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Is there a switch configuration that will do this?

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david(at)carter.net
Guest

Posted: Thu Jun 17, 2021 8:29 am Post subject: Is there a switch configuration that will do this?

I'd like to have a single switch control both my taxi lights & landing lights. Sounds simple enough, right? Here's the catch. I want to control the taxi lights directly from this switch by making a connection to +12v. The landing lights, however, will be controlled through the Garmin GAD 27 electrical controller "magic box" so that it can provide airspeed-based wig-wag. The GAD 27 light control switch input is active-low. 



How I'd like it to work:

1. Switch down - both lights off

2. Middle position - +12v supplied to the taxi lights. 

3. Top position - taxi lights no longer connected to +12v, GAD 27 light switch input connected to ground. 

I know I can do this with a relay, but I'd rather avoid adding an additional failure point. It's not the end of the world if I use separate switches for these functions, but I'd prefer they are combined on one switch. 

Thanks,

David

---

David Carter

david(at)carter.net (david(at)carter.net)

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david(at)carter.net
Guest

Posted: Thu Jun 17, 2021 1:59 pm Post subject: Is there a switch configuration that will do this?

 	  Quote: 	
		  > There MIGHT be a simple way to do this but it

  >>    depends on the 'pull down' current of the electrical

  >>    controller. Is there a spec for that device that speaks

  >>    to parameters of this input?

Here's what I was able to find in the installation manual: (top of page 26-8, or page 342 in Acrobat Reader)

https://static.garmin.com/pumac/190-01115-01_an.pdf

These active-low discrete inputs conform to the following specification:

Low: Vin < 3.5 VDC, or Rin < 375 Ω (input active)

High: Vin > 8 VDC, or Rin> 100k Ω (input inactive)

---

David Carter

david(at)carter.net (david(at)carter.net)

On Thu, Jun 17, 2021 at 5:37 PM Robert L. Nuckolls, III <nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)> wrote:

 	  Quote: 	
		    At 11:28 AM 6/17/2021, you wrote:

  	  Quote: 	
		  I'd like to have a single switch control both my taxi lights & landing lights. Sounds simple enough, right? Here's the catch. I want to control the taxi lights directly from this switch by making a connection toÂ +12v. The landing lights, however, will be controlled through the Garmin GAD 27 electricalÂ controller "magic box" so that it can provide airspeed-based wig-wag. The GAD 27 light control switch input is active-low.Â 

 How I'd like it to work:

 1. Switch down - both lights off

 2. Middle position -Â +12v supplied to the taxi lights.Â 

 3. Top position - taxi lights no longer connected toÂ +12v, GAD 27 light switch input connected to ground.Â 

 I knowÂ I can do this with a relay, but I'd ratherÂ avoid addingÂ an additionalÂ failure point. It's not the end of the world if I use separateÂ switches for these functions, but I'd prefer they are combined on one switch.Â 	

   There MIGHT be a simple way to do this but it

   depends on the 'pull down' current of the electrical

   controller. Is there a spec for that device that speaks

   to parameters of this input?

   Bob . . .

   Un impeachable logic: George Carlin asked, "If black boxes

   survive crashes, why don't they make the whole airplane

   out of that stuff?"

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user9253

Joined: 28 Mar 2008
Posts: 1922
Location: Riley TWP Michigan

Posted: Fri Jun 18, 2021 8:53 am Post subject: Re: Is there a switch configuration that will do this?

You need a DP3T ON-ON-ON switch.

Mouser and Digikey and others sell them.

https://www.mouser.com/Electromechanical/Switches/Toggle-Switches/_/N-5g2jZ1yzvvqx?P=1z0z2o3Z1z0z28f

https://www.digikey.com/en/products/filter/toggle-switches/201?s=N4IgjCBcpgzADFUBjKAzAhgGwM4FMAaEAeygG0RYAWeWAdgE4QBdIgBwBcoQBlDgJwCWAOwDmIAL5EATLACsSEKkiZchEuUoAOafABseluy6ReAkeKkgAtNMXKBAV3WlIFBcwlW7bkABEABVgAFRYJIA

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_________________
Joe Gores

david(at)carter.net
Guest

Posted: Mon Jun 21, 2021 10:49 am Post subject: Is there a switch configuration that will do this?

 	  Quote: 	
		     P.S. those 'loose' components present a small

   packaging problem.  I think I'd fabricate an

   assembly-under-heat-shrink of the three compoents

   with wires coming out each end.

   Use 1/2" dual wall heat shrink . . . that's

   how I packaged a few hundred crowbar ov management

   modules.

   Your finished assembly will be about 1-1/2 inches

   long and 3/8" in diameter. It would tie nicely

   into an adjacent wire bundle. I've got all the

   materials in stock. I could build one up for you.

	




Bob - thanks for the solution design & for the packaging tip. I was also wondering how much heat the resistor would need to dissipate in this application? I'm guessing not much? 

---

David Carter

david(at)carter.net (david(at)carter.net)

On Mon, Jun 21, 2021 at 12:26 PM Robert L. Nuckolls, III <nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)> wrote:



 	  Quote: 	
		     	  Quote: 	
		    This switch with addition of two

   diodes and the resistor cited above can be configured

   to accomplish the switching functions you requested.

   See attached: 	


    P.S. those 'loose' components present a small

    packaging problem.  I think I'd fabricate an

    assembly-under-heat-shrink of the three compoents

    with wires coming out each end.



    Use 1/2" dual wall heat shrink . . . that's

    how I packaged a few hundred crowbar ov management

    modules.



    Your finished assembly will be about 1-1/2 inches

    long and 3/8" in diameter. It would tie nicely

    into an adjacent wire bundle. I've got all the

    materials in stock. I could build one up for you.



 

   Bob . . .



   Un impeachable logic: George Carlin asked, "If black boxes

   survive crashes, why don't they make the whole airplane

   out of that stuff?"

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