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rstofer:

--- Quote from: lefty on January 26, 2020, 06:27:42 pm ---Right. I may be a bit premature since I just started tinkering around.

--- End quote ---

There are two different ways to play with electronics:  'Tinkering' and 'Designing' and, as you can imagine, designing is a lot more complex.  From a tinkering point of view, the Internet is full of projects that are fun to play with.  Designing from scratch takes a lot more knowledge of theory and, of course, math.

This forum is loaded with working EEs.  If you want to know something, this is the place to ask questions.  Somebody will know just about all there is to know about whatever it is you want to know.  The various forums on EEVblog are about as friendly as it gets.

Dave has some great videos, I especially like the Fundamentals Friday series.  When you get to op amps, watch Dave's videos including #600:

https://youtu.be/7FYHt5XviKc

Or the equally good videos from W2AEW including #75

https://youtu.be/K03Rom3Cs28

Now, maybe op amps aren't really of interest at the moment but a couple of concepts will be:  Ohm's Law and Kirchhoff's Laws.  Dave does a great job with Kirchhoff's Current Law in that op amp video.  It's absolutely magic the way the inverting input works.  And you will absolutely need Ohm's Law, Kirchhoff's Laws, Norton's Theorem and Thevenin's Theorem.  These are the fundamental tools of electronics.  Khan Academy Electrical Engineering curriculum can help.  As can all the other YouTube sites that deal with this stuff.

If you truly understand those 4 items, you will be far ahead of the average tinkerer.  Just understanding the negative feedback in video 600 moves you a long way down the road.  Op amps are magic!


lefty:
Thanks for the encouragement. I've taken some online ed for electronics over the past couple weeks and have been watching a boatload of videos on youtube. so I'm still learning the basics and am truly a beginner. We'll see where it takes me. I might be a little too old for a new hobby/interest. I've been using everycircuit.com a bit, which I'm sure all here are aware of. I find it helpful as a lot of the early education is pure math. It's helpful to see how the math actually works in real life.

rstofer:
I have never stumbled across EveryCircuit.com - interesting!

Most of us use LTspice for simulation.  TINA is another choice but not as common.  There are a lot of LTspice tutorials and there is a group over on Groups.Yahoo.com and there are a couple of fellows that are REALLY knowledgeable.  Which means, they are a week ahead of the rest of us.  Seriously, one of the moderators has direct access to the author.  It's free, BTW.

Circuit animation has its proponents and, unless it gets annoying, I kind of like it too.

Side comment:  Electronics is applied mathematics.  The nice thing is that much of what hobbyists want to do can be done without a whole lot of math.  A little algebra goes a long way!

One thing to remember:  Simulation is an hallucination of how a circuit might operate if the world was perfect.  And it isn't.  In general, simulations don't account for parasitics, they certainly don't account for what a breadboard does to performance and they rarely account for tolerances.  Simulation lives in a perfect world and we don't.  Don't be surprised when there are differences when you get to measuring things.

The real trick is to account for the differences.  What kinds of things in the physical world are causing the deviation from the simulation?

But it's all good!  There is a bit of education in everything!  It's even worth simulating the early DC Circuits where there are multiple power sources and several resistors.  Just to see if the simulation agrees with the math.

When I was stumbling through college back in the early '70s, I would have loved to have the tools we have today.  Then the emphasis could shift from trying to solve the stuff with a slide rule to actually understanding the material.


lefty:
I appreciate that. The simulation is definitely helpful. I'm really stubborn when it comes to learning. I'm not satisfied with knowing how, I have to know why. The why isn't always available at the very beginning of learning something. I know it probably slows down my progress a lot of times when learning new stuff. I have a breadboard, some various components and such, odds and ends I picked up online in a kit.  But it's helpful to see it in some sort of action before I start a fire at my desk. I'm working on a power supply right now. Trying to figure out if I'm going to build one or buy one. I have several power supplies in my computer graveyard I've collected over the years. I figured I'd check out the equipment forum and then decide.

I downloaded LTSpice and will take a look at that as well. Thanks for the tip.

rstofer:

--- Quote from: lefty on January 27, 2020, 11:32:51 am ---I appreciate that. The simulation is definitely helpful. I'm really stubborn when it comes to learning. I'm not satisfied with knowing how, I have to know why. The why isn't always available at the very beginning of learning something.

--- End quote ---
Sometimes the 'why' isn't taught because it is assumed that the learner doesn't have the math skills to deal with calculus up to the level of differential equations.  We just toss out the current in a capacitor is C*dv/dt and there is no particular emphasis on dv/dt. From the equation, the current can get very high when dt (the time interval) gets very short - down in the ns region.  The thing is, there is parasitic series inductance that limits the current and there is series resistance as well.  The current can't get anywhere near that high.

On this topic, the LC Oscillator in EveryCircuit shows how the circuit oscillates but is totally unrealistic in the real world.  There is series resistance, intended or not, that dissipates energy and ultimately collapses the amplitude.  But the simulation doesn't show that!  It could be added, of course, and then you wind up with the more familiar form of Damped Harmonic Motion.  Again, the simulation isn't anywhere near reality.  It's just a thing with me...


--- Quote ---
 I know it probably slows down my progress a lot of times when learning new stuff. I have a breadboard, some various components and such, odds and ends I picked up online in a kit.  But it's helpful to see it in some sort of action before I start a fire at my desk. I'm working on a power supply right now. Trying to figure out if I'm going to build one or buy one. I have several power supplies in my computer graveyard I've collected over the years. I figured I'd check out the equipment forum and then decide.


--- End quote ---

I bought a Rigol DP832 a couple of years ago and it's a great supply - but it's pricey.  For decades I got along with batteries and wall warts plus the occasional fixed output supply - usually 5V.  PC supplies aren't highly regarded but if you plan to use one, at least fuse the outputs:

https://www.sparkfun.com/products/12867

There are MANY PS projects around here.  A few of them actually work properly but most have problems getting down to 0V and the current limit doesn't seem to be 100% successful.  You can build up fixed voltage supplies using something as simple as an LM7805 but why bother?  You can buy a 5V wall wart easier.  Everybody tries to make a DP832 in terms of functionality without really understanding how it works.  There's a reason they are expensive and it starts with that custom toroidal transformer with multiple secondary taps.

Another big difference between low end and high end power supplies is the way in which the current limit is set.  On the DP832, I just dial in a number.  On a low end PS, you short the output and set the maximum current.  For some reason, I don't like the idea of shorting a 12V 3A supply.  Maybe it's just me.

ETA:  Try to avoid switching style wall warts.  That is not always possible at higher currents but linear supplies will have less noise.

Here's a nice supply for breadboards:
https://www.seeedstudio.com/5V-3-3V-Breadboard-Power-Supply-p-566.html

DigiKey has the same kind of thing but I'm having a problem with their site right now.

Another approach:
https://www.sparkfun.com/products/114

I have some of these:
https://www.mouser.com/ProductDetail/Bud-Industries/BBP-32701?qs=sGAEpiMZZMve4%2FbfQkoj%252BN1%252BOwm3e8RAmsQ2NWu9W78%3D

Yet another approach:
https://store.digilentinc.com/powerbricks-breadboardable-dual-output-usb-power-supplies/

There a lot of ways to get power to your project without spending a lot of money on a power supply.

OTOH, the current limit and current trip feature of a modern supply (like the DP832) will save you a lot of escaping smoke problems.  Of course I recommend a decent lab supply but they are too pricey and maybe they can be deferred for awhile.


--- Quote ---I downloaded LTSpice and will take a look at that as well. Thanks for the tip.

--- End quote ---
There are books about LTspice -- I haven't read any of them.

Another idea:  Instead of spending a lot of money on a lab power supply, why not spend it on a good oscilloscope?  You will need that a lot more than you need the features of a lab PS.  The Rigol DS1054Z is on my bench (as is a Tektronix 485) and it's a GREAT tool but it's getting old.  Search Test Equipment for riglol (spelling IS correct) and follow along to get the 100 MHz feature unlocked.

The new Siglent SDS1104X-E is newer and apparently a lot easier to use.  I think there is a thread over in Test Equipment on how to unlock the 200 MHz feature in a 100 MHz scope.  Saves about $300...  The Rigol was available when I went shopping.  Today I would probably buy the SDS1104X-E or spend the money for the SDS1204X-E

I would highly recommend 4 channels.  That is the specific reason I bought the Rigol - two channels won't display all the signals of an SPI serial transaction.  That the scope also decodes the data is a plus.

https://siglentna.com/digital-oscilloscopes/sds1000x-e-series-super-phosphor-oscilloscopes/

https://www.amazon.com/Rigol-DS1054Z-Digital-Oscilloscopes-Bandwidth/dp/B012938E76  Easily unlock for 100 MHz!

It's easy for me to spend other people's money!

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