New to Arduino: Trying to build an Arduino board..

Forum 2005-2010 (read only) Hardware Development
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Hello,

First off, I'd like to say I am very new to Arduino. I know a thing or two about electronics, but to Arduino, not so much.

In the past, I have usually just stayed within my comfort zone and built basic projects that didn't require much effort.

But I'd like to change that. I want to attempt to build my own Arduino board using one of the pre-made Arduino schematics. I have not yet figured out which model I'd like to base it on, but they are all pretty similar.

But before I go picking up all of the parts, I was wondering whether or not Arduino was going to get a refresh anytime soon. I see the last revision was from 2009. I don't care when it was made, I just don't want to finish the thing and then a day later the 2010 version come out...

Besides that, I just have one real question and that is with the power source.

So it wants a 5V input, right? However,on the product page it says it would prefer if it had somewhere from 7-12V input and then have the voltage regulator bring the voltage down. If I was to build my own Arduino, can I just use/build a 5V power supply with ample amperage and loose the 5V regulator on the board?

Is there a reason why the it says it doesn't actually want 5V input but rather something higher? Something to do with that particular board. I plan on building a powerful 5V power supply so perhaps this wouldn't be an issue?

And one more thing regarding the 3.3V rail. I don't have to make a dedicated 3.3V supply, would I? I can just use the power from the 5V...If that makes sense...

Thank you oh so very much.

With gratitude,

-Tim

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the whole date thing is just board revisions, if the arduino bootloader changes you can use your arduino to reflash the chip

and you can use a 5v supply, as long as its regulated

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Thank you for the quick reply. By revisions I mean changes to the architecture and maybe even the microcontroller. But I guess there is really no need for any of that at the moment.

What is the reason they recommend 7V+ input? Things like batteries than loose voltage over time sort of thing? Alkaline starts at 1.5V but quickly dips down to about 1.2V and EOL, they are close to 1V.

Is that why?

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The 7V+ input is so that it can be regulated down to 5V on the board. You can build your own +5V supply and provide power that way but it has to be a regulated +5V supply, whereas the 7V+ input can be unregulated, which is common for things like wall transformers and, as you mention, batteries.

And yes, you can derive your own +3.3V supply from the +5V supply.

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Thank you. You have helped me alot.

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And one more question if I may...I was going to use a RS-232 to USB board from Sparkfun which is good but it means I'll keep on having to buy $15 conversion boards for every unit I make, or anything else somewhere down the line.

Can arduino connect to a computer by means of RS-232 directly? Does it have to use USB or is that just for convenience. I have an old Serial/RS-232 card from an old computer and am thinking of just plopping that in my new one, and in turn I won't have to spend a dime on conversion boards....

But I was just trying to figure this out. It seems most people with the standard Duemilanove or Mega or any of them, use a USB connection and probably because RS-232 has been phased out...Is it just a convenience thing?

Thanks.

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It is convenience and, as you noted, RS232 is being phased out. It is difficult to find a (laptop) computer that comes with an RS232 port anymore. If you have an RS232 card there's no reason you can't use it with the AVR.

You will need a level converter like a MAX232 to convert the 0V/5V serial signals from the AVR to the +10V/-10V signals expected by your RS232 card.

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arduino does not use RS232, rs232 is 1 = -12v 0 = +12 v, so you need some form of converter & inverter, which honestly could be a couple transistors and some other minor passive parts (i use mine on a real serial port, and like a 6$ adapter from modern device)

the usb part is mainly for modern convenience

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Oh I completely forgot about the voltage differential. Making a MAX232 seems simple enough. A few capacitors, MAX232 chip, and RS-232 port.

Well thank you very much for all of the assistance. It's greatly appreciated.

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I wouldn't bother converting RS232 to 5v, FTDI make serial bridge cables that have the USB bridge chip built into the cable, one of them has a 6-way connector with the DTR ans RTS signals brought out so presumably the auto reset on the Arduino will still work.

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Well either way. I can still just get myself an FTDI breakout board or cable if something doesn't work out.

Regarding the ATMega chips as well. The only foreseeable difference I see between an ATMega168 and an ATMega 1280 is onboard capacities and ROM/RAM/Flash etc. sizes.

If I had a schematic that wanted to use an ATMega168/328, can I simply use a 1280 in its place? Or is that a no-no? They appear to be the same architecture, and 1280s are official Arduino chips.

Thanks.

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Whoops. I take that back. There are a whole lot more pins on the 1280 than on a 328. I must be blind.