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E-Bus and switching

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PaulR

Joined: 13 Nov 2008
Posts: 22
Location: Alabama

Posted: Fri Jan 16, 2009 8:36 am Post subject: E-Bus and switching

I'm in the process of plagerizing Bob's Z-11 for my VFR 9A and have a question for the group.  I'm pretty new to this wiring business so please be gentle.  I've done the search thing to no avail.



Is there a reason that the e-bus couldn't be powered through a switch like a 1-3 with power from either the main bus or the always hot bus feeding the e-bus?  This would negate the need for the diode, I think.



I'm sure this has been asked before, but I couldn't find a reference to it.



For what it's worth, I really enjoy learning about this part of the build and this is the best place I've found for that.



Thanks

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_________________
Paul Rose
N417PR
RV-9A

jaybannist(at)cs.com
Guest

Posted: Fri Jan 16, 2009 9:32 am Post subject: E-Bus and switching

 	  Quote: 	
		  Paul,



I'm not an expert in airplane electronics, but I’m sure you can do almost anything 

you want with switches.  I have a toy train setup for the grandkids that has four 

track switches. I can set the track up to do some pretty complex  routes.  

In order to make the train do what the kids want, I can stop the train, figure 

out how to set the switches, set them and run the train to see if I guessed right.  



Your endurance bus could be more properly called an emergency bus.  Do you want 

to go through a switch puzzle routine during an emergency? Remember that you 

can’t just “stop the train” long enough to do an analysis. When  things go haywire, 

the diode arrangement allows you to get that e-bus on line and prevent back-feeding 

the main bus by flipping only one switch.  You can’t get much simpler than that. 



I recommend that you stay with an arrangement that Bob has proven to be workable,

 simple and reliable.



Jay in Dallas 

	


   

 

   

 

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PaulR

Joined: 13 Nov 2008
Posts: 22
Location: Alabama

Posted: Fri Jan 16, 2009 11:14 am Post subject: Re: E-Bus and switching

Jay,

I appreciate your answer, but if I'm reading the Z-11 diagram correctly,

when I switch the master contactor off to reduce the load, I still have to flip a switch to turn the alternate power on to the e-bus.  What I'm suggesting is that switch that gets moved after shutting down the master is simply a switch to change where the power comes from. Single Pole double throw, I believe is the terminology.

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_________________
Paul Rose
N417PR
RV-9A

jaybannist(at)cs.com
Guest

Posted: Fri Jan 16, 2009 12:04 pm Post subject: E-Bus and switching

Paul,

 

 As I said before, I am not an expert in these things, but here is my take on it:  If you have a need to activate the e-bus, I would assume that something in the main bus system had gone wrong, possibly already de-energizing the contactor.  It could be a blown crowbar or even failure of the master switch. The second switch eliminates that single point of failure.  The first action would be to flip the e-bus switch, then decide if you need to turn the master off.  I would hesitate to combine an emergency switch with one that might be involved in whatever problem is occuring. 

 

 Jay in Dallas

 

   

 

   

 

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gyoung

Joined: 09 Jan 2006
Posts: 211
Location: Republic of Texas

Posted: Fri Jan 16, 2009 1:03 pm Post subject: E-Bus and switching

The diode allows the e-bus to get power from both the main and aux batteries

and prevent backfeeding the aux battery to the main bus. The e-bus switch

controls the feed from the aux battery to the e-bus and is limited to

something like 8-10 amps that a switch can easily handle. If you replace the

diode with a crossfeed switch, it will need to stay closed to allow main

power to feed the e-bus. If you also have the e-bus switch closed a failure

in the main battery/bus would start sucking power from the aux battery. If

you don't notice it fast enough you could drain the aux battery. If the

e-bus switch is open instead, then the ebus will lose power until you kill

the master, kill the crossfeed and close the e-bus switch. With the diode

all the critical stuff on the e-bus maintains power without forcing you to

take the right actions, in the right sequence at the right time. Why break a

sweat when a <$30 diode prevents it?



Regards,

Greg Young

 



[quote] --

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khorton01(at)rogers.com
Guest

Posted: Fri Jan 16, 2009 6:06 pm Post subject: E-Bus and switching

On 16-Jan-09, at 11:36 , PaulR wrote:



 	  Quote: 	
		   

 >



 I'm in the process of plagerizing Bob's Z-11 for my VFR 9A and have  

 a question for the group.  I'm pretty new to this wiring business so  

 please be gentle.  I've done the search thing to no avail.



 Is there a reason that the e-bus couldn't be powered through a  

 switch like a 1-3 with power from either the main bus or the always  

 hot bus feeding the e-bus?  This would negate the need for the  

 diode, I think.


	




I suspect that this switch would remove main bus power before it  

supplied the hot bus power.  Thus the e-bus would lose power during  

the transition, which would cause any devices powered from that bus to  

reboot.  That may or may not be important, depending on exactly what  

you have on that bus.



--

Kevin Horton         RV-8 (Grounded)

Ottawa, Canada

http://www.kilohotel.com/rv8

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khorton01(at)rogers.com
Guest

Posted: Fri Jan 16, 2009 6:07 pm Post subject: E-Bus and switching

On 16-Jan-09, at 21:03 , Kevin Horton wrote:



 	  Quote: 	
		   On 16-Jan-09, at 11:36 , PaulR wrote:



> 

> >

>

> I'm in the process of plagerizing Bob's Z-11 for my VFR 9A and have  

> a question for the group.  I'm pretty new to this wiring business  

> so please be gentle.  I've done the search thing to no avail.

>

> Is there a reason that the e-bus couldn't be powered through a  

> switch like a 1-3 with power from either the main bus or the always  

> hot bus feeding the e-bus?  This would negate the need for the  

> diode, I think.

 I suspect that this switch would remove main bus power before it  

 supplied the hot bus power.  Thus the e-bus would lose power during  

 the transition, which would cause any devices powered from that bus  

 to reboot.  That may or may not be important, depending on exactly  

 what you have on that bus.


	




Drat - I hit Send too soon.



Also, this arrangement makes the switch a single failure that can kill  

all power sources to the e-bus.  This may or may not be a problem,  

depending on the consequences of losing all items on the e-bus.

--

Kevin Horton

Ottawa, Canada

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nuckolls.bob(at)aeroelect
Guest

Posted: Fri Jan 16, 2009 8:52 pm Post subject: E-Bus and switching

At 01:14 PM 1/16/2009, you wrote:

 	  Quote: 	
		  



Jay,

I appreciate your answer, but if I'm reading the Z-11 diagram correctly,

when I switch the master contactor off to reduce the load, I still 

have to flip a switch to turn the alternate power on to the 

e-bus.  What I'm suggesting is that switch that gets moved after 

shutting down the master is simply a switch to change where the 

power comes from. Single Pole double throw, I believe is the terminology.


	


   Sources for the endurance bus was crafted

   so that no single failure (like the single spdt

   switch) would deprive the e-bus of power . . .

   and no single component failure has multiple

   effects on system performance.



   Some folks have wired as you've suggested . . .

   but there IS a reason for the architecture as

   published. It's your airplane.

        Bob . . .



        ----------------------------------------)

        ( . . .  a long habit of not thinking   )

        ( a thing wrong, gives it a superficial )

        ( appearance of being right . . .       )

        (                                       )

        (                  -Thomas Paine 1776-  )

        ----------------------------------------

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