Electronic Component Explanation

[DragnsBane]

I been looking around in a few text books and have not been able sort out some of the component explanations, so I have a few questions.

1. I know resistors resist the flow of electricity in accordance with their ohm rating. However are there other purposes for the resistor?

2. I have noticed on almost all the schematics I have looked at that the capacitors are always put on a ground wire. I know the capacitors are their to help with voltage spikes and smooth out the power surges. Are there other purposes for capacitors in the circuit besides this? And what are they?

3. On the transistors, such as the IRZ44, they basically act as a signal amplifier, right?

4. I also noticed on the IC's that the some of the outputs are are labeled RA1, RA2, RB3, etc. What do these mean?

I know alot of people might be happy with just a basic explanation to get them started. Who knows, someone who reads this might come up with a new type of controller that will be the hottest thing out.

later all,

[arvidb]

1) Resistors' only use is to act as resistors (i.e. limit the flow of electricity). The formula for how a resistor affects a circuit is called Ohm's law and is U=R*I. This means that the voltage over the resistor equals the current through it times its resistance, or equivalently that the current through it equals the voltage over it divided by its resistance.

2) Capacitors act as a short circuit for high frequency signals and as an open circuit (= high impedance = high "AC resistance") for low frequency signals. As you say, this can be used to short transients to ground, and huge capacitors are also used as a power reservoir in linear power supplies (essentially blocking the huge from-0 V-to-full-voltage transients of the rectified DC). These characteristics (blocking of LF and shorting of HF) can also be used together with resistors or inductors to form frequency filters, for example in audio the filters in speakers dividing the LF to the bass drivers, middle to the mid driver, and HF to the tweeter.

3) Are you asking about the transistors or the capacitors? Transistors act basically as a signal amplifier, yes. Capacitors can be added in series with the base to block low frequency signals or DC, or in other ways to block high frequency noise and stabilise the circuit.

4) You will have to look at the IC data sheet to find the meaning of the different pins of that specific IC.

Arvid

[Ferenczyg]

Originally Posted by DragnsBane 4. I also noticed on the IC's that the some of the outputs are are labeled RA1, RA2, RB3, etc. What do these mean? later all,

that is normal for microcontrollers, and is derived from the name of the ports. this way, ra1=port a pin1, rb2=port b pin 2 and so on. If you look a schematic with a pic microcontroller or atmel avr microcontroller that is the way to name the signal pins. other pins have specific names like osc for oscilator, or rst for reset, or int for interrupt.

/Fer

[DragnsBane]

thank you to you guys. i was reading up on some of the components and was having some confusion over the low and high frequqncy filter. the way it was explained in the text i was reading the resistors themselves were used as the filters now that i ubderstand a little better i should be able to move a little futher forward with what i'm working on. now to get up to speed on eagle.

later all....

[Mariss Freimanis]

DragnsBane,

You cover too many topics, each of which would take many books and years to cover.

Let's start with the first one.

In all of electronics there are only 3 types of components; resistors, capacitoirs and inductors. That's it. That is all there is.

These are called "passive" components. Everything else, transistors, diodes, etc, ICs, are called "active" components.

To design anything requires you to completely understand the passive ones first. Were you to take an electrical engineering major in school, this is where you would spend your first two years on. On passive components. They are that complex in their interaction with each other.

You would also learn, live and completely understand higher mathematics. You would start your freshman year, first quarter, with integral calculus. You would have math that would go on from there every single quarter you were in school until you graduated. Why? Because it is the only way to understand and describe the interactions between R, C and L, the passive components.

Semiconductor theory would show up about your junior year. You would by then be so steeped in math it would seem easy.

If you are not up to this, there are other ways. It can be self-studied. This stuff is not that hard to understand but you really have to undestand calculus if not love it to make a go at it. Without calculus or an innate understanding of what it is, you really can never make headway in electronics.

The rest of the stuff you asked about really won't make any sense until you deal with the above. This is not a subject you can "ask some questions to get started" and then go from there. It is a truly hard and difficult science.

I started with an ARRL (Ham Radio Handbook). The preface (all 100 pages) covered all of what I needed to start with. The rest of what I was missing encouraged me to go to school and get my degree.

Good luck.

Mariss

[HuFlungDung]

Ah, yes, oh for another life to take a different tac with

[unterhaus]

Originally Posted by DragnsBane I know alot of people might be happy with just a basic explanation to get them started. Who knows, someone who reads this might come up with a new type of controller that will be the hottest thing out. later all,

This line made my day. I have a Ph.D. in Mechanical Engineering. Since I specialized in control theory, and have messed around with electronics as a hobby, I have a really good knowlege of electronics. However, I would hate to compete with Mariss.

I think maybe Mariss overstated the case a little, but the amount of time to really become successful at designing circuits is equivalent to an undergraduate degree. After all, a lot of circuits are made up from circuits copied from app notes. However, if such a design doesn't work, you better have a solid understanding of the dynamics of the underlying circuit. And to design "the hottest thing out," an EE degree is probably the bare minimum requirement.

The controls world has pretty much switched over to digital. The analog/passive circuitry is much simpler, but the theory is no easier.

The ARRL handbook is a good start. Also very useful is Horowitz and Hill "The Art of Electronics"

[DragnsBane]

I jope no one takes this personally, but I think college is overrated. I spent five years as a machinist and found many problems with the designs of mechanical parts designed by mechanical engineers with many years of college experience. And know that I work as a union carpenter, I continue to find many problems with the designs of of buildings and the bridges I work on. I do believe if someone is willing to put in the time and do some reading than it is possible to design things without the need for a very expensive college degree.

later all...

[unterhaus]

I make mistakes every day. Anyone who claims not to have done so has probably left some big ones for someone else to clean up. But does finding a mistake in a drawing of a bridge mean you can design a bridge? There was a tragic accident at a hotel years ago where the designer of a foot bridge designed a detail that couldh't be built. The people who built it came up with their own modification and it collapsed. If the engineers had experience building things, they may not have made their mistake, and if the builders had respected the difficulty of engineering the bridge they might not have made their mistake. I know a lot of engineers are arrogant and look down on the trades, which is a horrible mistake. But any time I find myself looking at someone else's trade and saying "oh, that's easy," I know I'm kidding myself.

The way I learned electronics was to build things from other people's designs. The first circuits I built were for guitar effects by a guy named Craig Anderton, who I'm almost positive does not have a college degree. There are plenty of designs in the open source section of this web site. I suggest that you get comfortable building something like that and then trying to figure out how it works.

But I'll answer your first question. In the following, V = volts, I = current, C = capacitance, L = inductance. d_/dt is the time derivitive of _. For example dI/dt is the instantaneous change in current.

Passive components are fairly simple. The thing that makes it interesting is combining them. The rules for combining circuit elements are:
1. Things hooked up in parallel have the same voltage drop across them.
2. The sum of the currents into a point in a circuit equals the sum of the currents out.

Everything you need to know about a resistor can be encapsulated in V=I*R. Of course you can't exceed its power rating, the power dissipated in a resistor is P=I*I*R

The ideal model of a capacitor is I=C dV/dt. What this says, if there is no change in voltage, there is no current. The two most common uses of capacitors is current blocking (capacitor in series) and filtering (capacitor to ground). Capacitors have a voltage rating that can't be exceeded. Capacitors in combination with resistors are used in all sorts of interesting ways, as differentiators, integrators, and filters.

The ideal model of an inductor is V=L dI/dt. This says if there is no change in current, there is no voltage drop across the inductor. Conversly, an inductor resists big changes in current. Inductors have a current rating that cannot be exceeded.

At this point an engineer would generally drop the time domain (d_/dt) and go to Laplace transforms. I'll skip that for now.

All three of these devices can be used in combinations as voltage dividers. If you learn to spot voltage dividers in all their combinations, you have a step up on a lot of people.

[sbrpollock]

I am what the local trades refer to as "multicraft", meaning I am qualified as an electrician and as a millwright both and have the experience to back it up. ( I don't call it multicraft, I call it "Union Busting", But that's another issue )

I used to cuss engineers on a daily basis. I hated engineers.

I just recieved my first college degree in Electrical Engineering in the beginning of August.

In other words I had the experience first, then I went to college and got the degree.

I can tell you they are NOT THE SAME!

I don't think Mariss exaggerated much. I learned the theories that have been laid out here quite well.

I think though that the largest lesson I've learned earning this degree is just how LITTLE I really do know!

[ToyMaker]

I started playing with electronics (radio and tv repair) in the late '50s. Over the years I have had my fingers in (still have them all ) electronic, electric, electromechanical, pneumatic, hydraulic, and computer equipment and systems. Finally got my (computer science) degree in '94.
I am learning new things every day. And every day, like Patrick, learning how much I don't know.

robotic regards,

Tom
= = = = =
"What great fortune it is to have a friend who is like a brother and a brother who is like a friend."
- - Bob Sharton

[Mariss Freimanis]

Congratulations, Patrick! I think the best EEs are ones who started as techs. Mine is a prejudiced view because that is how I started.

Everyone makes mistakes. Yes, bridges and buildings collapse, space probes miss their marks and there are mechanical drawings that cannot be turned into metal. That is not the point. At worst it means the practioner does not have the snout to tail understanding of his proffession needed to go from concept to finished product. The "tail" is having hands-on practical experience how to execute that great idea after you have designed it. Former techs have an advantage here that green behind the ears, no previous experience, freshly-minted EE must eventually learn.

My post was about what knowledge is necessary to design. For that, think of electronics as an alien language where even the alphabet is foreign. Like any language, you can pick up a word or two, maybe even speak it enough to be understood. To be fluent though, you have to be able to speak like a native and write and read in it as well. You can be self-taught but the easiest way is to take a formal education. That insures you have all the tools needed for full proficiency in the shortest amount of time.

Mariss