, simple devices, and so forth. Learning is a progression from simple to the not simple. It's not a jump from square 'A' to square 'Z.' Just as you have to study boring digital logic to learn more complex digital logic design (which by the way is not so simple) you also have to study all those boring simple elements of analog electronics before moving on to complex designs. Saying you have no interest in digital electronics because it's 'simple' could possibly be a sigh that you're not really interested in learning electronics, but have just a passing interest.

I'm not the smartest guy on the block, and I've spent most of the last 30 years learning electronics, and I continue to learn. Once I lose my 'interest' I'm done.
 

Thread Starter

adam555

Joined Aug 17, 2013
858
Along the lines of what Strantor said, necessity is the mother of invention.

Start with something you need.
How about an oscilloscope? That can be quite a challenge perhaps.
Or a power supply?

A Colpitts oscillator or even a crystal oscillator could be a poor choice for starters.
Without the proper design and components it might fail to oscillate.
I did a pretty cool power supply in my last attempt at electronics: variable voltage and Amperage up to 30v and 2 Amps, Voltage/Amperage indicator. Even burnt it and fixed it.

I think power supplies are the circuits I best understand; since it was the circuit we were into when my first electronics course ended. Second and third courses I practically learn nothing new...

I would love to make an oscilloscope; but not sure that's even possible for an amateur like me.

I'm planning on doing a distortion for my guitar this week. But I want to start studying those small circuit modules that combine together to make everything else (like the power supply module). Where should I continue?
 

Brownout

Joined Jan 10, 2012
2,390
I want to start studying those small circuit modules that combine together to make everything else (like the power supply module).
That's a good sign.

Where should I continue?
Here's a though: Why not start with one of those electronic laboratories. You build and test all those little blocks, and more importantly, learn what makes them tick. Those labs aren't just for young learners anymore.
 

tindel

Joined Sep 16, 2012
936
Oh, boo freakin' hoo!

I've been a practicing (non-licensed) engineer for 6 years, and in EE type stuff for over a decade. I'm still learning. I shamelessly STEAL other peoples circuits. I make them my own for my requirements, and they usually work. Sometimes it takes me a couple iterations to understand what I didn't think about, but at the end of the day it works.

There's probably 10 scopes on my local Craigslist with better than 20Mhz bandwidth for less than $100. Are they old? Yep! Are they calibrated? Nope! Will you learn something fixing them up? Yep!

Have you thought about FPGA design - it is heavily coding based, but deals with logic gates / flip-flops / etc. The guys I work with command (easily) $100k/year doing that. Some of the really good ones are probably closer to $150k.

To quote one of the great theologans of our time: Try not! Do, or do not. There is no try.
 

#12

Joined Nov 30, 2010
18,224
This reminds me of something I told my ne'er do well nephew. He was, "too smart" to do the math problems in school. He was oblivious to the things he would have learned by doing what seemed like "busy" work. I eventually told him, if you don't practice doing the simple stuff, when you hit a hard one, you don't have the skills you would have learned on the simple ones, and you are stopped.

You want to skip learning a common emitter amplifier stage, then design an op-amp? You are stopped. You want to skip learning all the basic gates and flip-flops, then design a clock? You are stopped.

Pay your dues or you will forever be the guy who can't seem to put three transistors together.
 

Shagas

Joined May 13, 2013
804
By the way , I just remembered :

http://www.talkingelectronics.com/projects/200TrCcts/200TrCcts.html
http://www.talkingelectronics.com/projects/200TrCcts/101-200TrCcts.html
http://www.talkingelectronics.com/projects/100 IC Circuits/1-100_IC-Ccts.html

Open the first link , there are 100 diffrent circuits that you can make with simple components . Find one that you like and built it according to the schematic .
What is the point of that ? You will see. When you build it , you HAVE to analise it!
Take an hour or two to think about how the circuit works (there are descriptions there aswell to help you) , stick your voltmeter and oscilloscope in varius places , notice the values and ask questions. Play around with the values of components , see how that affects circuit functions . Replace components with other ones , see what that does .Also , you can ADD components , see how you can maybe expand the function of the circuit .
After you build at least 20 + of these mini circuits( the more the better) then you will start to intuitively understand how to design them yourself .
Just don't forget : When you build a simple circuit , play around with it and abuse it into oblivion ! Tinkering is what will give you practical knowledge (that applies to everything)
So clean up your breadboard , and get your component boxes together and get to it!!!

The first and second link are transistor circuits ( but there are many other components involved) and the third link is IC circuits.

Trust me that website is a gold mine , it's where I learned alot of my practical 'theory' if that even makes sense.

Also , I post this one alot:

http://www.falstad.com/circuit/e-index.html

Real time simulator . You can see how various circuits work .
 

Thread Starter

adam555

Joined Aug 17, 2013
858
This reminds me of something I told my ne'er do well nephew. He was, "too smart" to do the math problems in school. He was oblivious to the things he would have learned by doing what seemed like "busy" work. I eventually told him, if you don't practice doing the simple stuff, when you hit a hard one, you don't have the skills you would have learned on the simple ones, and you are stopped.

You want to skip learning a common emitter amplifier stage, then design an op-amp? You are stopped. You want to skip learning all the basic gates and flip-flops, then design a clock? You are stopped.

Pay your dues or you will forever be the guy who can't seem to put three transistors together.
It's not about being too clever to learn some things -that's definitely not how I feel with electronics, I actually feel the opposite- it's rather a mixture of laziness and not really knowing what electronics is about.

I think I might see the problem. You're not interested in digital logic design because it's too 'simple.' Maybe you don't feel sufficiently challenged, so you jump ahead into something more 'complex.' What you might be missing is, before you get all involved in challenging analog electronics, you have to spend alot of time learning "boring" and "simple" things like simple op-amps, simple transistor biasing, simple networks, simple transforms, simple devices, and so forth. Learning is a progression from simple to the not simple. It's not a jump from square 'A' to square 'Z.' Just as you have to study boring digital logic to learn more complex digital logic design (which by the way is not so simple) you also have to study all those boring simple elements of analog electronics before moving on to complex designs. Saying you have no interest in digital electronics because it's 'simple' could possibly be a sigh that you're not really interested in learning electronics, but have just a passing interest.

I'm not the smartest guy on the block, and I've spent most of the last 30 years learning electronics, and I continue to learn. Once I lose my 'interest' I'm done.
I thought that since analog came first that's what I needed to try to understand before even touching digital. And since I thought (maybe I'm wrong) that you don't need digital to understand analog and since digital seems simpler to me because it comes easier thanks to programming, I'm not that attracted towards it.

Analog on the other hand for me is a completely alien and fascinating world that really attracts me.

Oh, boo freakin' hoo!

I've been a practicing (non-licensed) engineer for 6 years, and in EE type stuff for over a decade. I'm still learning. I shamelessly STEAL other peoples circuits. I make them my own for my requirements, and they usually work. Sometimes it takes me a couple iterations to understand what I didn't think about, but at the end of the day it works.
I'm not bothered about using other people's designs; it's about not having to look for a circuit every time I need to do something -you need to know its name, how it works, where to find it, how to modify it, etc- a lot of knowledge that I don't have and that I didn't thought was necessary; it's also about the fun and convenience of putting simple circuits together using your own creativity... but as I see electronics doesn't work that way; circuit design is the last step and until you reach that stage you need to use and understand the circuits that have been already designed.

In essence, I wrongly thought that I could avoid one of the main steps in electronics; I thought that because I understood the components and the laws I could simply skip studying the design of basic circuits because I would be able to design them on my own... that I know now, thanks to you all, that it's not going to happen, and that there's no way around it.

There's probably 10 scopes on my local Craigslist with better than 20Mhz bandwidth for less than $100. Are they old? Yep! Are they calibrated? Nope! Will you learn something fixing them up? Yep!
I guess I need to be on the look for a cheap one; if I want to continue with electronics. At the stage I am now it's starting to be a must, and in a way I'm stock because I don't have one.

By the way , I just remembered :

http://www.talkingelectronics.com/projects/200TrCcts/200TrCcts.html
http://www.talkingelectronics.com/projects/200TrCcts/101-200TrCcts.html
http://www.talkingelectronics.com/projects/100%20IC%20Circuits/1-100_IC-Ccts.html

Open the first link , there are 100 diffrent circuits that you can make with simple components . Find one that you like and built it according to the schematic .
What is the point of that ? You will see. When you build it , you HAVE to analise it!
Take an hour or two to think about how the circuit works (there are descriptions there aswell to help you) , stick your voltmeter and oscilloscope in varius places , notice the values and ask questions. Play around with the values of components , see how that affects circuit functions . Replace components with other ones , see what that does .Also , you can ADD components , see how you can maybe expand the function of the circuit .
After you build at least 20 + of these mini circuits( the more the better) then you will start to intuitively understand how to design them yourself .
Just don't forget : When you build a simple circuit , play around with it and abuse it into oblivion ! Tinkering is what will give you practical knowledge (that applies to everything)
So clean up your breadboard , and get your component boxes together and get to it!!!

The first and second link are transistor circuits ( but there are many other components involved) and the third link is IC circuits.

Trust me that website is a gold mine , it's where I learned alot of my practical 'theory' if that even makes sense.
Thanks. I began already studying those circuits from talkingelectronics last week. But I mainly do them in simulations because I don't have an oscilloscope.

You know, this time is a bit easier than the previous ones thanks to the internet; you have all this websites with circuits and theory, videos, ebooks, and even people to talk with. I didn't have any of that in my last try 10 years ago.

Also , I post this one alot:

http://www.falstad.com/circuit/e-index.html

Real time simulator . You can see how various circuits work .
That's perfect. Most of the times I have problems understanding the explanations of the circuits I'm studying, this is the perfect complement.

Thanks a lot. :)
 
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Shagas

Joined May 13, 2013
804
But I mainly do them in simulations because I don't have an oscilloscope.
Well now it's the time to start thinking about getting an oscilloscope and a good DMM .
You can't substitue simulation with actuall hand-on work . That's where your problem is.
You can't spend 5 years learning professional statue sculpting theory and then expect to immerge a master sculptor .


This is how I do it :
I learn a snippet of theory , and I IMMEDIATELY apply it to practice . If I don't , then I'll
a)Forget it
b)Lose interest to learn further theory in that particular chapter


As for using other peoples circuits :

Imagine you are building a house . Every time you are going to build a house you aren't going to reinvent the brick are you ? You aren't going to reinvent concrete . You are going to use the ready products to build the house .
Now you might learn how to make bricks and how bricks work ( you should!!!) and make them at least once . But it's a one or two time thing . Once you have made it then you can go on using already made products to make something bigger . It's the basic principle of progress. When you are building that house you aren't going to be considering how bricks are made , BUT you might want to consider their characteristics like stregth etc , that's why you should to some level know how they are made and how they work .

Now bringing that analogy to electronics :
You might be building an audio amplifier out of discrete transistors and components . Now lets say that somewhere in that amplifier you will need a current source . You will not re-invent the current source , but you can use a ready schematic for it (you have to know how it works though so you can manipulate it , that's why you build it at least once or twice ) . Now lets say you are building an alarm system which generates a loud wail when triggered. You aren't going to re-invent the audio amplifier , you will just use an amplifier integrated circuit and probably an integrated tone generator and buzzer because your main project and concern is now the alarm system and not those discrete components .

I hope you are starting to see the picture
 

Thread Starter

adam555

Joined Aug 17, 2013
858
When you design electronic circuits you rarely create something new that no one has ever done before. You can bet that 99% of the time you are going to use a circuit that someone has used before.
As for using other peoples circuits :

Imagine you are building a house . Every time you are going to build a house you aren't going to reinvent the brick are you ? You aren't going to reinvent concrete . You are going to use the ready products to build the house .
Now you might learn how to make bricks and how bricks work ( you should!!!) and make them at least once . But it's a one or two time thing . Once you have made it then you can go on using already made products to make something bigger . It's the basic principle of progress. When you are building that house you aren't going to be considering how bricks are made , BUT you might want to consider their characteristics like stregth etc , that's why you should to some level know how they are made and how they work .

Now bringing that analogy to electronics :
You might be building an audio amplifier out of discrete transistors and components . Now lets say that somewhere in that amplifier you will need a current source . You will not re-invent the current source , but you can use a ready schematic for it (you have to know how it works though so you can manipulate it , that's why you build it at least once or twice ) . Now lets say you are building an alarm system which generates a loud wail when triggered. You aren't going to re-invent the audio amplifier , you will just use an amplifier integrated circuit and probably an integrated tone generator and buzzer because your main project and concern is now the alarm system and not those discrete components .

I hope you are starting to see the picture
Yes, I understand that now; but I didn't when I began this thread. At the beginning I thought that with a little bit of practice you wouldn't need to know a circuit before hand to implement it in your projects, I thought you just came up with circuits all the time without the need to study them previously.

For example: Yesterday I built a simple distortion for my guitar, but the schematic was only the distortion without amp. I wanted to attach a small speaker to it, and knew that you can do simple amplifiers with transistors, so I looked at how those circuits work and implemented a simple amplifier to the output of the distortion. I would had never done that before; I would had simply tried to break my head trying to figure out on my own how to increase the output of the distortion.

Well now it's the time to start thinking about getting an oscilloscope and a good DMM .
You can't substitue simulation with actuall hand-on work . That's where your problem is.
You can't spend 5 years learning professional statue sculpting theory and then expect to immerge a master sculptor .

This is how I do it :
I learn a snippet of theory , and I IMMEDIATELY apply it to practice . If I don't , then I'll
a)Forget it
b)Lose interest to learn further theory in that particular chapter
I've been looking for one for a while, but so far I find them too expensive; even second hand ones. I was also thinking on buying one of those that you connect to the PC, but I'm a bit scared of the idea of blowing up both in a beginners mistake.

The other thing that's stopping me from building most projects is not having all the components. I try to buy new components regularly, but every project requires new stuff, and the shop is a bit far away. Lately I even began to salvage stuff from old electronic equipment; I gathered quite a lot of that years ago but it all ended in the bin.
 

Shagas

Joined May 13, 2013
804
You can get a handheld oscilloscope like this for less than 100 bucks:
http://www.vellemanusa.com/products/view/?country=us&lang=enu&id=525377
Easy to use , and doesn't take up space .
It's no professional tool and has its downsides but it's more than enough for you right now for the next year or two . Then you can start to look into something more serious .
The pc oscilloscopes are also a cheap alternative.

Salvaging components is pretty usefull . If i'm building something then I get pissed if I don't have a specific component that I plan ahead :D
 

Thread Starter

adam555

Joined Aug 17, 2013
858
You can get a handheld oscilloscope like this for less than 100 bucks:
http://www.vellemanusa.com/products/view/?country=us&lang=enu&id=525377
Easy to use , and doesn't take up space .
It's no professional tool and has its downsides but it's more than enough for you right now for the next year or two . Then you can start to look into something more serious .
The pc oscilloscopes are also a cheap alternative.

Salvaging components is pretty usefull . If i'm building something then I get pissed if I don't have a specific component that I plan ahead :D
Yes, I was going to ask about those. I looked at various handheld oscilloscopes for $50 to $100; but I'm not sure what exactly what specs should I look for (e.g. how to compare which one is best).

I also found this one: DIY Pocket-Sized Oscilloscope Kit For $US33



It also comes in a kit for just $33 that you put together at home, and I don't really see much difference between this one and the other handheld.

What do you think?
 

Shagas

Joined May 13, 2013
804
Hey I'm not expert . I only own that crappy handheld one , but it does the job and is effective and portable etc.
It's up to you .
33bucks is a pretty good price , you might want to check out what kind of components it has . I'm guessing there is going to be some SMD there so if you are comfortable with that then you can try it out!

Some more experienced members are probably going to shoot down that kit that you linked due to lack of reliability etc but it's up to you :)

I think if you are a beginner and don't want to spend alot of money then the specs aren't important for now. Just get one , use it for 6 months/year and then you can start thinking about something more serious
 

BobTPH

Joined Jun 5, 2013
8,813
I would look for a used analog scope. I just recently sold my 20MHz dual-trace one for $40. Way more capable than the $33 one you linked to.

Bob
 

Veracohr

Joined Jan 3, 2011
772
You say you understand the basics, and how all the components work, but I wonder how deep that understanding goes.

Take a sine-wave oscillator for example, as you attempted to build.

- Do you understand the conditions necessary for a circuit to oscillate - the Barkhausen Criterion?
- Do you understand how a Colpitts oscillator, Wien-bridge oscillator, Twin-T oscillator and phase shift oscillator all produce sine wave outputs even though they all have different configurations?
- Do you understand how real (imperfect) components affect the ideal circuit response?

Once you truly understand all these things, maybe then you can try coming up with a completely novel approach to the same end.

Maybe also you should consider this: is it more important to you to come up with a completely original circuit, or is it more important to you to produce something that works as you want?
 

Thread Starter

adam555

Joined Aug 17, 2013
858
I would look for a used analog scope. I just recently sold my 20MHz dual-trace one for $40. Way more capable than the $33 one you linked to.

Bob
I would had bought it for $40. :)

You say you understand the basics, and how all the components work, but I wonder how deep that understanding goes.

Take a sine-wave oscillator for example, as you attempted to build.

- Do you understand the conditions necessary for a circuit to oscillate - the Barkhausen Criterion?
- Do you understand how a Colpitts oscillator, Wien-bridge oscillator, Twin-T oscillator and phase shift oscillator all produce sine wave outputs even though they all have different configurations?
- Do you understand how real (imperfect) components affect the ideal circuit response?

Once you truly understand all these things, maybe then you can try coming up with a completely novel approach to the same end.

Maybe also you should consider this: is it more important to you to come up with a completely original circuit, or is it more important to you to produce something that works as you want?
I understand what individual components do and the basic laws; but not how they behave inside particular circuits. Now that I know that the basic components also includes fundamental circuits (e.g. oscillators, amplifiers, etc.) I recon that there's were I should focus my efforts.

I'm not bother about coming up with original circuits; I wrongly thought that by knowing the individual components everyone was able to create circuits, so I felt frustrated for not being able to do it. Now I know, thanks to the answers on this thread, that studying and understanding basic circuits is a fundamental part of electronics.
 
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