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Author Topic: Can I power arduino with 12 through barrel jack?  (Read 1533 times)
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I have a salvaged power supply brick that supplies 5amps of 12 volt power and the barrel plug happens to fit the arduino uno i have. Can I run the arduino on this 24/7?

I also need to power some solenoids with the 12 volts. Can I pull power out of the Vin pin? I have 8 solenoids that each take 350 mA, which I assume means that at times I might be drawing as much as 2.8 amps (.35 amps * 8 solenoids). Can I draw that much through the Vin pin without anything bad happening?
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I have a salvaged power supply brick that supplies 5amps of 12 volt power and the barrel plug happens to fit the arduino uno i have. Can I run the arduino on this 24/7?

Yes, that would work nicely.

I also need to power some solenoids with the 12 volts. Can I pull power out of the Vin pin? I have 8 solenoids that each take 350 mA, which I assume means that at times I might be drawing as much as 2.8 amps (.35 amps * 8 solenoids). Can I draw that much through the Vin pin without anything bad happening?

Unfortunately no. There is a series polarity protection diode rated at 1 amp current wired between the DC barrel connector and the Vin pin, so that sets the max current draw limit from the Vin pin. You can however splice into the 12vdc cable before the barrel connector to utilize the full current rating of the supply. Be sure to use wire gage size suitable for the maximum current you will be drawing from the supply.

Lefty
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Drat. Well, thanks for the info.

If I splice it, I can just put the power in to Vin and ground pins and it'll run through the voltage regulator, right?
« Last Edit: March 29, 2012, 12:30:50 pm by greengiant83 » Logged

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"If I splice it, I can just put the power in to Vin and ground pins and it'll run through the voltage regulator, right? "
Yes. That bypasses the reverse polarity protection diode. Be careful.

If you splice it, keep the barrel jack going to the arduino (make sure center is positive, and outer shell is Gnd) and take your 'bare' wires over to the solenoids.
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I draw more than 1A all the time from the Vin pin.  But I'm not sure if I did this with my Uno.  I'm positive it works with the Yourduino Aroboto.  Are you certain it's not just between USB power and Vin?  Can you instead power the Uno into the Vin pin instead of the barrel?  This would bypass the diode.  Maybe it can handle 3A for a short while even though it is rated at 1A?  Where would this be on my board so I can see it or feel it when it's hot?  The PCB layout is similar to Uno.
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Measured the current it's 2A for an hour nothing got hot besides the motor.
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Are you certain it's not just between USB power and Vin?
Yes, look at the schematics. It is an M7 diode. That has a maximum forward current specification of 1A.

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Measured the current it's 2A for an hour nothing got hot besides the motor.
It is not just heat that kills a component due to over current, it is things like carrier depletion and thermal stress.
So you diode will die long before it's time is due, because you are over running it by 100%. Not a thing I would recommend.
It's like all the people who smoke and say "well I am not dead yet".
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I'm using a different board.  Maybe it's not an M7 diode.  Where would I find it on a Uno PCB?
Mine is similar layout.
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Where would I find it on a Uno PCB?
On the bottom edge under the two round capacitors between the jack and the pin header on this photograph.
http://arduino.cc/en/Main/ArduinoBoardUno
You can see it says M7 upside down.
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Mine says SS14 also 1A.  But it doesn't get warm at 3A.  I hear you...
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