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Isolated DC-DC Electronics design pointers

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zk-vii(at)rvproject.gen.n
Guest

Posted: Mon Jun 04, 2007 3:56 pm Post subject: Isolated DC-DC Electronics design pointers

Hi,



I would like to fabricate a small PCB to provide an isolated (or two

isolated) 9V DC supplies (< 250mA each) from the ship 12/14V feed.



I'm happy with designing the PCBs layout / fabrication etc from a schematic

but have been struggling to find a simple solution.  My gut feeling is there

should be a IC out there that does this for me with a few additional

external components - any suggestions?



Thanks,



Carl

--

ZK-VII - RV 7A QB - finishing? - New Zealand

http://www.rvproject.gen.nz/

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aadamson(at)highrf.com
Guest

Posted: Mon Jun 04, 2007 4:13 pm Post subject: Isolated DC-DC Electronics design pointers

Don't they make 7809's?  A single part, maybe need a cap or resistor to

current limit it, but pretty sure they are avail.  Look for LM7809 as a

start, probably all kinds of versions.



Alan 



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hooverra(at)verizon.net
Guest

Posted: Mon Jun 04, 2007 5:01 pm Post subject: Isolated DC-DC Electronics design pointers

Carl,

    Try this NDY1209C A couple of capacitors and you have an isolated 

supply. I have a couple of the 200ma (NDL1209SC) versions for my ANR 

power but I have not yet tested everything although the power supplies 

are working fine. I wired them on a piece of perf board.



Purchased  from:   www.mouser.com

C&D Web site:  http://store.cd4power.com



C&D Technologies, Inc.

11 Cabot Boulevard, Mansfield, MA 02048-1151, USA

Tel: + (508) 339-3000

Fax: +(800) 233-2765

email: sales(at)cdtechno.com

-- 

Ralph C. Hoover

RV7A 

hooverra at verizon dot net

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zk-vii(at)rvproject.gen.n
Guest

Posted: Mon Jun 04, 2007 5:13 pm Post subject: Isolated DC-DC Electronics design pointers

My (limited) understanding is these are similar to the LM315 / 350 type

devices - 3 legged and don't use an isolated ground.



Cheers,



Carl



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jgarner(at)dslextreme.com
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Posted: Mon Jun 04, 2007 5:43 pm Post subject: Isolated DC-DC Electronics design pointers

Hard to beat one or two of these at ~$13 ea...



Dont know if you can get them in NZ though?



HTH, Joe



http://www.digikey.com/scripts/DkSearch/dksus.dll?Detail?Ref=184688&Row 4103&Site=US



Carl Morgan wrote:

 	  Quote: 	
		   

 

 Hi,

 

 I would like to fabricate a small PCB to provide an isolated (or two

 isolated) 9V DC supplies (< 250mA each) from the ship 12/14V feed.

 

 I'm happy with designing the PCBs layout / fabrication etc from a schematic

 but have been struggling to find a simple solution.  My gut feeling is there

 should be a IC out there that does this for me with a few additional

 external components - any suggestions?

 

 Thanks,

 

 Carl

 --

 ZK-VII - RV 7A QB - finishing? - New Zealand

 http://www.rvproject.gen.nz/

- The Matronics AeroElectric-List Email Forum -

Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

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retasker(at)optonline.net
Guest

Posted: Mon Jun 04, 2007 6:22 pm Post subject: Isolated DC-DC Electronics design pointers

Do you actually need isolated 9V?  If so, then the solution suggested by 

Mr. Hoover should be okay.  But note carefully that those devices have a 

minimum load (25% or 83mA for the one in question).  Specifically what 

happens under that load is not specified, but they do say that the 

ripple increases significantly.  Maybe Mr. Hoover can tell us what 

happens at very low or no loads as he has some of these units (assuming 

he has access to an oscilloscope).



If you do not need isolation, then the other suggestion of using a 7809 

is a good one.  This part needs only a small input and a small output 

capacitor (similar to the NDY1209C but can use a lower quality cap).  

They are available from many manufacturers and are very cheap.  The 

NDY1209C specifies 78% efficiency at full load which is not bad but 

probably falls at lighter loads.  The 7809 will run at 63% efficiency 

for all loads (14.2V in and 9V out).  While the difference between 78% 

and 63% may seem like a lot to some, and for high power applications it 

would be, for this application the difference is only 1/2W.  You might 

need a small heat sink on the 7809 depending on what your actual load is.



Dick Tasker



Carl Morgan wrote:



 	  Quote: 	
		  



Hi,



I would like to fabricate a small PCB to provide an isolated (or two

isolated) 9V DC supplies (< 250mA each) from the ship 12/14V feed.



I'm happy with designing the PCBs layout / fabrication etc from a schematic

but have been struggling to find a simple solution.  My gut feeling is there

should be a IC out there that does this for me with a few additional

external components - any suggestions?



Thanks,



Carl

--

ZK-VII - RV 7A QB - finishing? - New Zealand

http://www.rvproject.gen.nz/

  




	


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hooverra(at)verizon.net
Guest

Posted: Wed Jun 06, 2007 7:22 pm Post subject: Isolated DC-DC Electronics design pointers

I have attached a schematic and photo's of the 9VDC ANR supply I 

have built for my RV7A (Headsets Inc ANR conversion) I have tested the 

supply for basic DC voltage. I added a load of about 60ma. The ripple 

looked OK (I do not remember the exact numbers) I will measure again 

when it is wired into the plane and running the Headphones. The Headsets 

Inc. modules draw about 15ma in a quiet shop rising to about 20ma if I 

yell. (Don't know what the neighbors thought!)

    I'll report the final results when everything is powered up and 

operating. The focus now is on getting the panel wiring finished so the 

final skin can go on.

    Getting close!!



-- 

Ralph C. Hoover

RV7A 

hooverra at verizon dot net

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