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Author Topic: arduino BT output current  (Read 668 times)
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How much current can you draw from the arduino BT board? Is the DC-DC converter powerful enough to switch on LED's on all pins? Can you attach some peripherals to the 5V connection? Is there any use for the +9V pin?

I haven't seen a lot questions about this new board. Did I miss a page with info? (again)


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Daniel
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OOPS: see later post.


hi

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How much current can you draw from the arduino BT board?

Most of the answer to this is in the Atmega8 data sheet. The pins are rated for up to 40ma, but for stable designs you should stay around 20ma max, as the output voltage drops rapidly after 20ma. The chip also has an overal current dissipation number (300 MA max throught the Vccpin)  that you have to stay under.

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Is the DC-DC converter powerful enough to switch on LED's on all pins?
The regulator provides 500 ma maximum to the entire board. There is about 400 ma of that available for user aplications.

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Can you attach some peripherals to the 5V connection? Is there any use for the +9V pin?
you can attach whatever you want to those pins, bearing in mind that the 5V suply is limited as above.


Hope this helps

D
« Last Edit: February 10, 2007, 02:35:15 pm by Daniel » Logged

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The regulator provides 500 ma maximum to the entire board. There is about 400 ma of that available for user aplications.  


Great, much more than I expected. And I was afraid that I couldn't even connect a few LED's.

Thanks.
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Daniel
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Oops... I thought you meant a regular Arduino.

The BT is different, so you can disregard what I said about regulators above.
The Atmega chip specs should be the same.


I have a few BT's here, and here is what I can tell you:

TheDC-DC converter in the Arduino BT is a really really really teensy-weensy MAX 1676-EUB. It puts out  300ma "typical", but maybe more, as the spec sheet says it has adjustable limiting, and we don't yet know how it has been 'adjusted' in hardware. I would guess 500ma.

The BT takes 1.5 to 5.5V as supply voltage. You can go down to .7V or so, according to the spec sheet for the converter.
Going over 5.5V will destroy the board.

There is a low-battery LED.

There is some kind of clamping diode on the input, but irregardless of this, apparently the board will die if you connect the power backwards.  

The Arduino "9V" pin is actualy conected to the +  battery supply. My half-dead batteries measure about 2.2V on that pin right now.  

So, no 9V supply, just 5V at about 150ma(? after the BT module uses a bunch of juice) or so available for your circuits.

The good news is that the battery life is terrific with two AA batteries. (The radio range is also amazing, much farther than I would have imagined.) I have been running the same unit intermittently for several days on two AA Duracells.  The converter will take every drop the batteries have to give, since it wil run down to very low voltages.

D
« Last Edit: February 10, 2007, 04:22:59 pm by Daniel » Logged

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Well, 150 mA should do it. For now I am only thinking about a GPS, some memory and maybe some indicator LED's. The GPS takes 70 mA, that leaves 80 mA.

I have read some different things about the range. At tinker.it, http://tinker.it/now/2007/01/13/the-arduino-bluetooth-board/ I read it would work to a distance of 100 m.
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