Matronics Email Lists :: View topic - S704-1 Relay Question

Matronics Email Lists
Web Forum Interface to the Matronics Email Lists

Get Email Distribution Too! FAQ Search Memberlist Usergroups Register

Profile Log in to check your private messages Log in

S704-1 Relay Question

Matronics Email Lists Forum Index -> AeroElectric-List

View previous topic :: View next topic

Author Message

hammer408(at)comcast.net
Guest

Posted: Sun May 18, 2008 10:35 am Post subject: S704-1 Relay Question

Bob:



I'm going to install a "Heavy E-bus and use your architecture: Bat-bus

(14AWG) to 704-1 relay with S700-1-3(22AWG) switch coming off relay and 14

awg from relay to e-bus.  I'm a little confused on how the Relay is wired.

I've printed the wiring picture of the Relay off the aeroelectric website

and it didn't help.



The diode, via fastabs is wired or jumps the - to + terminal and there are

also 2 wires crimped to the same fasttabs. I'm assuming the black goes to

ground, but where does the one wired to the + terminal go to ??



Also where does the "COM" wire and N.O. wire go?



OR...keeping the question simple ---how do you wire the Relay utilizing

Heavy E-Bus architecture?



Thanks

nuckolls.bob(at)cox.net
Guest

Posted: Sun May 18, 2008 7:36 pm Post subject: S704-1 Relay Question

At 02:34 PM 5/18/2008 -0700, you wrote:



 	  Quote: 	
		  

<hammer408(at)comcast.net>



Bob:



I'm going to install a "Heavy E-bus and use your architecture: Bat-bus

(14AWG) to 704-1 relay with S700-1-3(22AWG) switch coming off relay and 14

awg from relay to e-bus.  I'm a little confused on how the Relay is wired.

I've printed the wiring picture of the Relay off the aeroelectric website

and it didn't help.



The diode, via fastabs is wired or jumps the - to + terminal and there are

also 2 wires crimped to the same fasttabs. I'm assuming the black goes to

ground, but where does the one wired to the + terminal go to ??



Also where does the "COM" wire and N.O. wire go?



OR...keeping the question simple ---how do you wire the Relay utilizing

Heavy E-Bus architecture?



Thanks


	


   As shown in



  http://www.aeroelectric.com/PPS/Adobe_Architecture_Pdfs/Z32K.pdf



   The picture at:



http://aeroelectric.com/Pictures/Relays/s704inst.jpg



   shows how to get the diode leads into the same terminals

   with the wires that go to ends of the relay coil . . . but

   according to Z32K you'll need to drop two wires into the

   COM terminal too.



   Bob . . .



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

        ( . . .  a long habit of not thinking   )

        ( a thing wrong, gives it a superficial )

        ( appearance of being right . . .       )

        (                                       )

        (                  -Thomas Paine 1776-  )

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

andrewbutler(at)ireland.c
Guest

Posted: Mon May 19, 2008 5:14 am Post subject: S704-1 Relay Question

Hello,



At what level of load does an E-Bus become "heavy duty"?



Also, what is the purpose of the diode? I know what a diode does, but what is its practical use in this instance?



Cheers,



Andrew.

 

 [quote]---

rshannon

Joined: 05 Sep 2007
Posts: 62

Posted: Mon May 19, 2008 6:11 am Post subject: S704-1 Relay Question

On Mon, May 19, 2008 at 6:11 AM, Andrew Butler <andrewbutler(at)ireland.com (andrewbutler(at)ireland.com)> wrote:

 	  Quote: 	
		     Hello,



At what level of load does an E-Bus become "heavy duty"?



Also, what is the purpose of the diode? I know what a diode does, but what is its practical use in this instance?



Cheers,

 

Andrew.

 

	


The level at which an E-bus becomes "heavy duty" is not a precise point, but certainly occurs when the E-bus is expected to carry loads that would strain or exceed limits for a standalone toggle switch. Although the S700 series switches are rated to 15A, you should probably be seriously considering a separate relay whenever load approaches 10A, IMHO.

 

 The diode keeps the E-bus from back feeding the Main bus when the E-bus alternate feed (direct from battery or battery bus) is ON. If the E-bus were allowed to back feed the Main bus, it would defeat the purpose of the E-bus, which is rapid, positive reduction of load upon alternator failure. Use of a diode instead of another switch eliminates the need to flip another switch (i.e., reduces chance for error, also, see "heavy duty" discussion above).

 

 Ron



  [quote][b]

andrewbutler(at)ireland.c
Guest

Posted: Mon May 19, 2008 7:19 am Post subject: S704-1 Relay Question

Thanks Ron, though the diode I was referring is the 1N4001 across the coil of the S704 relay. There is something I don't know, cause I don't see it adding any functionality.......



Andrew.

 

 [quote]---

etienne.phillips(at)gmail
Guest

Posted: Mon May 19, 2008 7:44 am Post subject: S704-1 Relay Question

It's called a fly-back diode.



The coil of a relay is a fairly sizeable inductor, which means that a step-change in current is not really possible. What happens when the current to the coil is removed, the "inertia" of the inductor will force a current to continue flowing for a short while, generating large voltages and arcing across switch contacts. The fly-back diode gives this current a path to flow without interfering with the rest of the electrical system, and only comes into play when the coil is de-energized.

 

For more info, go to http://en.wikipedia.org/wiki/Flyback_diode







Etienne



2008/5/19 Andrew Butler <andrewbutler(at)ireland.com (andrewbutler(at)ireland.com)>:

 [quote]  Thanks Ron, though the diode I was referring is the 1N4001 across the coil of the S704 relay. There is something I don't know, cause I don't see it adding any functionality.......



Andrew.

 

 [quote]---

rshannon

Joined: 05 Sep 2007
Posts: 62

Posted: Mon May 19, 2008 7:46 am Post subject: S704-1 Relay Question

On Mon, May 19, 2008 at 8:16 AM, Andrew Butler <andrewbutler(at)ireland.com (andrewbutler(at)ireland.com)> wrote:

 	  Quote: 	
		     Thanks Ron, though the diode I was referring is the 1N4001 across the coil of the S704 relay. There is something I don't know, cause I don't see it adding any functionality.......



Andrew.

	
  

Ooops! So much for unwarranted assumptions.



As for the diode across the coil, see http://www.aeroelectric.com/articles/spikecatcher.pdf

 

Ron



  [quote][b]

andrewbutler(at)ireland.c
Guest

Posted: Mon May 19, 2008 8:17 am Post subject: S704-1 Relay Question

Perfect! Thanks.

 

 [quote]---

nuckolls.bob(at)cox.net
Guest

Posted: Mon May 19, 2008 12:11 pm Post subject: S704-1 Relay Question

At 01:11 PM 5/19/2008 +0000, you wrote:



 	  Quote: 	
		  Hello,



At what level of load does an E-Bus become "heavy duty"?


	


    The e-bus was born of a time when many if not most

    builders could plan on and implement an endurance

    load of 5A or less. The rule-of-thumb for maximum

    protection level of an always hot wire in TC aircraft

    is 5A . . . so the idea of taking a 5A fused feeder

    off the battery bus to supply an e-bus through a panel

    mounted switch was well within the parameters of

    accepted practice in TC aircraft.



    As folks piled more stuff on the e-bus, 5A feeders

    wouldn't cut it any more so it became a tribute

    to accepted practice to add a mini battery contactor

    at the battery bus to provide a local control point for

    the e-bus alternate feed path.



    From a reliability perspective I really like the

    idea of staying with a toggle switch. Further,

    given that a 7A fuse is on the order of 5-10 times

    faster than a 5A breaker, it seems a reasonable

    tribute to accepted practice to say that anything

    over a 7A FUSED alternate feed path is "heavy duty"

    and justifies the complexity of an additional

    relay. 7A or less can be handled with a toggle

    switch.



    Bob . . .

andrewbutler(at)ireland.c
Guest

Posted: Tue May 20, 2008 1:11 am Post subject: S704-1 Relay Question

Okay, I've read the Wikipedia and aeroelectric articles. So far so good.



So, in the absence of the diode, where is the "arc" likely to occur? If I have understood correctly I'm saying at the E-BUS feed switch rather than at the switch in the relay. Am I correct?



If not, why does the arc occur at the relay switch and not the feed switch. It has to do with the current flow path.........



Thanks for your help.



Andrew.

 

 [quote]---

etienne.phillips(at)gmail
Guest

Posted: Tue May 20, 2008 5:35 am Post subject: S704-1 Relay Question

That is correct, in the E-bus Alternate Feed Switch in this case, or in a more general case when dealing with inductor-like components, it'll arc across whatever component tries to remove power to the relay. In the case of a solid-state IC, this will normally be the silicon wafer, which would let out the smoke and kill the chip.

 

I know someone who lost a starter switch in his Cozy after about 15 engine starts because the fly-back diode was missing from the starter contactor, that's how marked the effect is... A new switch and one 50c fly-back diode later and no more problems.

 

Hope that helps 

Etienne



2008/5/20 Andrew Butler <andrewbutler(at)ireland.com (andrewbutler(at)ireland.com)>:

[quote]   Okay, I've read the Wikipedia and aeroelectric articles. So far so good.



So, in the absence of the diode, where is the "arc" likely to occur? If I have understood correctly I'm saying at the E-BUS feed switch rather than at the switch in the relay. Am I correct?

 

If not, why does the arc occur at the relay switch and not the feed switch. It has to do with the current flow path.........



Thanks for your help.



Andrew.

 

 [quote]---

nuckolls.bob(at)cox.net
Guest

Posted: Tue May 20, 2008 6:10 am Post subject: S704-1 Relay Question

At 09:01 AM 5/20/2008 +0000, you wrote:



 	  Quote: 	
		  Okay, I've read the Wikipedia and aeroelectric articles. So far so good.



So, in the absence of the diode, where is the "arc" likely to occur? If I 

have understood correctly I'm saying at the E-BUS feed switch rather than 

at the switch in the relay. Am I correct?



If not, why does the arc occur at the relay switch and not the feed 

switch. It has to do with the current flow path.........



Thanks for your help.



Andrew.


	


    Not sure what you're calling the "feed switch". With

    respect to contactors and relays, there is potential for

    effects of field collapse in an inductor to erode

    the contacts of the device that controls that contactor

    or relay. Hence, the long standing practice of adding

    spike suppression across the coils of such devices as

    illustrated in the Z-figures.



    Now, ANY time you break a circuit with the opening

    of hard contacts as in a switch, relay or contactor

    (that is carrying any amount of current at any voltage)

    there WILL be an arc formed in spreading gap between

    opening contacts. There was a school of thought circulated

    in the OBAM aircraft community a few years ago that

    for voltages and/or currents below some low level

    (I don't recall the numbers now) that no arcing would

    occur.



    So as an experiment, I took a miniature switch and

    sanded out the side of it like this:



http://aeroelectric.com/Pictures/Switches/sm_switch_cutaway.jpg



    I fixtured it under the microscope and caused the

    NO contacts to carry 1 or 1/2 amp of current at 1.5

    volts (alkaline d-cell). In a dark room I could clearly

    observe a tiny but bright blue arc in the spreading

    gap between the contacts when the circuit was broken.



    THIS ARCING IS NOT the phenomenon of concern with

    respect to noise or debilitating effects on controlling

    or controlled devices. Hence we rarely see arc suppression

    techniques applied to these effects. One exception

    is the quest for achieving the Beech Aircraft ov relay

    trip-life using relays some 30+ years ago as described

    in the chapter on OV Protection in the 'Connection.



    There is also a school of thought that suggests plain

    vanilla diodes across relay and contactor coils will

    cause a slowing of contact spreading velocity and is

    therefore an inducement to prolonged arcing at the

    opening contacts.



    Experiments on my bench showed that while adding a

    diode did indeed cause a DELAY IN OPENING of the

    contacts . . .



http://www.aeroelectric.com/Pictures/Curves/704-1DelayNoDiode.gif



http://www.aeroelectric.com/Pictures/Curves/704-1DelayWithDiode.gif



     . . . use of the plain vanilla diode produced no

    significant slowing of contact spreading velocity

    once they started to move.



http://www.aeroelectric.com/Pictures/Curves/704-1OpeningTimeNoDiode.gif



http://www.aeroelectric.com/Pictures/Curves/704-1OpeningTimeWithDiode.gif



    In any case, the arcing produced either at controlling

    switches -OR- contacts of the controlled devices IS

    NOT a widespread threat for damage to other components

    in the system. The strongest effect you'll experience

    from the behavior of an unsuppressed relay or contactor

    coil is a transient interference event. A few years ago

    I helped a builder track down why opening his avionics

    bus relay on an off-the-shelf integrated power distribution

    system caused his ov protection to trip.  A diode

    across the relay coil fixed the problem.



    Bob . . .

andrewbutler(at)ireland.c
Guest

Posted: Tue May 20, 2008 6:48 am Post subject: S704-1 Relay Question

All I ever wanted to know about that particular component on the Z-figures and then some.



I very much appreciate this valuable resource (all things Aeroelectric) and your attention to detail Bob. I wired up my first harness last weekend and attached it to my TruTrak servo. I did so with a relative amount of confidence in what I was doing, how I was doing it, why I was doing it and how I would continue doing it for the rest of the electrical system. Fantastic!



Without this resource, I can honestly say that I would have been groping in the dark ending up with a low quality piecemeal whole rather than a high quality coherent one.



Very many thanks for this and for the answers to my future questions. Andrew.

 [quote]---

longg(at)pjm.com
Guest

Posted: Tue May 20, 2008 9:26 am Post subject: S704-1 Relay Question

Great  thread...

  

 In our  world it seems like we take relays for granted. They are amazing gadgets  and I wanted to find more information on them. Below is a great link with detail  on the very popular Bosch relay. It should be very clear as to their great  benefit. There is no reason to stress a switch with a few of these in-line.  

  

 http://www.bcae1.com/relays.htm#demo

 [quote]   

   --

nuckolls.bob(at)cox.net
Guest

Posted: Tue May 20, 2008 4:40 pm Post subject: S704-1 Relay Question

At 02:45 PM 5/20/2008 +0000, you wrote:



 	  Quote: 	
		  All I ever wanted to know about that particular component on the Z-figures 

and then some.



I very much appreciate this valuable resource (all things Aeroelectric) 

and your attention to detail Bob. I wired up my first harness last weekend 

and attached it to my TruTrak servo. I did so with a relative amount of 

confidence in what I was doing, how I was doing it, why I was doing it and 

how I would continue doing it for the rest of the electrical system. Fantastic!



Without this resource, I can honestly say that I would have been groping 

in the dark ending up with a low quality piecemeal whole rather than a 

high quality coherent one.



Very many thanks for this and for the answers to my future questions. Andrew.


	


   You're most welcome my friend. I'm pleased that you've

   found the work so useful.



   Bob . . .

Display posts from previous:

	Matronics Email Lists Forum Index -> AeroElectric-List	All times are GMT - 8 Hours
Page 1 of 1

Jump to:

You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
You cannot attach files in this forum
You can download files in this forum