How do you start with circuit design? - Page 1
Forum section: electronics / beginners

author: avogadro
author_rank: Contributor
timestamp: March 05, 2019, 10:23:17 pm
content: Hello,I started playing with electronics a couple of years ago. Im in uni currently studying ee and soo far I have only been studying the theory, maths and circuit analysis. I really want to do something practical. I had in mind doing a lab power supply with only discreet elements, so instead of using a voltage regulator Id make one out of discreet elements. Anyway I have started searching the web for any guides in doing that and I have realised that I dont really understand any of it. As soon as there are more than 2-3 transistors involved Im just get confused. Im really stuck with the whole thing. What should I do to get better understanding of it? What books should I read and what else should I do?

author: TimNJ
author_rank: Super Contributor
timestamp: March 05, 2019, 10:38:21 pm
content: Break bigger circuits down into smaller circuits you can understand. Building blocks. You can try "unit-testing" your small blocks, and then piece them together to make the bigger circuit.Mostly, justtry something. I've spent a lot of time wondering about the resources and knowledge I need for a project. And, while you do need some fundamental, foundational knowledge to get you there, I'm arguing that you should just jump into it. Once you encounter the problems, you will learn how to solve them.

author: r3bers
author_rank: Contributor
timestamp: March 05, 2019, 11:33:14 pm
content: Just started playing with existing schemes of arduino, esp, stm32. Modified some uno, blue pill, aithinker boards. Then add relays, logic, opamps, other ic for signals. And so on.

author: rstofer
author_rank: Super Contributor
timestamp: March 06, 2019, 12:21:05 am
content: When you look into PS designs, you will often run into supplies that are completely over the top. Performance may be good but complexity is off the charts and the component count is ridiculous. Mostly, the projects fail to live up to expectations. A big issue seems to be control loops oscillating. I don't know why that is a surprise, I was taught that "Amplifiers oscillate and oscillators don't!".So, start with a simple supply and no expectations. Maybe it works well, maybe it doesn't but at least it can be investigated.https://electronics.stackexchange.com/questions/194435/how-does-this-power-supply-circuit-workDo a Google search for other circuits with 'lab power supply with transistors' or 'regulated power supply with transistors'Here's a site with multiple supplies, at least one is really simple:http://www.repeater-builder.com/pyramid/pyramid-index.htmlhttp://www.repeater-builder.com/pyramid/images/tenna-ps7.jpgI would use a 12.6VCT transformer with the PS-7 Looks pretty easy to understand. It will be easier when you build it up and look at it with a DMM under varying load conditions.

author: Nitrousoxide
author_rank: Regular Contributor
timestamp: March 06, 2019, 02:05:04 am
content: Most complicated systems are made from subsystems. You can learn the subsystems individually and then combine them eventually, some designs may even share similar subsystems.Even for large designs, it is good to replace, or start out with the most simplistic (to implement) solution to get the whole system running correctly, and if you would like to increase the complexity, attack one subsystem at a time.It is good to have a basic arsenal of circuits under your belt, such as (but not limited to):- Amplifiers (Different classes, Summing)- Oscillators- Filters (Active, Passive).- Mixers (slightly more advanced).- Power electronics (H bridge, magnetics) (not really my expertise)It is true, that sometimes solutions have to be generated ad-hoc, but with time and practice comes the ability to intuitively create circuits.Best thing to do is to start a project that you would be passionate about, or something that you would use most days.

author: dave3533
author_rank: Contributor
timestamp: March 06, 2019, 02:28:47 am
content: I'd recommend talking to a professor in your EE department to see if you can get involved in any undergraduate research opportunities. Not only will it give you a relationship within your department, but you can add it to your resume as practical experience once you graduate. You'd be surprised how much cool stuff is going on behind the scenes at university which undergraduates can become involved with. There might be a IEEE student group at your school as well, which might be a good way to meet other EE students and mentors. Also feel free to discuss the troubling circuits with your professors, they'll probably enjoy seeing you take an interest.Also check out The Art of Electronics and/or the student lab manual. The explanations are a little different from what you'd find in a traditional text book which may help you. Finally, Youtube is an absolute wealth of free information and people teaching these types of concepts. Find a Youtuber you enjoy and go wild. The most important thing is to be involved though, you can't just watch or read your way to understanding, you have to crank the equations or try to solve the problems yourself to build up the understanding.

author: vaser888
author_rank: Contributor
timestamp: March 06, 2019, 02:47:06 am
content: Youtube recently recommended me one of Daves old videos which may help you out. He shows and explains an equivalent circuit for the LM317 which will help you.I still gotta watch the other parts to this series of videos but it's really an interesting and informative watch.

author: MrAl
author_rank: Super Contributor
timestamp: March 06, 2019, 03:08:59 pm
content: Quote from: avogadro on March 05, 2019, 10:23:17 pmHi,Transistors have different basic modes of operation so it is good to find out that information. For power supplies they usually operate in the linear mode so you want to study circuits like that. That means as the base current varies the collector current varies and thus the emitter current too.But to show the different ways of looking at a transistor especially in power supplies, the above statement about the base current and collector and emitter currents can be changed. We can also say that as the base emitter voltage changes the collector and emitter currents change.So you see already we have two different ways of looking at the transistor and thus our understanding has to be somewhat flexible because the designer may have had one choice in mind instead of the other.There are other ways too, which start to get more specific as to the connection of the transistor. Take for example an NPN transistor set up as a "voltage follower" circuit. The emitter voltage change (to ground) then approximately follows the change in base (to ground) voltage.So you see there is another way to look at some circuits with transistors.The only way to understand this is to work with single transistor circuits first, a bunch of different types, then go from there. Analyze each one for current and voltage at all nodes and get a feel for what is happening.