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31  Using Arduino / Project Guidance / Re: Making more arduino projects without buying new arduino boards? on: April 16, 2013, 01:34:24 pm
Does anyone think they could duplicate this board for less costs?

While the price on those is truly awesome, they may not fit everyone's needs the way they sit.  There is a lot to be said for the custom approach for meeting a person's needs and it may be worth a penny or two.

This board below uses a shield PCB as the main PCB, it works well either way.  This one is going to be a custom board and there are additional parts to add.  But as you see it there, my cost is less than $9.00.  These are the main parts from my favorite store:

I've also built up a few of these with female headers for friends getting into Ardunio (actually, I got them to build them.  All part of the fun).  With a regulator and female headers they work out to about $12.00 and are basically a full featured Arduino that can accept shields and all.
32  Using Arduino / General Electronics / Re: Proposal: Newbie Guide for Electronics on: April 14, 2013, 09:25:09 pm have not right to expect them to contribute.

Ahhh, I think I see the problem here.  You seem be confusing the term 'expect' with the term 'demand'.

I did ask (first post) and since it's my idea, I do have the right to 'expect' others to contribute if it is to proceed with my participation.  Well, it's obvious by now that they do not want to contribute or even sound in on this conversation, in fact, it appears as I am the only one that wishes to contribute. 

So, my expectations have not been met.  Now I have the right to can it.  Folks can continue to answer the same question(s) over and over again.  I guess it's what gives meaning to their lives.  Even a one trick pony likes to preform.  Sorry if that sounds mean, and it does not apply to all, but it certainly applies to some.
33  Using Arduino / General Electronics / Re: Proposal: Newbie Guide for Electronics on: April 14, 2013, 12:42:59 pm
And herein lies the problem:  To do something like this justice (if you're truly looking to inform a newbie), you have to make sure you refrain from using jargon, or at least when you use jargon you point to where it's defined.

That could be fixed with  a line or 2 of extra explanation to introduce the jargon.  The newbie is going to see that jargon all over the place so it's probably a good thing to use it and explain it.

My 3 examples were not meant to be end product ready, just discussion starters.  I could see additional explanation and simple diagrams/pictures etc... to help make things clearer.

Are YOU willing to do it?"

I am sure that encouraged lot's of people (not).  But I guess if killing creative thought is your thing, then who am I to argue.

In any case, from my perspective, I'd certainly be willing to contribute.  However, I'd expect many of the senior members of this forum to contribute as well.  The last thing I would want to do is spend 20 hours of my time doing up the whole list only to have 50 people's opinions on how to change everything.

A better approach would be have 10 or 20 people volunteer to suggest and take on one to two topics, produce their document for inclusion and and make any reasonable changes before calling it a done deal.

The initial publication could be from 10 to 20 rules, and any additions could be produced by those who feel they need to be added.  One or more global moderators could be the final judges on what makes it in and what does not.
34  Using Arduino / General Electronics / Re: Why are real-time clocks always 32.768khz? on: April 13, 2013, 10:11:21 am
Not sure the loading with 2x18pF (those basically connected in series give you 9pF, plus stray capacitances) will give you good results when the crystal is intended ie. for 6pF, though.

The values I show in my circuit are what worked for me.  Like the link says, you can try  R1=20M, r2=500K and caps between 10 and 20 pF.

I may have had a stubborn crystal, hence the 330K I used, and it's the only thing that really concerns me as these watch crystals do not like too much drive.  However, if it shatters or ages too much, I'll try a new crystal with 500K but will keep everything else the same.
35  Using Arduino / General Electronics / Proposal: Newbie Guide for Electronics on: April 13, 2013, 10:00:26 am
I propose we create a newbie rule guide for this forum that we can make sticky and point beginners to that might help cover 90% of the problems on this site.  A sort of top 20 newbie rules thing.

Here is few examples of what I have in mind.

Rule #1: Always use decoupling capacitors.  At least one decoupling capacitor should be used for each power pin on each IC and be placed as close to the power and ground pins of the IC as possible.  If you have not done this yet, do not post a question on this site.

Rule #2: When connecting signals from two different circuits, you must always make sure adequate ground connections are made between the two circuits.  It is not enough just to connect the signals alone.  Ignoring this rule can cause damage to one or both circuits and will certainly cause 'interesting' behavior.

Rule #3: Always use an adequate power supply.  Make sure you understand the power requirements of your project and use a supply that will easily handle these requirements.  In other words, do not try to run Ethernet interfaces, relays, motors or servos as well as your Arduino off of one of those small 9V rectangular batteries.  It's just not going to work.

Whud'yall thank, huh?
36  Using Arduino / General Electronics / Re: Why are real-time clocks always 32.768khz? on: April 13, 2013, 09:31:27 am
Yes I could do with a diagram suited for a 32.768 KHz crystal and someone previously described one.

You really need clean breadboard techniques for something like this.  Follow dc42's recommendations and make sure your breadboard is making good contact with the wires (no worn contacts, no corroded wires).  You can try the attached circuit.
37  Using Arduino / Microcontrollers / Re: ATmega648P-PU? on: April 12, 2013, 11:47:54 am
That might actually work for one case, but not the rest.  Not sure it would be worth the trouble for the one where it would work though.  We'll give it some thought, thanks.

Can't believe though that others would not be interested in this.  I half expected there would a big response.  After all, there must be multiple millions of Arduinos and compatibles out there.  That woudl reason enough for Atmel to consider adding the chip to their line-up.  However, if no one sees the need, that explains the lack of an ATmega648 I guess.

They aren't going to make one just for little ol' me.
38  Using Arduino / General Electronics / Re: Why are real-time clocks always 32.768khz? on: April 12, 2013, 11:21:50 am
Clock "adjustment":  32768 / 2^15 = 1

Right you are!
39  Using Arduino / General Electronics / Re: Wall Power Supply question on: April 12, 2013, 11:01:36 am
Switching power supplies can be had pretty cheaply these days.  I've used these without trouble.
40  Using Arduino / General Electronics / Re: Why are real-time clocks always 32.768khz? on: April 12, 2013, 10:06:37 am
It is easy to divide that frequency using a binary counter to get 1 second pulses.

32768 / 214  = 1
41  Using Arduino / Microcontrollers / ATmega648P-PU? on: April 11, 2013, 03:25:33 pm
So, what are the chances that Atmel will bring out an ATmega648 or ATmega1288.  Direct drop-in replacements for the 328 and it's kin with 64K or 128K of flash.  Doubling up on the other memory resources would also be cool.

I have a few existing projects that I can no longer expand because of program space limits with the 328.  My only solution as it is is to re-build them with a larger chip.  Not something I'm looking forward to.

Have Atmel ever expressed any appetite for this concept?
42  Using Arduino / General Electronics / Re: Do I really need to solder headers to a shield? Or can I just plug it in? on: April 06, 2013, 08:43:24 am
And So would you say it's better if I just solder all 4?

Yes, solder all 4.  It will give you practice soldering and it will make the whole thing more stable.
43  Using Arduino / Installation & Troubleshooting / Re: Multiple Problems with Arduino Leonardo on: April 06, 2013, 07:57:28 am
i agree wholeheartedly.  The Leonardo is an abomination that was created to solve a problem that never really existed.  Sorry if this sounds harsh but it is how I feel, and I am only stuck with one of them, not 25.  I used mine for about 15 minutes and just gave up.  There was/is absolutely no reason to put up with it's ridiculous behavior.

For your application, there are a lot of great boards around that were specifically designed to be used in a classroom/development environment.  Like this:

I got one and have not looked back.  It is soooo much nicer to deal with for development work than even an Uno or Duemilanove.  The only thing is that it's bigger and not really suitable for embedding in a final project.  Not that I'd do that anyway, but others seem to from time to time.

I know it does not help you now, and I wish I knew a way to do that, but you have my sympathies.  I feel for you.
44  Using Arduino / Microcontrollers / Re: Stand alone programming - should it be this simple ? on: April 05, 2013, 11:45:50 am
I am familiar with that USB to TTL board.  The reset pin on it is actually the pin to reset the CP2102 chip on the board.  I do not know why it is even brought out at all.

You need to find the DTR signal (I think it is pin1 of J2, but the silk screen on the bottom of the board will identify it) and run it through a 0.1 uf capacitor to the reset pin on the ATmega328.  You will also need a 10K pull-up from the reset pin on the 328 to Vcc.
45  Using Arduino / General Electronics / Re: ULN2803A continuous current on: February 23, 2013, 09:40:24 am
I think it's safe to consider the 1.8W and 25C to be mutually exclusive unless liquid cooling is involved. smiley-wink

The datasheet specifies a junction to ambient thermal resistance of 55C/W.  At 25C ambient and 1.8W that would mean a junction temperature of 125C, which is the maximum.

I would also add that most modern LEDs shine very brightly on just less than 5mA.  They last forever that way too.  25mA just leads to short lives.

Who said 25ma?
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