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D25 Diode voltage variance ??

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Bill Schlatterer

Joined: 09 Jan 2006
Posts: 195

Posted: Mon Jan 16, 2006 6:46 pm Post subject: D25 Diode voltage variance ??

Anyone?  Wiring per Z13 with Main Bus and E-Bus.  I have the D25 diode

installed between them per diagrams.  Just for fun, I was checking voltage

at the Main Bus which was 12.3 but on the E-Bus (one D25 and 6 inches of

14ga away), it was down to 11.7 volts for a loss of .6 volts.  This seemed

like a lot of voltage loss so I tried another D25 and it read an even 12.0

volts for a loss of .3.  



Now I'm wondering if either of these is normal and if so what is acceptable

loss between the buses?



Thanks Bill S

7a Ark

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ceengland(at)bellsouth.ne
Guest

Posted: Mon Jan 16, 2006 6:53 pm Post subject: D25 Diode voltage variance ??

Bill Schlatterer wrote:



 	  Quote: 	
		  

Anyone?  Wiring per Z13 with Main Bus and E-Bus.  I have the D25 diode

installed between them per diagrams.  Just for fun, I was checking voltage

at the Main Bus which was 12.3 but on the E-Bus (one D25 and 6 inches of

14ga away), it was down to 11.7 volts for a loss of .6 volts.  This seemed

like a lot of voltage loss so I tried another D25 and it read an even 12.0

volts for a loss of .3.  



Now I'm wondering if either of these is normal and if so what is acceptable

loss between the buses?



Thanks Bill S

7a Ark




	


Normal voltage drop across a forward biased silicon diode is ~.6 volts.

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mprather(at)spro.net
Guest

Posted: Mon Jan 16, 2006 7:16 pm Post subject: D25 Diode voltage variance ??

While the voltage drop across vs. current through a diode is not linear,

certain places within the "I-V" curve are nearly so...



http://en.wikipedia.org/wiki/Image:Rectifier_vi_curve.GIF



 - In this application, we are forward biased.



When you say that you measured the voltage drop across each diode, I

assume you were checking this while it was installed in the circuit, and

while the diode was conducting current..  Roughly, was the current through

the diode the same in each case (same number of items connected to the

e-bus)?



To answer your question, 0.3V sounds a little low for a regular Si

rectifier, while 0.6V sounds pretty typical (actually, still a little

low).  I would guess that the diode which showed a 0.3V drop wasn't

carrying much (any) current at the time of the test.

Regards,



Matt-



 	  Quote: 	
		   

 <billschlatterer(at)sbcglobal.net>

 Anyone?  Wiring per Z13 with Main Bus and E-Bus.  I have the D25 diode

 installed between them per diagrams.  Just for fun, I was checking

 voltage at the Main Bus which was 12.3 but on the E-Bus (one D25 and 6

 inches of 14ga away), it was down to 11.7 volts for a loss of .6 volts.

 This seemed like a lot of voltage loss so I tried another D25 and it

 read an even 12.0 volts for a loss of .3.



 Now I'm wondering if either of these is normal and if so what is

 acceptable loss between the buses?



 Thanks Bill S

 7a Ark

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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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BigD(at)DaveMorris.com
Guest

Posted: Mon Jan 16, 2006 7:22 pm Post subject: D25 Diode voltage variance ??

The 0.6V is normal.  Remember when the diode is in the circuit, you're 

running on alternator with something higher than 12.3V, so even with the 

voltage drop, it will be within tolerable limits.  When the alternator is 

offline and you need maximum voltage, you are powering the E-bus through 

the switch, not through the diode, so there will be no voltage drop.



Dave Morris



At 08:45 PM 1/16/2006, you wrote:

 	  Quote: 	
		  

<billschlatterer(at)sbcglobal.net>

Anyone?  Wiring per Z13 with Main Bus and E-Bus.  I have the D25 diode

installed between them per diagrams.  Just for fun, I was checking voltage

at the Main Bus which was 12.3 but on the E-Bus (one D25 and 6 inches of

14ga away), it was down to 11.7 volts for a loss of .6 volts.  This seemed

like a lot of voltage loss so I tried another D25 and it read an even 12.0

volts for a loss of .3.



Now I'm wondering if either of these is normal and if so what is acceptable

loss between the buses?



Thanks Bill S

7a Ark

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Bill Schlatterer

Joined: 09 Jan 2006
Posts: 195

Posted: Mon Jan 16, 2006 7:29 pm Post subject: D25 Diode voltage variance ??

Thanks for the reply! Seemed like a lot but I guess this isn't really

important because in normal ops, the active system keeps it up and in a low

voltage situation, the Main and D25 are out of action anyway and the E-Bus

circuit gets remaining battery power to the E-Bus with little or no loss.  



Thanks Bill S



--

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