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Drawing current from the 5v rail on an arduino

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dr pepper

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So I put together a gps disciplined ad9850 dds system with a lcd, proud of the creation I built a case for it and assembled everything.
Worked for a minute then nada.
Silly me I powered the system from usb while developing it, but on the cased up version powered it from a 9v wall wart, I used 3 x ac logic ic's to divide the 125mc clock down to a freq the 'duino can count, and it looks like I drew too much current with too much voltage diferential across the 'duio's reg.
I found spec for a genuine 'duino 450ma can be pulled from the 5v rail totall, but I cant find anything about the voltage differential.
Any info on this would be great, pkus my arduino's are non original so I spose the rating will be less.
I'm thinking use a 7805 and squirt the regulated dc into the raw 5v pin, and route separate volts to the counter / lcd / ad9850.
Might even try repairing the 'duino.
 

MikeMl

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No heatsink on the regulator except a slightly fatter copper trace, so dissipating more than a few hundred milliWatts in the reg would be a problem...

I have found that you really need about >5.5V going into the Arduino if you really expect the on-board regulator to make a clean 5.0V for the Arduino ADC... I have had a problem getting clean 5.oV if running from the USB. Older Arduinos had a solder jumper to bypass the on-board regulator; newer ones, especially the Chinese clones dont...
 
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dr pepper

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Yep I'm dissipating a little over a watt, so thats probably nuked the reg, the avr and everything else got hot so I suspect the reg might be short, so everything could be shot.
I have a clone with a dip and a few with smd's, the dip one does have said solder link, the smd ones dont, but thats not a major problem I could just pull the reg, I'm going to try that on the one I blew up, and power it from one of the 5v o/p pins, its toast anyway.
 
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