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Author Topic: Would this fry my Arduinos?  (Read 829 times)
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Hi, I would like three different arduino boards to all power on at the same time at the flick of a switch. I would also like each to have its own 9v battery. If I were to wire it like this, would it fry my boards?

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Switch on the low side.
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If I were to wire it like this, would it fry my boards?
No not as such, but then you have to watch what you are connecting to the arduinos and how they are powered.
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A little confused.... I want to power each with a 9V battery. 2 of the arduinos have LEDs and the third has an adafruit waveshield. Would that work? Im terrified to connect them like this, power it on, and have it wreck the waveshield.

Also, does it make a difference putting the switch on the + or - side of things?
« Last Edit: October 06, 2012, 03:30:10 pm by jeffd » Logged

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I would counter that safe or not, those small 9 volt batteries are really a very poor choice to power an arduino board. They have very little current capacity and as such cost more then nearly any other type of battery choice you could make. And if you don't require portablity then you really should be looking for inexpensive wall wart power modules to power your board(s) over using batteries at all.

Lefty
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Has to be portable, its for a music box. The current is cut as soon as the lid is shut so the circuits will never be on for long periods of time. 9Vs should do the job just fine, but I needed to know if this wiring will achieve what I'm trying to accomplish here.
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Has to be portable, its for a music box. The current is cut as soon as the lid is shut so the circuits will never be on for long periods of time. 9Vs should do the job just fine, but I needed to know if this wiring will achieve what I'm trying to accomplish here.

Well if I was going to do it that way, I would common all the battery negatives together and have the switch break the common ground going to each of the arduino boards, then run seperate positive wires from each battery positive to each arduino Vin pin.

Lefty
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Ok, but the mA of the combined batteries wont be too much? Its my understanding that voltage will stay at 9V because they are in parallel?

Just for educational purposes (im still learning), whats the advantage of having the switch on the common ground rather than a common + ?
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Ok, but the mA of the combined batteries wont be too much? Its my understanding that voltage will stay at 9V because they are in parallel?

No they are not operating in parallel mode, because each board has a seperate wire going to just one positive terminal of one battery. Your arrangement is just allowing one switch contact to turn on or off all three boards at the same time. If you want the batteries to operate in true parallel then all positive terminals should wired together and all negative terminals should be wired together. Then have one wire from these positive terminals to one side of the switch, and then have three wires from the other side of the switch to each of the individual arduino Vin pins. That way the batteries will discharge as one larger battery rather then each discharging at a different rate depending on each specific board and it's shields and external circuitry. 

Just for educational purposes (im still learning), whats the advantage of having the switch on the common ground rather than a common + ?

No advantage, but same effect of single switch turns all on and off, also not true parallel operation, do as above instead.
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Gotcha, thanks!
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Hmmm...
"Danged if that doesn't just fry my arduinos."
"Man, that $#@% really fries my arduinos."
"Dude, your arduinos are fried now."


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