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Topic: is 12V safe for my project? (Read 1 time) previous topic - next topic

I have searched a lot on the forums and there are different opinions to what should I do in my case.

I have to power 12V  0.6A stepper motor. I`m using 12V 1.6A battery pack. I have an arduino shield that drives the motor. Everything is fine, but the voltage regulator gets hot after a while. I know 12V is the upper limit for the arduino, so I`m asking if it's safe to run it like that?  I got suggestion to use a switching regulator for the arduino board but I would rather not if what I have now is safe enough and not burn the voltage regulator. Thanks!

cr0sh

Well - in theory it is; personally, I don't think the heat sinking of the regulator on board the Arduino is sufficient for running it at 12 volts (if it had a proper heat sink attached, it would be OK). Supposedly, though, there is supposed to be enough copper on the board to handle it; I would probably only "trust" it (with reservations) on a real Arduino or a well designed clone (but not on a cheapo Ebay chinese Arduino - who knows on those). If you must run the Arduino off the same 12V source, I would set up an external 5V regulator (7805 - remember to add the capacitors needed to prevent oscillation) and bolt a proper heatsink on it, then feed the output of this into the +5V DC input pin on the Arduino (after verifying the voltage output of the regulator, of course) - which would bypass the on-board regulator.
I will not respond to Arduino help PM's from random forum users; if you have such a question, start a new topic thread.

MarkT

So long as you aren't pushing too much current through the onboard regulator (other than the 328 itself) it should be OK - even if its too hot to touch its well within the safe operating area - regulators shutdown automatically if over-current or over temperature.

However running chips very hot does lead to a lowering of long-term reliability due to thermal stresses at switch on and switch off - especially with plastic packages.
[ I won't respond to messages, use the forum please ]

I see. Thanks a lot for the replies!

So I tried running it for half an hour and after 10-15 minutes the voltage regulator turned off..... Now I`m thinking of getting this voltage regulator
http://www.robotshop.com/dimension-engineering-de-swadj.html
("Output voltage adjusted via a small potentiometer (1.25 to 13V), 1.5A")
It's little pricey, but it comes with capacitors and heat sink so I don't have to bother assembling them and I can use it for other projects as it's adjustable.
Can it help in my case ?
Thanks!

Grumpy_Mike

Yes switching regulators are very efficient and don't burn off excess power so they run a lot cooler.
However you say:-
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I have to power 12V  0.6A stepper motor.

Is that 0.6A in total or per winding?
If it is per winding then you need to feed it with 1.2A and at 12V this is 14.4 watts, this is more than that unit can supply.

Hm... I just checked. It's this one:
http://www.robotshop.com/rbsoy07-soyo-unipolar-stepper-motor.html

So I have been mistaken it's actually 0.4A.

Grumpy_Mike

So that is per phase, therefore in total need  0.8A. At 12V this is 9.6W so it is very close to the limit of what that regulator can give.

yeah :\ I don't know. Do you think I should go this route or just change the motor and battery ? Or there is another variant - get additional 5V power for the arduino only and power the motor shield with the 12V battery.. Which way would you reccomend ?

Grumpy_Mike

I would power the motor from 12V and use this regulator to just power the arduino. Set it to 7V and feed it to the Vin pin, that way your arduino regulator will not get hot.


gravelbar

For what it's worth I've powered Duemilanove's, Uno's, and Pro's at 12v with several hundred hours on all of them with no problems.  I've never checked for heating, though.

Grumpy_Mike

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I've never checked for heating, though.

The main thing that makes electronics die early is excessive heat. Approximately for every 10oC hotter a thing runs the life time of that thing half's.

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several hundred hours on all of them with no problems

You won't see any problems until it suddenly fails.

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