AVR-Chat

Hi David, I was an electronic teacher in the past, with many students and
their problems to understand what seems to be a monster, and it is only a
bunch of different information and concepts.

Let me try to help you in this your new endevour.

If you want to get the basics of electronic (what I would recommend), you
should forget a little bit about microcontrollers, processors, memories,
etc.  The similarity is if you want to understand how to build a car from
scratch, first you need to understand how to cast iron, vulcanize rubber and
mold plastic, each different temperatures for each material, problems and
solutions for each one.  To purchase parts from the store and put the car
together is easy, anyone with a minimum mechanic skill can do it, mostly
because you can buy a working engine, attach to a working transmission and
connect cables and hoses, you can have a complete car working in few days,
but the question is;  What did you really learn? just put a car together,
nothing else, you didn't learn how "to build" a car at all.

Of course that you don't learn how to build a microchip, but you need to
understand how to build a 1/1000000 part of it with few transistors, leds,
capacitors, regulators, understand power supply, power control, how to
calculate transistor polarization, current, amplification, invertion, etc.

In a easy way, and "easy" is never the same for "simple" (they never walk
together), I would ALWAYS start to teach about a simple POWER SUPPLY, using
a power cord, switch, fuse, power transformer, rectifiers, capacitors,
voltage regulator and output posts.  That is the most simply electronic
buildup you can do, most students create a solid desire to keep going when
their FIRST power supply works nicely.  They feel confidence and understand
the first concepts of electricity and electronic, alternate current, direct
current, voltage conversion, interruption, safety, conversion from AC to DC,
filtering and regulation.  Everything in only 7 different electro/electronic
parts.  All those 7 (8) parts can be purchased at any Radio Shack and would
cost  no more than $15.

I would take a whole day or two to understand exactly, in details, with
fully understand, about how each one of those 7 parts work and what happens
if they are assembled wrong, or reversed.  By this way, the most basic
principle of any electronic project will be solid in your mind, not only how
it works, how it should be built, but further, what happens if something was
built wrong, or if something fails or short circuits in that power supply.

After that I would recommend start playing with resistors, leds, calculating
resistor values as current limitters based on the Ohms law, led
specification, etc.  At this point you understand the second most important
part of the electronics, how to avoid a disaster and how to control current
and generate voltage drop.

Once you have the above solid and very understandable (if you cheat, will be
cheatting to your future), then you may try to understand how to polarize a
transistor, few resistors, perhaps a solar sensor or a LDR to make a LED
lite when  it gets dark.   When you dominate this easy task, would be
feeling very satisfied to do something that less than 1 in 1000 people in
the planet can do.

Then you will learn that the LED can be replaced by a relay and you for sure
will be able to automatically turns on a 100 Watts lamp at your backyard
just because it is after 8pm.  I guess just 1 in 5000 people can do that
without copying a circuit from somewhere else.

At this point you can turn to digital electronics, forget about power
supply, transistor, LDR, etc, and buy a dozen different microchips from the
74HCXX series, you can invest $30 there and have a box full of surprises and
adventures.  At this point the previous knowledge from LEDS, resistors, etc,
will help you to build the visual output of your digital crazyness.  Few
switches and buttons will create the evil control of the beast.

Understanding the basic concepts of logic gates will give you a nice
opportunity to open a door visited only 1 in 10,000 people.  At this point
you will be able to play with latches, counters, then you will desperat
after some 7 segments displays and some decoder bcd-7seg to show numericaly
your brain teaser designs.

Then, only then, you will think that the switches and buttons could be
replaced by your microcontroller port output and input pins, so your
electronic digital design now is controlled and possibly read by the
microcontroller, and the transistor and relay now will switch on the 100W at
the backyard not only because it went dark, but also, because it is exactly
10:25pm, time to get the dog out, and the light will be off at 10:40, after
you came back, not only that, at 10:42 the backyard alarm will be activated
and so on.

What I mean is that a good Formula 1 driver absolutely needs to know what
happens at the engine when he presses the gas pedal, not only that some
cable is pulled and fuel injection happens and the hell is unleashed inside
the pistons, he needs to know why and how it happens and recognize when it
is ok or something is not good.  He needs to count with his knowledge, more
the better, to win a race.  Nobody wins a race just because he was there, he
did it because in some way he was prepared to do it.

My first anything electronic, a power supply, in 1969 started with a flat
aluminum plate 4mm tick.  Saw, hammer and drill.  I had no idea what would
happens after that. It just changed my life.

Cheers and welcome.

Wagner Lipnharski - email:  wagner@ustr.net
UST Research Inc. - Development Director
http://www.ustr.net - Orlando Florida 32837
Licensed Consultant Atmel AVR _/_/_/_/_/_/
July 2, 2004 2:54 pm






David Brännvall wrote:
> Hi, I have been into programming for several years, but now I want to
> start with hardware. My first project will basically be a little
> general purpose box with lots of buttons and leds and a display, and
> a comport.
>
> I have bought the stk500, and I have no problem with the assembly
> programming, and I manage to connect a few leds 74XXX ic's etc to the
> stk500, and get some comport communications with my pc etc.
>
> But I feel my electronics skills are way to low, I need to learn
> things like:
> * More basic understanding about the electronics.
> * How to control things that require more current then the stk can
> provide.
> * How to build things without using the stk500.
> * Howto read datasheets.
> * Howto find errors in my hardware designs.
> * Etc
>
> Ie The programming isn't any problem, but I don't know enough to
> design my own hardware around the AVR.
>
> I just need to get some basic knowledge, so I can experiment. Right
> now I get stuck all the time, and I don't know what to do, or where
> to look for the solution.
>
> The avrfreaks website is great, but most of the information is about
> programming or the electonics is to advanced for me.
>
> It can't be impossible for a newbee like me to design the "simple"
> box I mentioned.
>
> It should be just some shiftregisters to set the leds, some
> shiftregisters to read the buttonstates, some io to the display and
> the comport.
>
> But I don't know where to put the resistors, how to get enough current
> to drive the led backlight and stuff like that.
>
> Any ideas where I can find info to learn more about electronics, ie
> webpages, books, tutorials, newsgroups, irc, anything that might help
> me.
>
> Regards,
> David
>
>
>
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