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Contacter, or not?

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heisan

Joined: 19 May 2008
Posts: 22

Posted: Wed Jul 15, 2009 11:42 am Post subject: Contacter, or not?

After all the great info and advice I got on the fuses, I thought I would try asking about contacters too   .



The aircraft manufacturer, and the engine manual both give a wiring diagram that does NOT include a master contacter. The battery positive goes directly to a master switch, and then to the main bus.



This is the first time I have seen a configuration like this (without the contacter).  What are the advantages, and disadvantages of doing it this way?  My maximum current draw is around 10A, so well within the continuous current range of a small toggle switch.



Thanks!

Justin

frank.hinde(at)hp.com
Guest

Posted: Wed Jul 15, 2009 11:57 am Post subject: Contacter, or not?

Where does the starter current go?..Usually it goes through the master contactor..You won't be sending that kind of current through a normal toggle switch..well more than once anyway... 



--

heisan

Joined: 19 May 2008
Posts: 22

Posted: Wed Jul 15, 2009 12:03 pm Post subject: Re: Contacter, or not?

 	  frank.hinde(at)hp.com wrote: 	
		  Where does the starter current go?..Usually it goes through the master contactor..You won't be sending that kind of current through a normal toggle switch..well more than once anyway... 



-- 	




Ah - forgot to mention - the starter has a built in solenoid.

frank.hinde(at)hp.com
Guest

Posted: Wed Jul 15, 2009 12:39 pm Post subject: Contacter, or not?

So there is a separate cable that comes directly from the battery and goes to the starter solenoid..I.e bypasses the switch?



The reason I ask is cus useually the starter cable goes through the master contactor, then through the starter contactor then to the starter.



I.e the starter cable usually goes through the master...At least on "Proper" airplanes..



Sounds like you have an automotive setup?..You could also have a starter solenoid with this setup if you are uncomfortable with the starter cable being permanently hot.



--

mprather(at)spro.net
Guest

Posted: Wed Jul 15, 2009 12:41 pm Post subject: Contacter, or not?

With a peak current demand of 10A, I think you have a few options..



 - Use a small(er) relay mounted close (6") to the battery.  Mount your

distribution bus anywhere you wish.  This is basically a scaled-down

version of existing architectures and provides all of the normal Z

functionality.  This is how my hand-started Varieze is setup.



 - If your battery is located close to the pilot's seat, you may be able

to replace the battery relay with a manually operated battery switch. 

Cable operated switches have been discussed here in the past.



 - Use a battery bus mounted close to the battery.  This is fine if you

don't care about being able to make the whole system "cold" with one

switch.



 - Use an appropriately sized inline fuse to feed the battery to a bus

which is located elsewhere in the plane.  This is probably OK if none of

the electrical equipment is "critical to continued flight"..  Faulting

the fat feeder would cause it's protection to open up, causing all your

electrical stuff to go dark.



Using a relay of any type (esp a fat contactor) causes an extra load on

the electrical system.  If your sole source of power is a small PM dynamo,

every watt starts to add up.  Small relays only draw on the order of 100mA

- less than 1% of the B&C dynamo on my O-200 - an acceptable load..

Regards,



Matt-

 	  Quote: 	
		   

<justin(at)expertron.co.za>
	


 	  Quote: 	
		  

 After all the great info and advice I got on the fuses, I thought I

would
	


 	  Quote: 	
		   try asking about contacters too  [Wink] .



 The aircraft manufacturer, and the engine manual both give a wiring

diagram that does NOT include a master contacter. The battery positive
	


goes directly to a master switch, and then to the main bus.

 	  Quote: 	
		  

 This is the first time I have seen a configuration like this (without

the
	


 	  Quote: 	
		   contacter).  What are the advantages, and disadvantages of doing it this

way?  My maximum current draw is around 10A, so well within the
	


continuous

 	  Quote: 	
		   current range of a small toggle switch.



 Thanks!

 Justin





 Read this topic online here:



 http://forums.matronics.com/viewtopic.php?p 53209#253209

mprather(at)spro.net
Guest

Posted: Wed Jul 15, 2009 12:41 pm Post subject: Contacter, or not?

If your battery is located any significant distance from your starter, you

need a heavy relay or heavy switch..  It's bad practice to have a long

unprotected cable in the airplane which can't otherwise be made cold (via

a switch or contactor).

Regards,



Matt-



 	  Quote: 	
		   

 frank.hinde(at)hp.com wrote:

> Where does the starter current go?..Usually it goes through the master

> contactor..You won't be sending that kind of current through a normal

> toggle switch..well more than once anyway...

>

> --

 Ah - forgot to mention - the starter has a built in solenoid.





 Read this topic online here:



 http://forums.matronics.com/viewtopic.php?p 53216#253216

phil(at)petrasoft.net
Guest

Posted: Wed Jul 15, 2009 12:50 pm Post subject: Contacter, or not?

For only 10 Amps go with the switch.  It takes almost an amp of  

current to hold the master contactor closed so you'd be using ~10% of  

your power just to keep the power on.



One advantage to a master contactor is that the big fat wire that  

doesn't have a fuse on it can be very short.  You can replicate this  

for 10A with an automotive relay near the battery and a small wire  

coming back to the switch, but that is one more thing that can fail.



If it were me, I'd probably just put a fusible link near the battery,  

then run the wire from that to the switch and then to the main buss.   

Simple is good!

Phil Birkelbach

Houston RV7 - 727WB

phil(at)petrasoft.net

http://www.myrv7.com/



On Jul 15, 2009, at 2:42 PM, heisan wrote:



 	  Quote: 	
		   

 >



 After all the great info and advice I got on the fuses, I thought I  

 would try asking about contacters too  [Wink] .



 The aircraft manufacturer, and the engine manual both give a wiring  

 diagram that does NOT include a master contacter. The battery  

 positive goes directly to a master switch, and then to the main bus.



 This is the first time I have seen a configuration like this  

 (without the contacter).  What are the advantages, and disadvantages  

 of doing it this way?  My maximum current draw is around 10A, so  

 well within the continuous current range of a small toggle switch.



 Thanks!

 Justin





 Read this topic online here:



 http://forums.matronics.com/viewtopic.php?p 53209#253209

heisan

Joined: 19 May 2008
Posts: 22

Posted: Wed Jul 15, 2009 1:13 pm Post subject: Re: Contacter, or not?

The battery is mounted around 12"  from the starter, and 20" from the panel.  All 'heavy' current wires are fairly short.



I really like the idea of making it as simple as possible. Added complexity just means extra failure points.



I will definitely go for a fusible link and a switch.



Thanks for the info.



Justin

nuckolls.bob(at)aeroelect
Guest

Posted: Wed Jul 15, 2009 3:21 pm Post subject: Contacter, or not?

At 02:42 PM 7/15/2009, you wrote:

  	  Quote: 	
		  --> AeroElectric-List message posted by: "heisan" <justin(at)expertron.co.za>



 After all the great info and advice I got on the fuses, I thought I would try asking about contacters too  [Wink] .



 The aircraft manufacturer, and the engine manual both give a wiring diagram that does NOT include a master contacter. The battery positive goes directly to a master switch, and then to the main bus.



 This is the first time I have seen a configuration like this (without the contacter).  What are the advantages, and disadvantages of doing it this way?  My maximum current draw is around 10A, so well within the continuous current range of a small toggle switch. 	


    The legacy design goal for a battery master

    disconnect is to provide a means by which nearly

    all wiring in the airplane is 'cold' when the 

    disconnect is open. If the battery is conveniently

    located then some form of manual switch can be

    considered. Perhaps like this?



 [img]cid:.0[/img]

 [img]cid:.1[/img]



    The next reason for a battery master disconnect is

    to provide a means by which the battery can be

    shut off if the starter contactor (solenoid)

    sticks.



    If the battery master cannot positioned conveniently

    for manual operation, then perhaps a contactor is

    indicated. These can be low power devices like the

    EV series devices from TYCO . . . but it's pretty

    easy to make an el-cheeso contactor emulate the

    low power characteristics of the TYCO device.



    Finally, a couple of guys on the list were working

    on versions of remotely controlled, manual switches

    like this:



  http://aeroelectric.com/Catalog/AEC/9042/9042-100.pdf



    In any case, there's two good reasons for a battery

    master disconnect. The style is up to you as is

    the choice for installing one.



 

        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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mprather(at)spro.net
Guest

Posted: Wed Jul 15, 2009 3:52 pm Post subject: Contacter, or not?

Bob,



Your comments gave me another idea..  If you only have 12-14A to play with

(little dynamo), and the airplane has a starter..  And your normal running

power budget is a fairly high percentage of the output of the dynamo.. 

One could install a battery contactor (or starter relay) just for running

the starter - in series with any starter/engine mounted relay/solenoid. 

Once the engine is running, the current draw from the monster contactor

can be eliminated and you can drop back to a more power-frugal relay for

driving the rest of the electronics on the airplane - a relay installed in

parallel.  I can't think of any downside.

Regards,



Matt-



 	  Quote: 	
		   At 02:42 PM 7/15/2009, you wrote:

>

> <justin(at)expertron.co.za>

>

>After all the great info and advice I got on the fuses, I thought I

>would try asking about contacters too  [Wink] .

>

>The aircraft manufacturer, and the engine manual both give a wiring

>diagram that does NOT include a master contacter. The battery

>positive goes directly to a master switch, and then to the main bus.

>

>This is the first time I have seen a configuration like this

>(without the contacter).  What are the advantages, and disadvantages

>of doing it this way?  My maximum current draw is around 10A, so

>well within the continuous current range of a small toggle switch.



     The legacy design goal for a battery master

     disconnect is to provide a means by which nearly

     all wiring in the airplane is 'cold' when the

     disconnect is open. If the battery is conveniently

     located then some form of manual switch can be

     considered. Perhaps like this?



 Emacs!



 Emacs!

     The next reason for a battery master disconnect is

     to provide a means by which the battery can be

     shut off if the starter contactor (solenoid)

     sticks.



     If the battery master cannot positioned conveniently

     for manual operation, then perhaps a contactor is

     indicated. These can be low power devices like the

     EV series devices from TYCO . . . but it's pretty

     easy to make an el-cheeso contactor emulate the

     low power characteristics of the TYCO device.



     Finally, a couple of guys on the list were working

     on versions of remotely controlled, manual switches

     like this:



 http://aeroelectric.com/Catalog/AEC/9042/9042-100.pdf



     In any case, there's two good reasons for a battery

     master disconnect. The style is up to you as is

     the choice for installing one.

         Bob . . .



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

         ( . . .  a long habit of not thinking   )

         ( a thing wrong, gives it a superficial )

         ( appearance of being right . . .       )

         (                                       )

         (                  -Thomas Paine 1776-  )

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

nuckolls.bob(at)aeroelect
Guest

Posted: Thu Jul 16, 2009 7:11 am Post subject: Contacter, or not?

At 06:50 PM 7/15/2009, you wrote:

 	  Quote: 	
		  



Bob,



Your comments gave me another idea..  If you only have 12-14A to play with

(little dynamo), and the airplane has a starter..  And your normal running

power budget is a fairly high percentage of the output of the dynamo..

One could install a battery contactor (or starter relay) just for running

the starter - in series with any starter/engine mounted relay/solenoid.

Once the engine is running, the current draw from the monster contactor

can be eliminated and you can drop back to a more power-frugal relay for

driving the rest of the electronics on the airplane - a relay installed in

parallel.  I can't think of any downside.


	


   That would work too. I'm thinking that for small airplanes,

   the manual battery switch makes the most sense. They're light

   and inexpensive.



   I've got a prototype contactor power manager on the bench but

   didn't get to finish evaluating it before I had to pull

   the plugs and start moving equipment and inventory.



   It would allow the builder to achieve low power operation

   with an el-cheeso contactor. Further, if the contactor

   needs replacing, you don't have to replace the associated

   electronics too . . . and vice versa

        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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