Education/Development/Project/Prototyping system?

[PlaneCrazy]

I'm new here, and I'm also from a mechanical background. If I had more time I'd have invested in a proper electronics course/diploma/degree, but alas.

Can anyone here recommend a project or development system I can use to learn (step by step) and experiment on everything from cells and resistors, capacitors, inductors and diodes, right through to IC, micrcontrollers and microprocessors? It will serve me personally, as well as professionally.

Thank you in advance

 

[KeepItSimpleStupid]

There are some say 50 in 1 or 200 in 1 kits that I used as a kid. It's kits to build, but not necessarily understand.

there are some military electronics courses online that are decent.

www.microchip.com offers a vast amount of information on their website.

Publications such as Elecktor, Circuit Cellar (advanced), Nut's and Volts, Silicon Chip are also helpful.

 

[PlaneCrazy]

I have access to Elektor, but I don't understand half of it - their explanation is either too high level, or too black box. I have several text books on the subject, but need some practical tools. For instance, what transistor/op-amp/diode/IC/resistor etc. do I use? What's the wetting current/driving current/minimum current, and why? How do I choose? How do I know beforehand that I will/won't/might fry my circuit, or watch in awe as nothing happens?

The alternative is to annoy everyone at this site with stupid questions like "I want to do this and that, my power source is sis and so, my signal is bla bla, you fill in the rest and give it to me..." hundreds of times over, or until I'm banned. And I may have to buy small bits of component sets and mess around to see what makes the smoke come out until I figure out how to keep the smoke inside.

Thanks anyway. If I knew more about my problem, I'd be better able to explain it - or not need to in the first place...

 

[SABorn]

I think most of us here have let the smoke out of more than we would like to admit to and we still do.

The only dumb question is the one you dont ask.

We all start somewhere, and i see no problem with plagueing the forum with basic questions, there is always someone who can answer them, and at times it allows lesser skilled members to help someone with information that they have just learnt themselves.

I would say start with a few leds and resistors plus a battery, a bread board which is a solderless circuit board would be a good item to get, as you can then plug components in and link them together with short wires to construct a circuit.

Pete.

 

[PlaneCrazy]

Again, how do I know what LEDs, resistors, transistors etc. to buy? In my mind, P(thermal) = I^2.R = smoke comes out, so I would by default purchase the biggest resistors I can find, say 1M. But how do I know that this won't allow too little current for the rest of the circuit to work?

I'm soon going to post my first official project, that is job-related and not interest-related. I have lurked and searched this forum, but it would seem that the lm3914 is and always will be a *******...

 

[SABorn]

Resistors you need to get a range of various values from say 10 ohms up to 1 meg ohms, 1/4 watt resistors are about standard, if you look on ebay and other places you will find resistors in packs of mixed values.

Well it wont matter much what leds you get, just go the cheapest and it wont matter if you do kill a few...red and green are about the simplest.

As for using leds and resistors.........look up Ohms Law, print it out and keep it handy, learn it as that is what we all use to determine what resistor to use with a led.

For example we have a red led rated to 2.2 volts at 20mA and we have a 6 volt battery power supply and we need to work out what resistor to use.......ohms law!!!

6 - 2.2 = 3.8
3.4 / 0.020 = 190

So we need a resistor 190 ohms, but we would find it hard to find a 190R resistor, so we use a 200R or 220R resistor.

Simple Ha??

Pete.

 

[KeepItSimpleStupid]

Wetting current wasn't covered in school, so what is it?

It will show up when looking at the specs of mechanical switches and relays. It's a minimum switching current that you need to design for. Why? Oxide builds on the contacts and exceeding the wetting current reliably renews the contact surface. 10 mA is a good number in the absence of data.

Minimum and driving current needs to be seen in context.

 

[crutschow]

First you need a good working knowledge of the basics such as Ohm's law, series and parallel circuits, Kirchhoff's circuit laws, basic inductor and capacitor equations, etc. If you don't have that, then that's where you need to start, before you try to experiment much with circuits. Otherwise you are just flying blind. Wikipedia is a good place to start.

A simple way to experiment with circuits it to use a circuit simulator (LTspice is free and works well). That way the smoke is all virtual. You can start with simple circuits and probe the currents and voltages to see how they work. You can continue on into using transistors, op amps, and more complex circuits as you progress. If you get the circuit to work properly in the simulation, then there's a very good chance that is will also work when you build it.

 

[KeepItSimpleStupid]

OP amps

One thing that's basic is called the gain-bandwidth product. and the notion of bandwidth. The -3db frequency or when then gail is 0.707 of an amplifier's nominal gain. It's the basic characteristion of a simple RC filter where 1/2(PI)fC is the -3 db frequency.
bandwidth is usually defined for A=1. and bandwidth * Gain = some constant.

Op amps come optimized for various parameters and some examples are:
1. input bias current
2. Bandwidth
3. Single supply
4. Dual supply (watch valid swings)
5. Rail to Rail
6. Low power
7. Low offset V
8. High current
9. High voltage
10. A current mode (Norton OP amp)

The type of input FET or BiFET and the type of output (bipolar transistor, FET). FETs for an input stage give rise to a low input bias current but with a strong temperature dependence. FETS on the output give rise to rail to rail op amps. Open Collector and Open drain outputs may be common with comparitor circuits.

The OP amp circuits (such as a summer) won't work properly unless driven by a low impeadence source.

Bypass caps, small capacitors located near the power pins of an IC are an essential part of a design. For now, use the manufacturer's suggestions and they MUST be located CLOSE to the IC. The closer the better.

Is that any help?

 

[Gary B]

A couple of really basic ideas that will get you going:
Ohm’s law: the voltage (E) across a resister, or across any DC circuit, is equal to the current (I) in amps times the resistance (R) in ohms. Everything else is just algebraic manipulation (I=E/R, R=E/I and the original E= IR).

Kirchhoff’s law: What goes in must come out and what goes up must come down. That is my paraphrasing. The first refers to current going through a point or junction. The second refers to voltages around a closed circuit.

 

[JimB]

Kirchhoff’s law: What goes in must come out and what goes up must come down.

Yes, that sounds like a good summary!

JimB

 

[PlaneCrazy]

First you need a good working knowledge of the basics such as Ohm's law, series and parallel circuits, Kirchhoff's circuit laws, basic inductor and capacitor equations, etc. If you don't have that, then that's where you need to start, before you try to experiment much with circuits. Otherwise you are just flying blind. Wikipedia is a good place to start.

A simple way to experiment with circuits it to use a circuit simulator (LTspice is free and works well). That way the smoke is all virtual. You can start with simple circuits and probe the currents and voltages to see how they work. You can continue on into using transistors, op amps, and more complex circuits as you progress. If you get the circuit to work properly in the simulation, then there's a very good chance that is will also work when you build it.

OP amps

One thing that's basic is called the gain-bandwidth product. and the notion of bandwidth. The -3db frequency or when then gail is 0.707 of an amplifier's nominal gain. It's the basic characteristion of a simple RC filter where 1/2(PI)fC is the -3 db frequency.
bandwidth is usually defined for A=1. and bandwidth * Gain = some constant.

Op amps come optimized for various parameters and some examples are:
1. input bias current
2. Bandwidth
3. Single supply
4. Dual supply (watch valid swings)
5. Rail to Rail
6. Low power
7. Low offset V
8. High current
9. High voltage
10. A current mode (Norton OP amp)

The type of input FET or BiFET and the type of output (bipolar transistor, FET). FETs for an input stage give rise to a low input bias current but with a strong temperature dependence. FETS on the output give rise to rail to rail op amps. Open Collector and Open drain outputs may be common with comparitor circuits.

The OP amp circuits (such as a summer) won't work properly unless driven by a low impeadence source.

Bypass caps, small capacitors located near the power pins of an IC are an essential part of a design. For now, use the manufacturer's suggestions and they MUST be located CLOSE to the IC. The closer the better.

Is that any help?

A couple of really basic ideas that will get you going:
Ohm’s law: the voltage (E) across a resister, or across any DC circuit, is equal to the current (I) in amps times the resistance (R) in ohms. Everything else is just algebraic manipulation (I=E/R, R=E/I and the original E= IR).

Kirchhoff’s law: What goes in must come out and what goes up must come down. That is my paraphrasing. The first refers to current going through a point or junction. The second refers to voltages around a closed circuit.

I know this, I know this too, and I know that as well. What I'm looking for is a practical approach. For instance, what do I use to apply Kirchoff's current law and/or voltage law over/around, say, a LM3914, or (later on) a microprocessor? In other words, I have a fundamental, theoretical understanding which helps me squat-all to actually assemble a circuit which may help me accomplish what I want to accomplish. How do I know that the pots and/or resistors aren't too big or too small? How do I know there's not too little current or too much current running through my system before I switch it on and watch either smoke coming out or nothing happening? How do I select components based on a conceptual circuit design? Obviously I cannot use the same components to build a three-phase induction machine variable drive as I would to build a guitar overdrive? Say I purchase the largest resistors. Will it not prevent too little current from lighting up LED? If I purchase the smallest resistors, won't I melt the breadboard or whatever else breaks down first?

I'm sure that there are others just like me who can't afford the help of specialists, or who don't want to divulge the secrets to a great idea to someone in a position to capitalise on it without any credit to the conceptual designer. Not that I'm implying anything...

I used to have this BlocTronics-kit which I could assemble any of the circuits there, but that wasn't useful for prototyping something. I could buy a breadboard or two, and have easy access to copper wire. But components are expensive here in SA, so I don't want to end up buying a whole lot of useless components (for my purposes).

I think I'll take a different approach: If I propose a circuit that does something, and use that to expand on the types of components, will you guys help me and answer my questions in a non-"black box" way to do the required calculations, so that I can learn how to select my components in this way?

 

[jerryd]

PlaneCrazy,

I'll take a different approach to your question because
you sound like the kind of person who, if you knew the very
basics, could figure out the rest.

There is a book called "Getting Started in Electronics" originally
written by Forest Mims in 1983. It's on Amazon or for sale at
some Radio Shack stores. It's almost as relavent today as it
was nearly 30 years ago.

There are some great reviews about this book on the internet.
Try this one:
https://www.robotshop.com/gorobotics/articles/reviews/a-review-of-getting-started-in-electronics

I was a mechanical engineer and got into electronics with this book.

Good reading,

jerryd

 

[PlaneCrazy]

Thanks, jerryd, I'll certainly take a gander.

I am good at figuring stuff out, but as far as electronics go, "figuring stuff out" usually translates to "destroying them until I give up, run out of components, or die trying". My budget and time doesn't allow this. The big thing with electronics is that I cannot prototype, I cannot rely on any simulations because they make as little sense to me as the magical components themselves. I cannot trace trajectories, use kinematics to determine the motions and then invoke kinetics to calculate the forces because nothing happens! I need to be able to use the theory I know and apply it practically, I need to know that something will work in practice before starting to build it. I need to know... if I knew what I needed to know I wouldn't have asked.

Anyway, some of the books we used during our undergraduate studies were by Nilsson and Riedel (Electric Circuits), and Roadstrum and Wolaver Electrical engineering for All Engineers. Good books, but insufficient. There was a third, but I can't remember the authors and I'm not going to look now. Even so, I know that there is a thing called a FET, e.g. JFET, MOSFET etc., but we only did some calculations with BJTs, and then only the T-model and the hybrid-pi model - I still don't know the difference between the two, how to choose between the two, or what power they can control vs. power they consume, what will destroy them and what will prevent them from working. I don't know where to apply power calculations to most electrical components, except electric machines, electromagnets and resistors (yes, I know P=EI=IR^2=V^2/R, but which does what where?). And then I still don't know how to calculate which wire to use to wire an electromagnet for use in an electric machine, or a field effect guitar pickup... When is a transistor a switch and when is it an amp? How much power during each mode of operation? And, get this: apparently an op-amp can be considered to be two transistors, while a transistor can be thought of as two op-amps! How do I use the information in the data sheet of some component to decide whether it will do what I ask it to do without getting fried, or being underpowered?

I'll say this again: electronic components do not cost fractional amounts in SA, the cheapest stuff go for several rand. I do not have money to waste on incorrect components. And simply copying other people's designs is not learning, it's copying. And the same goes for text books, which cost anywhere from R500 to R1000, even if it costs only a few US$ or GB£ in their local markets.

OK, I'll stop ranting, since I'm the only one apparently not making sense to anyone.

 

[PlaneCrazy]

Wetting current wasn't covered in school, so what is it?

It will show up when looking at the specs of mechanical switches and relays. It's a minimum switching current that you need to design for. Why? Oxide builds on the contacts and exceeding the wetting current reliably renews the contact surface. 10 mA is a good number in the absence of data.

Minimum and driving current needs to be seen in context.

Apparently the wetting current is also essential to reduce noise in audio equipment. How would I know to design for this?

 

[jerryd]

PlaneCrazy,
After reading your rant I am convinced "Getting Started in Electronics"
is the book for you. You can read and understand most of this book
in a week.

BJTs, Fets, JFets, MosFets, are all explained in less than overwhelming
language. As are capacitors, resistors, inductors, transformers,
transistors, diodes, Leds, digital and linear integrated circuits,
op-amps, etc.

Included are many simple circuits that you COULD prototype without fear
of blowing everything up.

All I've ever bought is a prototyping board, wire and some components
from Radio Shack and Mouser Electronics. I've attached a photo of my
microcontroller digital clock and propellor clock. Six months ago
I didn't know what a microcontroller was.

"Justin" on the prop clock is my 11 year old grandson who's learning
out of this book and can build most of this stuff himself.

jerryd

 

[PlaneCrazy]

That's great! Being upstaged by an 11 year old...

No, seriously, I'll have to get that book, thanks for recommending.

 

[fouadalnoor]

Hey I am pretty much a noob at all the electronic stuff myself (even though I just finished my 1st year electronics course...)

Anywho, the way I would start to learn all this stuff is just chose a simple project that you want to make. Something that is interesting, but not too advanced and does not need that many components (the one I chose is a simple gas alarm/flame detector).

In my circuit I have to use an OP-AMP, a PIC, an FET, a thermistor and a few resistors. Now the reason I know I have to use an OP-AMP is because I read about how they can compare different voltages which is good for my project as I want to compare whether there is a flame or no flame (just gas).

Now again, how would I relate voltages to whether there is a flame or not? well the thermistor comes in. It's resistance goes down when there is heat (i.e. flame). Now again, I can use my theory of OP-AMPS and resistors to do what I want.

I decide that IF there is a flame then I want the output of OP-AMP to have some voltage across it (i.e. the + terminal is larger than the - terminal) and if there is NO flame I want it to have no voltage on the output (i.e. my - terminal is larger than my + terminal).

The way it works now is that I keep the negative terminal constant (with two resistors making a potential divider) and the positive terminal changes again with a potential divider, although this time one of the resistors is the thermistor.

The values of these resistors is calculated by thinking about what voltages I want across the terminals and then using the potential divider formula.

What I just said may be a little confusing, but to sum it up...

1. Find out exactly what you want (in general not in detail, i.e. to detect a flame, turn on a motor after a certain time etc).
2. Think about what variables you have and what you want to detect/see/do (what do you want the Microcontroller's output to be after it's input is high or low?)
3. What components can you use and what are their properties?
4. How can you use each property of each component (i.e how can I use the Op-AMP's property as a comparator? what resistor values do I want in order to get the desired voltage across the terminals?)

I hope this helps!

 

[PlaneCrazy]

That's exactly what I was thinking to do in anyway. I'm not too keen on sharing secrets, but the stuff I had in mind will be harmless enough to share with the world. My first idea is one that relates to one of my favourite hobbies, remote-controlled aircraft. But the second, which relates to music, is the one I'm hoping to use to learn most of everything I may ever need to learn about the stuff.

Should I start a new thread, or continue using this one, though?

 

[KeepItSimpleStupid]

Start a new thread which basically states your a cluless noob and need lots of help. First: define the problem: Block diagram, what you know, what you don't. You can use "select audio source". Later, it might be use an analog switch to select the audio source. etc. Use what's called pseudocode: amplify signal x10, Z in 10K, Max output 1 V RMS.

You could start out as Build an equilization circuit for phono records. Support RIAA and eq curves for 78 RPM records and WAX recordings.
I want to support both MM and MC cartridges. etc.

In other words, submit a set of specifications to a "design engineer"

Designing is somewhat haphazzzard in the beginning. Look at this thread: https://www.electro-tech-online.com/threads/reversing-polarity-for-electrolysis-project.119652/

The above one is really based on a total newbie trying to design and simulate something until he get "stuck". Two designs come out in the wash. Research, Specs, test portions of the design physically, simulate, build a Bill of materials etc. It's all part of the process.

More simplification is possible.

You can get an idea of the process.

This one is even more conceptual: https://www.electro-tech-online.com...-output-and-0-1-microamps-100nanoamps.118755/

which is very conceptual at this point.

An article I read recently (two part) had to do with building an inertial guidance system for an RC plane. It was quite involved an fascinating.