7815

lopan · 13th November 2004, 05:30 AM

If I tie a 15 or 16 volt source to the output pin of an umpowered 7815 and 0 to its ground pin will this damage it. I want to be able to jump back an forth between two supplies -- one on board and the other outboard.

Any thoughts thanks

li_gangyi · 13th November 2004, 02:43 PM

it might damage the IC...u can put a diode across from the input to the output to solve this problem though...

dnsey · 13th November 2004, 03:41 PM

Why do you need to keep the reg o/p connected when the external supply is in use?
Can't you just switch between them, rather than adding the ext. supply?

paulb · 13th November 2004, 04:30 PM

It seems to me that we did some checking once and the 7815 can sink current (it normally sources). It didn't seem to hurt it as long as the current was kept low. So it may work just fine.
They're cheap, so if you blow one up, oh well.
Oh wait, you said unpowered...not sure about that. Try it!

li_gangyi · 14th November 2004, 02:19 AM

u're not suppossed to stick anything after the regulator, and leave the regulator unpowered...check the app note.
www.national.com
the diode thingy I mentioned is in the app note as well

13th November 2004, 05:30 AM	#1
lopan diyAudio Member Join Date: Sep 2004 Location: California	7815 If I tie a 15 or 16 volt source to the output pin of an umpowered 7815 and 0 to its ground pin will this damage it. I want to be able to jump back an forth between two supplies -- one on board and the other outboard. Any thoughts thanks

13th November 2004, 02:43 PM	#2
li_gangyi diyAudio Member Join Date: Jun 2003 Location: Woodlands Circle	it might damage the IC...u can put a diode across from the input to the output to solve this problem though... __________________ Kids in the back seat cause accidents...Accidents in the back seat cause kids...

14th November 2004, 02:19 AM	#5
li_gangyi diyAudio Member Join Date: Jun 2003 Location: Woodlands Circle	u're not suppossed to stick anything after the regulator, and leave the regulator unpowered...check the app note. www.national.com the diode thingy I mentioned is in the app note as well __________________ Kids in the back seat cause accidents...Accidents in the back seat cause kids...

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13th November 2004, 03:41 PM	#3
dnsey diyAudio Member Join Date: Mar 2004 Location: Shropshire, England	Why do you need to keep the reg o/p connected when the external supply is in use? Can't you just switch between them, rather than adding the ext. supply?

13th November 2004, 04:30 PM	#4
paulb diyAudio Member Join Date: Jun 2001 Location: Calgary	It seems to me that we did some checking once and the 7815 can sink current (it normally sources). It didn't seem to hurt it as long as the current was kept low. So it may work just fine. They're cheap, so if you blow one up, oh well. Oh wait, you said unpowered...not sure about that. Try it!

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