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

Big Question here:

Where can I find how everything on this circuit works?

Whats the role of each component? Why do I even need a particular component? What happens to the current when it passes a component?

Please don't send me to a "how components works"  video that's not the question.

Hi Harold,

To determine the role of each component you will need to understand how each component works. There are lots of books that might help explain if you aren't interested in videos. I think the basis of your question though is how does electricity work. Voltage is a difference in energy levels and current is the flow of electrons that move to balance the difference. In the process energy from the moving electrons can change to other forms of energy like heat, magnetism, sound, light, kinetic energy, and potential energy. When current passes through a component this change occurs and when the current has passed through it either goes through the next component or it returns to the energy source that is producing the Voltage difference. If you get the hang of how electricity works and the laws that it follows you will be able to understand what is happening with each component.

John

Thanks, but in reality that's not how it works.

Let me explain myself.

One thing is theory.

Another thing is looking at the component on a simple circuit.

But the one thing I cant never find, is a single tutorial or lesson on the component role on a complex circuit board, and answer questions like: Why that specific component? why if I remove a component the results remain the same? why two transistors when only one can the the job? what components are there only for safety rather than another particular function?

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.

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

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.

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.

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.

Agree with all that!

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

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.

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.