Making a Circuit from a Schematic -- The Learning Circuit 34

Thank you thank you so much! You helped me a lot sir! Self learning is really hard without a road to follow. I'm actually a second year engineering student but in a different field. I just got interested with electronics and started digging information and applications. Would love to build something in the future.  Thank you so much!

Hi Justine,

You have an excellent question. As far as a beginning point on electronics I will refer you to a discussion that I started five years ago as this question has been asked several times.

https://www.element14.com/community/people/jw0752/blog/2015/11/04/i-want-to-do-electronics-where-do-i-start

Your question about the different bipolar transistors is an example of the human mind needing to fill all the possibilities with a part number. I suspect that with a little rigging six different transistors could probably cover 95% of all applications. Instead we have thousands of slightly different transistors all with their own unique number. Then we have the different manufactures who may or may not use the same number for a nearly identical transistor. So we end up with thousands of numbers and no one I know begins to understand how to differentiate most of them. The other thing to keep in mind is that even transistors of the same number from the same manufacturer do not come off the assembly line identical. They are each quite unique.

The book I suggested will help you understand transistors in general and then you have to understand the concepts of Voltage, Current, and Power so that you can choose an transistor that fit your application. For example if you have an application where you are going to be working with 24 volts and your load will be drawing 2 Amps then we know that there will be 2 Amps times 24 Volts or 48 Watts of power being used. For this application we would need a transistor that can tolerate voltage as high as 24 volts and a current of 2 Amps. It would have to be a transistor that we could tie to a heat sink as it may get to hot to properly dissipate all the heat on its own.

As you gain knowledge about the general characteristics of the different components you will be able to see how they fit together and why there is need in many cases for a variety of different properties. If all you want to do is turn a 5 Volt light on and off then you can probably use just about any transistor that is available. If instead you want to turn something on and off very quickly or drive a load that takes more power then you may need a more specialized transistor.

Engineers go to school for 4 or more years to learn what is needed for the basics of electronics. People like me, who have not had a formal education in electronics and instead have spent the last 60 years playing, experimenting, and repairing electronics bring experience to the table. For the last 10 years since I retired I have been learning from the engineers on this site and slowly filling in some of the cracks between my experience with the theory and actual electronics knowledge. Some days when the guys get to discussing things in depth I feel like a second grader looking into the advance calculus class. I don't understand all that is being discussed but I read and absorb what I can and I can ask questions which are always handled with courtesy on this site. This site allows me to appreciate the immense field of electronics.

If you enjoy learning, fixing and building things you should really enjoy electronics. It is a process and there is never an end to what there is to learn.

The book I suggested is only one path so if you find another that works better for you go for it.

I know I didn't answer your question totally but hopefully this is a start.

John

Good day John!

Wanna ask a question if you have something to recommend like a book that would actually explain how each electronic component works. I'm just really confused how each components works in different use. Like why we have different type of bipolar transistors? the codes of each components is what I don't understand. Thanks!

Because my basic skills were becoming rusty - I don't use it a lot, but feel that these are essential things you shouldn't lose - I refreshed by taking Georgia Institute of Technology's Linear Circuits course a few years ago.

It helped . Quite intensive.

shabaz  wrote:

 

Agree with all that!

I should have read it before I subsequently posted.. my response to the question was also very similar.

As if we had the same teacher. That's how similar it is.

Agree with all that!

I should have read it before I subsequently posted.. my response to the question was also very similar.

Cant find a single lesson all over the internet where it explains what happens to voltage and current, step-by step, though a circuit like the one in this lesson

That circuit (if it's the one I saw briefly in the video) has about 20 nodes, each with current passing through, and different voltages between the nodes... that's 40 measurements right there, for a static (unchanging) scenario. As the circuit is powering up, and as it is doing what it is intended to do, those values will change.. so another 40, 80, 120, 160 or so measurements, depending on how many states you're interested in examining.

You can see the voltage and current at any desired location by using a simulator. But, look at this simple four-component circuit:

https://www.falstad.com/circuit/

Could you make head or tail of what is going on, despite having the voltage and current information visible right there? The answer shows why your proposed method of learning won't work.

The answer is no - it requires learning about what each component does and learning some circuit theory and typical observed patterns or networks of components. There's no substitute for picking up a textbook and studying, and experimenting, in conjunction with the 'Learning Circuit' video series (which is really excellent). After that, you'll start noticing that the larger circuits can in places be split into commonly-observed patterns of components, many of which can be designed in some isolation occasionally.

cavenagy  wrote:

 

....

You cant expect somebody to use simple theory and then put it in practice on a complex real scenario.

Cant find a single lesson all over the internet where it explains what happens to voltage and current, step-by step, though a circuit like the one in this lesson.

Thanks.

That's part of what I learned during electronic studies:

Circuit analysis, network analysis (thevenin/kirchoff theory and applying those), learning practical design patterns and reducing new schematics to these patterns as much as possible.

And reading electronics magazines in free time. Gasping at schematics for hours . Nothing can replace that.

Harold, the theory of operation,and the choice of components, is often recorded in the design documentation and in the engineer's notebooks.

The part of that info that's needed to repair the design is then published in the service manual.

The other parts of the theory aren't public for many commercial designs.

Hi Harold,

A lot of it is whim. For simple circuits like this one there are many components which could be substituted for the ones chosen and we would get the same results. Sometimes it is what is at hand or perhaps the designer has had luck and experience with a component in previous builds. They call it the Art of Electronics and just as an artist can pick colors and brushes the electronics designer can choose components. As the function of the circuit becomes more critical and the desired output more precise the range of usable components will begin to narrow and the choices of design become more critical as well. As with all things in nature each choice has its good attributes and its side effects. If your acceptance of tolerances is relaxed you can build a circuit quite cheaply. As you push the stability and precision of what you are trying to do to smaller deviations the difficulty and the cost rise quickly.

You have not been able to find a simple tutorial as there may not be a simple answer. The best way to understand the voltage and current in a circuit is to build the circuit and take the measurements. If you can do the analysis and math to make the predictions ahead of time all the better as you will have the ideal theoretical to compare against the empirical. Then you can investigate and speculate on why they do not match.

There are a lot of people like me designing simple circuits who do not really know exactly what we are doing. That is alright and I am not ashamed of my relative design ignorance compared to many of the great engineers on this forum. I am a student and a learner. Most of my designs eventually work and do what I want them to do. Many times it is due to the help of the guys and gals on this forum who help and give advice without trying to judge or put me down.

Before I get done with a design it has usually been redesigned and it may have parts that do not greatly effect its operation. Some of these parts are there to protect other components or to slightly improve the stability of the circuit. If a large spike happens to occur a flyback diode is there to protect the semiconductor device but if you take the flyback diode out of the circuit it may still work just fine, at least for a while.

The question you seem to be asking can not be easily answered with a tutorial. If you pick a complicated circuit and ask why was this resistor value chosen the answer may depend on the earlier choice of other components which in turn were dependent of the choice of others.

Here is an example: I have two circuits where there is a battery and two resistors in series. In the first circuit I choose a 1K resistor for one of the two resistors. What must the second resistor measure to give me a voltage of 1/2 the supply at the junction of the two resistors. The answer is another 1 K resistor. Now suppose I choose a 10K resistor for the first resistor. Now the second resistor must be 10K to give me the same voltage at the connection between the two resistors. You can see that my second resistor always depends on the choice of the first resistor and in fact the choice of the first resistor is dependent on whether I have a need for a specific amount of current to flow in the circuit. It is a process and most of the times there are many ways to get to a desired result.

In some ways asking why a specific component is being used is like asking an artist why he chose a specific shade of green for a particular brush stroke.

If I still haven't gotten close to the answer you are looking for perhaps one of the engineers will drop a little wisdom on us.

John