How to design electronic circuits

Thread Starter

adam555

Joined Aug 17, 2013
858
The only thing I can add to the good comments and advice you've gotten thus far is - recognize the fact that you'll learn a LOT more from your failures than from your successes. If you design something and it fails, don't abandon it, dig in and learn WHY it failed and how to fix it. I think *every* design engineer will agree that the most valuable lessons have been learned as a result of failure, not success.
I'm going to put an example of how frustrated I am at the moment, and why.

I began 2 test projects today, both have to do with the Colpitts oscillator; which I need to make a metal detector. Built one for the metal detector, and also to test if I can emit radio signals. Built them, don't work, don't do anything, and I don't even have an oscilloscope because it's too expensive for a amateur like me... how can I advance from there; when I can't even tell what's going wrong?
 

shortbus

Joined Sep 30, 2009
10,045
Or do what I do... After the smoke clears and the sparks stop, tell anyone looking "boy that worked just the way I planed it". :)
 

strantor

Joined Oct 3, 2010
6,782
That means more than just the internet culture follows the 89-10-1 rule or 90-9-1 rule.
Had to google that. When I was referring to the 1%, I was actually thinking within my own world, which includes the regular members of the forum. So I when I said 1% I probably should have said something smaller, like .01%. But all this is pulled straight out my hind end. I have no idea what percentage of people have actually created something that did not exist before. I suspect it is very, very small.

I've never done it. I have cobbled purpose-built things together that can't be bought, but they were made from off the shelf stuff, that anybody with similar need could have constructed. Nothing revolutionary or pioneering; for example, like the transistor. Whoever invented that, invented something that had never been seen before. Whoever was the first to put 4 transistors together to make an H-bridge, just cobbled together someone else's work; it was new, but not revolutionary or pioneering in my opinion, because anybody with similar need could have constructed it.
 

WBahn

Joined Mar 31, 2012
29,976
I wish I got a spark or smoke once in a while... my failed circuits do absolutely nothing!!!
In that case, announce just before you flip the switch, "Okay, if this goes as expected, this should do absolutely nothing. Let's see...."

Notice the slight difference between "as expected" and "as intended" or "as designed". :D
 

Thread Starter

adam555

Joined Aug 17, 2013
858
So, where are the results of my digital test... did I pass? :)

You may actually be able to design more than you think. You might just need a structured approach to design, and we might be able to help.
I found two websites with tutorials that I'm planning on checking out; apart from this one:

http://www.electronics-tutorials.ws/index.html
http://www.talkingelectronics.com/pay/TEI-Index-Full.html

Any suggestions on how to proceed, without going again through all the formulas, laws and components for the Nth time?

By the way... what's the cheapest option for an oscilloscope?
 
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LDC3

Joined Apr 27, 2013
924
Not sure exactly what you're asking for...

1) is just an AND gate
2) an OR gate
3) an NOT gate

and

4) a NOT gate for b and both into an AND gate, or a NOT gate for a and both into an AND gate.

But that's easy, that's just digital...
Sorry, but 3 is a NOR gate, not a NOT gate since a NOT gate only has one input.
For 4, it is a XOR gate followed by a NOT gate, or a NXOR gate.
 

LDC3

Joined Apr 27, 2013
924
I'm going to put an example of how frustrated I am at the moment, and why.

I began 2 test projects today, both have to do with the Colpitts oscillator; which I need to make a metal detector. Built one for the metal detector, and also to test if I can emit radio signals. Built them, don't work, don't do anything, and I don't even have an oscilloscope because it's too expensive for a amateur like me... how can I advance from there; when I can't even tell what's going wrong?
You can use a Windows program called WinScope that uses the audio input for an oscilloscope. It limits the AC frequencies to below 20 kHz. Someone also mentioned that the input is capacitor coupled, so a DC signal will not go through.
 

WBahn

Joined Mar 31, 2012
29,976
By the way... what's the cheapest option for an oscilloscope?
You can download an oscilloscope and/or function generator for free that uses your sound card as an I/O device.

You can get USB oscilloscopes for under $100 or so.

It all depends on what your needs are. The less performance needed, the lower the cost.
 

Thread Starter

adam555

Joined Aug 17, 2013
858
Sorry, but 3 is a NOR gate, not a NOT gate since a NOT gate only has one input.
For 4, it is a XOR gate followed by a NOT gate, or a NXOR gate.
Well, he said "NOT (a or b)", so a single NOT 'a' or NOT 'b' gate would do.

And for 4, this is what I meant; which I guess gives the exact result asked:



or "NOT"? :confused:
 

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Thread Starter

adam555

Joined Aug 17, 2013
858
You can use a Windows program called WinScope that uses the audio input for an oscilloscope. It limits the AC frequencies to below 20 kHz. Someone also mentioned that the input is capacitor coupled, so a DC signal will not go through.
You can download an oscilloscope and/or function generator for free that uses your sound card as an I/O device.
That's ideal!!!

Thanks
 

Brownout

Joined Jan 10, 2012
2,390
Not sure exactly what you're asking for...

4) a NOT gate for b and both into an AND gate, or a NOT gate for a and both into an AND gate.
So, you just designed the "exclusive or" gate. You said you couldn't design anything.

But that's easy, that's just digital...
In your first post, you said you couldn't design a digital circuit ( a flip-flop ) Now digital is easy. That's alot of progress in a few short minutes.... Fact is, you can probably do more than you think you can.

However, if you think you're gonna design good stable oscillators without studying existing oscillator design, what makes good ones and what makes poor ones, you're just expecting too much.
 

WBahn

Joined Mar 31, 2012
29,976
Not sure exactly what you're asking for...

1) is just an AND gate
2) an OR gate
3) an NOT gate

and

4) a NOT gate for b and both into an AND gate, or a NOT gate for a and both into an AND gate.

But that's easy, that's just digital...
(3) is a NOR gate -- perhaps that was just a typo.

But the point, I think, is can you design the CIRCUITS to actually implement this?


In order to "design something new" (whatever you decide that "new" means), you need a lot of tools in your toolbox, which is primarily the knowledge of how lots of things work and HOW they accomplish the things they do. The is much more than just knowing about a bunch of stock modules that can be thrown together to do something that no else has ever done, but also being able to look at a problem and consider how something that is only vaguely related goes about doing something that is similar enough that you can leverage that knowledge.

When I had to design asynchronous logic for a clockless event-driven circuit on an IC that had to run with delays measured in small fractions of a nanosecond, I used as my inspiration the way that mechanical sequencing was performed by the hydraulic systems on the F-15s that I had worked on twenty years earlier as just a maintenance technician. As a maintainer, I didn't NEED to know how they worked -- the tech orders gave step-by-step troubleshooting and repair instructions. But I have always loved to learn about anything and everything -- so I dug into manuals and documents to understand the concepts behind how they worked. Who would have thought that those same ideas would end up being used on a cutting-edge lidar chip decades later?
 

Thread Starter

adam555

Joined Aug 17, 2013
858
So, you just designed the "exclusive or" gate. You said you couldn't design anything.

In your first post, you said you couldn't design a digital circuit ( a flip-flop ) Now digital is easy. That's alot of progress in a few short minutes.... Fact is, you can probably do more than you think you can.

However, if you think you're gonna design good stable oscillators without studying existing oscillator design, what makes good ones and what makes poor ones, you're just expecting too much.
Well, the way I see it is what WBahn asked...

But the point, I think, is can you design the CIRCUITS to actually implement this?
I can put two gates together, but I'm not sure I can put together the whole circuit. What I mean is, once you have the environment ready to use digital components, then it seems fairly easy; the difficult part is making the inner workings of the digital components, like the flip-flop.

If I had to do the whole circuit I would do something like this for number 4)



But anyway, I also know this stuff from programming (the logical gates); so it's kind of cheating.
 

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Thread Starter

adam555

Joined Aug 17, 2013
858
Got Winscope, but I'm afraid to use it. I don't have enough confidence to know exactly what I can measure and what I cannot measure. One mistake and I'm left without oscilloscope and computer. :(
 

Brownout

Joined Jan 10, 2012
2,390
But anyway, I also know this stuff from programming (the logical gates); so it's kind of cheating.
Oh heck no. The secret to good design it to cheat every change you get. In other words, if you can relate learning to something you already know, don't fight it. Some people spend their lifetime and not understand it.

I'll bet you looked at alot of example code before you ever wrote a useful program. I'll bet you didn't invent the "for loop" all by yourself!
 

MrChips

Joined Oct 2, 2009
30,708
First of all, a J-K flip-flop is a pretty complicated thing to design, and whatever genius first invented it surley studied other latching designs before coming up with it. So in essence, the flip-flop was developed over time by people who studied other people's work. That's how one learns to design and invent. Dont' beat yourself up just because you didn't invent something out of thin air.

You may actually be able to design more than you think. You might just need a structured approach to design, and we might be able to help.
Read this one over again.


Dont' beat yourself up just because you didn't invent something out of thin air.

You may actually be able to design more than you think. You might just need a structured approach to design, and we might be able to help.
 

Thread Starter

adam555

Joined Aug 17, 2013
858
Oh heck no. The secret to good design it to cheat every change you get. In other words, if you can relate learning to something you already know, don't fight it. Some people spend their lifetime and not understand it.

I'll bet you looked at alot of example code before you ever wrote a useful program. I'll bet you didn't invent the "for loop" all by yourself!
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 also bought an arduino a few months ago, but I barely used it because I also find it too easy; specially since I can do it almost all with the software. I like analog; that's the difficult stuff. :)

The difference with programming is that I barely needed to look at other people's work; it sort of came natural by reading the reference guides for languages. It's also true that I began very young, but I don't think I ever got stuck with any of the arts or sciences that I learnt along my life as with electronics... it's the only thing so far that completely beats me.
 

Thread Starter

adam555

Joined Aug 17, 2013
858
Read this one over again.
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.
 

WBahn

Joined Mar 31, 2012
29,976
Well, he said "NOT (a or b)", so a single NOT 'a' or NOT 'b' gate would do.

And for 4, this is what I meant; which I guess gives the exact result asked:



or "NOT"? :confused:
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
 
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