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Topic: Changing power source (Read 1 time) previous topic - next topic

retrolefty

#15
Jul 19, 2011, 12:51 am Last Edit: Jul 19, 2011, 12:52 am by retrolefty Reason: 1
Quote
That might smoke some external components, but I can't see how that would fry the Arduino/Atmel chip itself.


Well AVR I/O pins do have a maximum safe current limit where if exceeded, real damage can happen. Just for a academic example wire two I/O pins together, set them both to output mode, set one high and one low and then touch the chip. If I tell the compiler to do that it will, so the compiler in my hands can damage stuff if I have a brain fart, and that's been known to happen from time to time.  ;)

Lefty


smeezekitty


Indeed, some people (who are too clever for their own good, IMHO) use multiple I/O pins tied together to increase the current capacity. Of course, that requires that you can switch them all REALLY simultaneously.

Clever? Hardly. I don't think it is a good idea. BTW You could use e.g. PORTB |= and PORTB &= to toggle multiple pins within a us.
Avoid throwing electronics out as you or someone else might need them for parts or use.
Solid state rectifiers are the only REAL rectifiers.
Resistors for LEDS!

retrolefty


Indeed, some people (who are too clever for their own good, IMHO) use multiple I/O pins tied together to increase the current capacity. Of course, that requires that you can switch them all REALLY simultaneously.


Well my point was that even simple human error in specifying pin numbers or pin mode to something wired to real world external components or modules can cause damage to either the AVR or the external circuit or both. A compiler is a powerful tool, but with that power comes risks, especially to some of the target arduino market, people new to programming and electronics. Directly controlling external transistors in a H-mode configuration can be destroyed with errors in programming logic that the compiler will happily compile error free.

Lefty

justjed


Quote
Also, on the topic of "free", there's a distinction, poorly conveyed by the English language. There's "free, as in freedom", and "free as in beer".


IMHO, that is an debatable distinction.  Most things we consider or call "free" were paid for by somebody back along the line somewhere (including freedom itself).


Well, we're off into some perhaps debatable semantic distinctions, but nonetheless, that distinction is a canon in the Free Software community. (And, there's the endless debate about "Free", vs. "Open", about which you can read more, if you like, by starting with luminaries such as Richard M. Stallman (Yes, "RMS") and Eric S. Raymond (often referred to simply as "ESR"). In terms of "paid for", well, yes, in fact, sometimes there is pay involved. Many contributors to the Linux kernel, for example, do so while on the payrolls of well known companies, like IBM (Ted T'so). However, "pay" in the context of Free Software, is really a non-monetary thing. Probably, ESR explained it better than anyone else I've encountered, in his book The Cathedral and the Bazaar. Here's a blog post touching on the gift economy aspect. Nearly the entire book is available free online. (And I highly recommend it)

"Free as in beer", meaning "at no charge" obviously is a time-bound thing. And if someone gives me a gift, well clearly there was a cost there at some point. But in the moment of the gift, it is free.

But with Free Software, part of what happens in the gift economy is that somebody will see a need (even if it's just a singular, personal need) for some piece of software, and just write it because he (or she) needs something that does that. But then, in acknowledgement of having the use of lots of Free Software (e.g. Linux and the GNU toolchain), that person decides to give back to the community, and releases the code under an open license. This winds up being both a pay-it-back and a pay-it-forward. And the cycle continues. Does that make it "paid for"? In a sense I suppose, except that I think most of the developers think of it more along the lines of "share and share alike".

And, particularly within the Arduino community, I think we can appreciate the distinction, since we're working on an open hardware platform. In fact, this forum is a little self-contained gift economy as well. Is the advice given by folks such as Crossroads and GrumpyMike "free"? I would say it is.


So while you may give me a free beer, I may not be able to freely drink it for other reasons? Say I'm the car pool driver, etc.  ;)


With great freedom [or beer], comes great responsibility.  8)
... it is poor civic hygiene to install technologies that could someday
facilitate a police state. -- Bruce Schneier

smeezekitty


And time is, arguably, the most precious commodity of all.

Agreed.
Avoid throwing electronics out as you or someone else might need them for parts or use.
Solid state rectifiers are the only REAL rectifiers.
Resistors for LEDS!

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