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This switch OK?

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johngoodman

Joined: 18 Sep 2006
Posts: 530
Location: GA

Posted: Mon Mar 01, 2010 7:24 pm Post subject: This switch OK?

I'm looking at using this switch - will it work in a 14v system?



John

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#40572 Phase One complete in 2011

user9253

Joined: 28 Mar 2008
Posts: 1944
Location: Riley TWP Michigan

Posted: Tue Mar 02, 2010 6:55 pm Post subject: Re: This switch OK?

 	  Quote: 	
		  I'm looking at using this switch - will it work in a 14v system? 	




John,

Yes, it will work.  Voltage is not an issue for this switch in your airplane.  Current is the issue.  The picture does not specify 250V AC or DC.  I will assume that it is AC.  I think it should be safe to use this switch to handle up to 5 amps at 14VDC.  A switch will not immediately self-destruct if operated slightly above its rating.  But its life will be shortened.  How much current do you want to control with this switch and what type of load is it?

Joe

_________________
Joe Gores

johngoodman

Joined: 18 Sep 2006
Posts: 530
Location: GA

Posted: Wed Mar 03, 2010 5:05 am Post subject: Re: This switch OK?

 	  Quote: 	
		  The picture does not specify 250V AC or DC.  I will assume that it is AC.  I think it should be safe to use this switch to handle up to 5 amps at 14VDC.  A switch will not immediately self-destruct if operated slightly above its rating.  But its life will be shortened.  How much current do you want to control with this switch and what type of load is it?

Joe 	




I want to use it for Coil Power for a GearedDrives LS1 V8 engine in an RV-10. I'm not sure what the Coil actually draws but the wire is protected by a 15 amp fuse. The wire from the engine looks like a 14 or 16awg. I'll have to look into the actual draw, but this switch will probably not work since I need reliability. Thanks for the reply,

John

_________________
#40572 Phase One complete in 2011

ulflyer(at)verizon.net
Guest

Posted: Wed Mar 03, 2010 3:28 pm Post subject: This switch OK?

John,

Reading your reply to other folks replies I am concerned of your 

using this switch for your intended application.



First off, the switch information you provided in the attachment does 

not designate if it is rated for AC or DC current.  Note, an AC rated 

switch if used in an DC current application, the DC current capacity 

will normally be only a fraction of it's AC current rating.  Second, 

I would point out that the reply by Joe saying that you could 

probably run 5 amps of current exceeds the switches current rating, 

if it turns out to be an AC application switch, you would be further 

outside the switches safe operating limits.  Neither would be 

acceptable solution.



I strongly recommend you determine your current needs for the circuit 

your controlling.  Then determine if the switch your considering is 

AC or DC rated.  If the switch is AC rated,  find another switch 

appropriate for your application.  Do it right the first time, you 

might not get the second chance to do it over again.

jerryb



 	  Quote: 	
		  Attachments:



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nuckolls.bob(at)aeroelect
Guest

Posted: Wed Mar 03, 2010 4:55 pm Post subject: This switch OK?

 	  Quote: 	
		  I want to use it for Coil Power for a GearedDrives LS1 V8 engine in 

an RV-10. I'm not sure what the Coil actually draws but the wire is 

protected by a 15 amp fuse. The wire from the engine looks like a 14 

or 16awg. I'll have to look into the actual draw, but this switch 

will probably not work since I need reliability. Thanks for the reply,


	


    What coil? Ignition? The picture I saw appears to

    be a momentary push button. If it has 3 terminals,

    then I suspect it's a single-pole, double-throw

    device. Further, push-buttons of this style are

    slow-make, slow-break (no fast acting over-center

    mechanism). VERY poor technology for switching

    reactive DC loads.



    Bob . . .

user9253

Joined: 28 Mar 2008
Posts: 1944
Location: Riley TWP Michigan

Posted: Wed Mar 03, 2010 6:21 pm Post subject: Re: This switch OK?

Looking at the picture of this switch (made in UK), the first thing that came to mind is that it was going to be used for a starter switch.  It turns out that John intends to use it for a more critical application where a high quality switch should be used.  So I take back what I said about the switch being ok to use.

   As a general rule, a 125VAC rated switch can handle the same current at 14VDC, even if the manufacturer does not publish the DC rating.  Every AC switch has a DC ampacity.  That ampacity might not have been determined by testing and thus is unknown.

  Jerry B. said,  	  Quote: 	
		  "the DC current capacity will normally be only a fraction of it's AC current rating." 	
  That is true if the voltage remains the same: 250V in this case.  But, generally speaking, a 125VAC rated switch can carry as much DC current at 14V as it can carry AC current at 125V.  An example of this can be seen by reading the data sheet for another switch.  http://www.nkkswitches.com/pdf/stoggleslowcap.pdf

Notice that 125VAC rating is identical to the 30VDC rating.  At 14VDC, this switch can handle even more.  Also notice that this switch can handle 2 1/2 times the current at 30VDC than it can at 250VAC.  Most good quality snap action AC switches are suitable for use in homebuilt aircraft as long as the 14VDC current does not exceed the 125VAC rating of the switch.

Comments are welcome.

Joe

_________________
Joe Gores

fvalarm(at)rapidnet.net
Guest

Posted: Wed Mar 03, 2010 9:47 pm Post subject: This switch OK?

Remember...



Switches manufactured in the UK will not work in any north American aircraft

(certified or amateur built) as the current flow requirement is OPPOSITE to

what we consider normal.  This is why many switch configurations in the UK

call for switch orientation to be up to be OFF and down to be ON. 



Just trying to help.  We're all in this together.  Keep yur sticks on the

ice.



Bevan  

--

tomcostanza

Joined: 19 Oct 2008
Posts: 49

Posted: Thu Mar 04, 2010 3:27 am Post subject: Re: This switch OK?

 	  Quote: 	
		  Remember... 



Switches manufactured in the UK will not work in any north American aircraft 

(certified or amateur built) as the current flow requirement is OPPOSITE to 

what we consider normal. This is why many switch configurations in the UK 

call for switch orientation to be up to be OFF and down to be ON. 	




Is this because of that Coriolis thingy?  I thought things only went backwards in the southern hemisphere.



Do not archive

_________________
Clear Skies,
Tom Costanza
-- in year 17 of a 3 year project

bakerocb

Joined: 15 Jan 2006
Posts: 727
Location: FAIRFAX VA

Posted: Thu Mar 04, 2010 5:24 am Post subject: This switch OK?

3/4/2010



Hello Bevan, You wrote:



1) "......as the current flow requirement is OPPOSITE to what we consider 

normal."



{Response} Yes, it is those perverse European electrons that cause this 

problem. You can imagine what a nuisance it is for all those airplanes 

flying across the Atlantic ocean to have to reposition all of their switches 

when they go from one electron area to the other.



2) "  This is why many switch configurations in the UK call for switch 

orientation to be up to be OFF and down to be ON."



{Response} Some recalcitrant European homebuilders have even been known to 

install their switches up side down to avoid this problem. Please don't 

alert the European homebuilder police to this pernicious activity.



3) "Keep yur sticks on the ice."



{Response} Strange advice. All of my girl friends and even some of my wives 

have insisted that I keep my stick in my pants.



'OC' Says: "The best investment we can make is the effort to gather and 

understand knowledge."



DO NOT ARCHIVE



===============================================



Time: 09:47:14 PM PST US

From: "B Tomm" <fvalarm(at)rapidnet.net>

Subject: RE: Re: This switch OK?

Remember...



Switches manufactured in the UK will not work in any north American aircraft

(certified or amateur built) as the current flow requirement is OPPOSITE to

what we consider normal.  This is why many switch configurations in the UK

call for switch orientation to be up to be OFF and down to be ON. 



Just trying to help.  We're all in this together.  Keep yur sticks on the

ice.



Bevan

johngoodman

Joined: 18 Sep 2006
Posts: 530
Location: GA

Posted: Thu Mar 04, 2010 6:45 am Post subject: Re: This switch OK?

I'd like to thank everybody for the interest - I've learned a lot about switches (g).

I've moved on from that switch to possibly this one, but I still need to find out the actual amps on the Coil first:



Included:  

1 x Clear Illuminated Button

1 x Protector Cover

1 x Label Sheet (Water Spray, Wipers, Lights, Nitrous, Fan, etc.)

Specifications: 

Switch Acutation Style: Push Button

Circuit Activation: Constant

Lighted: Yes (White)

Amp Rating: 10A

Volt Rating: 30VDC

Terminal Type: Blade

Material: Plastic

Quantity: Sold Individually

Mounting Size: 16mm or 5/8"



John

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nuckolls.bob(at)aeroelect
Guest

Posted: Thu Mar 04, 2010 7:23 am Post subject: This switch OK?

At 08:46 AM 3/4/2010, you wrote:

 	  Quote: 	
		  

<johngoodman(at)earthlink.net>



I'd like to thank everybody for the interest - I've learned a lot 

about switches (g).

I've moved on from that switch to possibly this one, but I still 

need to find out the actual amps on the Coil first:


	


   It would sure help if we understood exactly what

   this switch is supposed to do. Do you need

   push-on, push-off (alternate action) or simply

   push-on (momentary but spring loaded to off).



   Exactly how does the switch under study integrate

   into your airplane . . . and is there a reason

   it shouldn't be but one of several switches that

   accomplish different tasks? Like one of a row

   of switches that control DC power, landing lights,

   nav lights, etc.



   In other words, why this decidedly odd

   device in a machine that will undoubtedly have

   several other switches?



   Bob . . .

johngoodman

Joined: 18 Sep 2006
Posts: 530
Location: GA

Posted: Thu Mar 04, 2010 8:42 am Post subject: Re: This switch OK?

 	  Quote: 	
		  It would sure help if we understood exactly what 

this switch is supposed to do. Do you need 

push-on, push-off (alternate action) or simply 

push-on (momentary but spring loaded to off). 



Exactly how does the switch under study integrate 

into your airplane . . . and is there a reason 

it shouldn't be but one of several switches that 

accomplish different tasks? Like one of a row 

of switches that control DC power, landing lights, 

nav lights, etc. 



In other words, why this decidedly odd 

device in a machine that will undoubtedly have 

several other switches? 



Bob . . . 	


I guess some explanation is in order, sorry about that. I'm looking for a unique switch for Coil Power for my GearedDrives LS1 engine. The panel has a VP200 and no other switches except two battery switches that look just like the VP200 switches (autopilot does have a couple of micros).

The reason for a Coil switch is that I need a quick way to kill the engine. There is no key, and the VP takes care of starting. Otherwise I would have to remove power from the battery busses to stop the engine at the end of the flight. This would kill everything at once, unless I did some power isolation first.

So, I'm looking for a Latching Pushbutton, preferably lit when on. It needs to be obvious to the passengers that it powers the engine. In reality, I think it only draws about 3 amps, 5 at most. Think of it as the "run" position of your keyed ignition.

Hope this helps.

John

_________________
#40572 Phase One complete in 2011

nuckolls.bob(at)aeroelect
Guest

Posted: Thu Mar 04, 2010 9:10 am Post subject: This switch OK?

 	  Quote: 	
		  

I guess some explanation is in order, sorry about that. I'm looking 

for a unique switch for Coil Power for my GearedDrives LS1 engine. 

The panel has a VP200 and no other switches except two battery 

switches that look just like the VP200 switches (autopilot does have 

a couple of micros).

The reason for a Coil switch is that I need a quick way to kill the 

engine. There is no key, and the VP takes care of starting. 

Otherwise I would have to remove power from the battery busses to 

stop the engine at the end of the flight. This would kill everything 

at once, unless I did some power isolation first.

So, I'm looking for a Latching Pushbutton, preferably lit when on. 

It needs to be obvious to the passengers that it powers the engine. 

In reality, I think it only draws about 3 amps, 5 at most. Think of 

it as the "run" position of your keyed

ignition.


	


    What do your other switches look like? Are

    they all the same kind of switch? Are there

    other switches that go to control of engine

    accessories? Fuel pumps? Why not an identical

    switch that says "IGNITION ON" when up and

    "OFF" when down?



    The device you're considering has a much more

    complex internal mechanism than the plain-vanilla

    toggle switch. You speak to "removing power from the

    battery busses to stop the engine". What devices

    feed from battery busses and how are they controlled

    to disconnect while the airplane is parked? Is any

    single feed from the battery bus required for

    the engine to function . . . does that feed power

    a device has a backup? You speak to "busses" . . .

    so I presume you have dual batteries with 1/2 of

    engine-critical loads powered from each battery . . .

    how is the change-over from "primary" to "secondary"

    hardware accomplished?



      Bob . . .

user9253

Joined: 28 Mar 2008
Posts: 1944
Location: Riley TWP Michigan

Posted: Thu Mar 04, 2010 10:16 am Post subject: Re: This switch OK?

John,

If this switch is going to kill the engine, what will happen if the switch fails while flying?  Assuming that you have two ignition systems, there should be one switch for each.  Is that what you have planned?  

Joe

_________________
Joe Gores

klehman(at)albedo.net
Guest

Posted: Thu Mar 04, 2010 11:49 am Post subject: This switch OK?

John

If like many of us here you looking for more than just a yes or no 

answer, you might consider that most of us running EFI

systems do not cut ignition power to kill the engine. (I'm assuming you 

have EFI) That leaves fuel in the cylinders and (same as a Lycoming) can 

be a safety hazard if someone moves the prop on a hot engine. Most EFI 

computers will kill the fuel before the ignition.



The next preferred shutdown method would likely be to kill power to the

electric fuel pump(s). That is what I do when I taxi in on my backup EFI 

system. Anything other than a normal system shutdown can  set engine 

codes on some computers though.



I do control power to my secondary ignition coils through a toggle 

switch but I never shutdown the engine that way.



Ken



johngoodman wrote:

 	  Quote: 	
		   

 <johngoodman(at)earthlink.net>

 

  

 

 I guess some explanation is in order, sorry about that. I'm looking

 for a unique switch for Coil Power for my GearedDrives LS1 engine.

 The panel has a VP200 and no other switches except two battery

 switches that look just like the VP200 switches (autopilot does have

 a couple of micros). The reason for a Coil switch is that I need a

 quick way to kill the engine. There is no key, and the VP takes care

 of starting. Otherwise I would have to remove power from the battery

 busses to stop the engine at the end of the flight. This would kill

 everything at once, unless I did some power isolation first. So, I'm

 looking for a Latching Pushbutton, preferably lit when on. It needs

 to be obvious to the passengers that it powers the engine. In

 reality, I think it only draws about 3 amps, 5 at most. Think of it

 as the "run" position of your keyed ignition. Hope this helps. John

 

 -------- #40572 QB. Engine on, wing attach coming soon. Panel

 delivery soon. N711JG reserved

ulflyer(at)verizon.net
Guest

Posted: Thu Mar 04, 2010 6:47 pm Post subject: This switch OK?

Whoa there Joe,

Wow!  Can't believe your saying using use AC rated switches for DC 

applications at near the full AC current rating is OK.  No way.



AC switches take advantage of the AC zero crossing for reducing 

contact arcing and welding.  (The reason DC switches amp for amp 

typically cost more than AC switches, there made different to reduce 

and eliminate contact arcing and welding.)  And suddenly you say 

using the switch the gentlemen asked about is OK and  justify your 

recommendation upon the spec's of a totally different switch.  Use 

the right type of switch for your application.  Maybe you can 

convince the folks that select the switches used for DC powered 

landing gear applications to use AC designated switches.  Just don't 

think you'll quite sell them on your method.

jerb





At 06:21 PM 3/3/2010, you wrote:

 	  Quote: 	
		  



Looking at the picture of this switch (made in UK), the first thing 

that came to mind is that it was going to be used for a starter 

switch.  It turns out that John intends to use it for a more 

critical application where a high quality switch should be used.  So 

I take back what I said about the switch being ok to use.

    As a general rule, a 125VAC rated switch can handle the same 

 current at 14VDC, even if the manufacturer does not publish the DC 

 rating.  Every AC switch has a DC ampacity.  That ampacity might 

 not have been determined by testing and thus is unknown.

   Jerry B. said,

 > "the DC current capacity will normally be only a fraction of it's 

 AC current rating."

   That is true if the voltage remains the same: 250V in this 

 case.  But, generally speaking, a 125VAC rated switch can carry as 

 much DC current at 14V as it can carry AC current at 125V.  An 

 example of this can be seen by reading the data sheet for another 

 switch.  http://www.nkkswitches.com/pdf/stoggleslowcap.pdf

Notice that 125VAC rating is identical to the 30VDC rating.  At 

14VDC, this switch can handle even more.  Also notice that this 

switch can handle 2 1/2 times the current at 30VDC than it can at 

250VAC.  Most good quality snap action AC switches are suitable for 

use in homebuilt aircraft as long as the 14VDC current does not 

exceed the 125VAC rating of the switch.

Comments are welcome.

Joe



--------

Joe Gores

johngoodman

Joined: 18 Sep 2006
Posts: 530
Location: GA

Posted: Thu Mar 04, 2010 6:53 pm Post subject: Re: This switch OK?

Sorry that I've got everybody wondering; I'll try to explain.



The GearedDrives LS1 Corvette engine is just like a car. In a traditional car, the key has several positions, the last rotation is "start", and it is spring loaded to come out of start to "run." The "run" position is Coil power. It is not actual Coil power which is a lot of juice, just a relay out "under the hood." When you turn off a car, you don't starve it of fuel like airplanes normally do, you kill the coil power.



As far as my switches, The VP200 does everything with soft switches and it's switch panel. The Master Battery and Aux Battery switches are positioned next to the switch panel and are the same brand of switches. The two fuel pumps and the Engine Crosstie will be on three guarded switches on the console, under the panel, that will be normally on. See Z-19 but add a crosstie between the two batteries, put the engine battery bus on the "on" side, but leave the Keep Alive power for the ECU on the engine battery hot side.



There shouldn't be fuel in the cylinders because the ECU won't inject any and the fuel rail regulator is closed. The prop is not connected to the engine because the clutch has released around 700 rpm. You can spin the prop all you want. Fuel is still pumping but isn't getting past the Filter/Regulator which returns all the fuel to the tanks. Fuel can be stopped by turning off the batteries or opening the guarded pump switches.



I'm sure a lot of you think this is wrong, but I'm really not asking. I'm only trying to find a good Kill Switch that is so obvious that even a Cave Man Can Do It.

I'm still amazed that a guy steered a stuck pedal Toyota for 6 miles without ever thinking about the shift stick or the key....



John

_________________
#40572 Phase One complete in 2011

ulflyer(at)verizon.net
Guest

Posted: Thu Mar 04, 2010 6:54 pm Post subject: This switch OK?

At 03:27 AM 3/4/2010, you wrote:

 	  Quote: 	
		  

<Tom(at)CostanzaAndAssociates.com>

 > Remember...

 >

 > Switches manufactured in the UK will not work in any north 

 American aircraft

 > (certified or amateur built) as the current flow requirement is 

 OPPOSITE to

 > what we consider normal. This is why many switch configurations in the UK

 > call for switch orientation to be up to be OFF and down to be ON.



Is this because of that Coriolis thingy?  I thought things only went 

backwards in the southern hemisphere.

They do go backwards which is why some toilets (aka water closets) 
	


designed to work in one hemisphere will not work or not nearly as 

well if put into service in the opposite hemisphere for which they 

were designed to operate which leads me to conclude this thread is 

headed for the crapper. 

jerb

 	  Quote: 	
		  Do not archive



--------

Clear Skies,

Tom Costanza





Read this topic online here:



http://forums.matronics.com/viewtopic.php?p=289167#289167

user9253

Joined: 28 Mar 2008
Posts: 1944
Location: Riley TWP Michigan

Posted: Thu Mar 04, 2010 8:36 pm Post subject: Re: This switch OK?

 	  Quote: 	
		  Wow! Can't believe your saying using use AC rated switches for DC applications at near the full AC current rating is OK. No way. 	


JERB,

I am not the only one who thinks that it is OK to use AC rated switches in airplanes.  Read the last paragraph on Page 2 and page 3 of this document written by a well respected electrical guru, 

http://www.aeroelectric.com/articles/Switch_Ratings.pdf

Here is a quote from that article:" 	  Quote: 	
		  In a nutshell, 125 VAC ratings equate favorably and conservatively to 14 VDC ratings - as long as the switch has a healthy "snap" action . . .The switches we stock sell for $5.00 in a single-pole device and carry no markings for DC ratings.  They are rated at 7 amps or better at 115 AC and will work just fine in virtually every slot on an airplane panel."

_________________
Joe Gores

nuckolls.bob(at)aeroelect
Guest

Posted: Thu Mar 04, 2010 9:41 pm Post subject: This switch OK?

At 10:36 PM 3/4/2010, you wrote:

 	  Quote: 	
		  

 > Wow! Can't believe your saying using use AC rated switches for DC 

 applications at near the full AC current rating is OK. No way.


	


    All switches have ac and dc capabilities at some level.

    Just because the ratings on the printed on the side of

    the switch are given at 120 or 240 VAC simply speaks

    to the largest market into which they are sold. It

    doesn't mean that they don't have useful and quite

    rational application in DC systems. The comparative

    ratings charts for switches in any well written

    switch catalog will confirm this assertion.



    The voltage rating of a switch is driven mostly by

    it's ability to break a circuit . . . spread the

    contacts fast enough so that the fire goes out

    before damage is done. The intensity of that fire

    is proportional to the current in the circuit at

    the time the contacts open.



    So a switch with contacts that don't overheat at

    7A will CARRY that much current at any voltage but

    the current may have to be de-rated at the higher

    DC voltages . . . because it's harder to put the

    BREAK the circuit without generating a lot of heat.



    Bob . . .

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