Matronics Email Lists :: View topic - Question on switch wiring

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

Question on switch wiring

Matronics Email Lists Forum Index -> AeroElectric-List

View previous topic :: View next topic

Author Message

longg(at)pjm.com
Guest

Posted: Mon Feb 08, 2010 10:42 am Post subject: Question on switch wiring

I bought a SPST 12 volt lighted switch from digi-key which I would like to use as a fuel pump indicator switch.  

   

SWITCH TOGGLE ILLUM SPST 20A GRN  

SCHED B: 853650  

ECCN: EAR99  

LEAD: LEAD ALL  

ROHS:  

ROHS NONC  

CH652-ND  

   

Assumptions: My fuel pump runs via a relay switch (20 amp B & C S704-1 job).  

   

   

   

Question: The switch is provided with a third 1/4” tab on the top (on position) of the switch. Normal use is to add a jumper from the on position to the top tab to illuminate light when turned on.  

   

The switch works great when used with standard power/ground connection, e.g. landing light. When I use it in conjunction with the relay switch, the light comes on when the switch is in the off position.   

   

Ideas appreciated.  

   

Glenn  

      [quote][b]

- The Matronics AeroElectric-List Email Forum -

Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

http://www.matronics.com/Navigator?AeroElectric-List

nuckolls.bob(at)aeroelect
Guest

Posted: Mon Feb 08, 2010 12:09 pm Post subject: Question on switch wiring

At 12:33 PM 2/8/2010, you wrote:

  	  Quote: 	
		  I bought a SPST 12 volt lighted switch from digi-key which I would like to use as a fuel pump indicator switch.

  

 SWITCH TOGGLE ILLUM SPST 20A GRN

 SCHED B: 853650

 ECCN: EAR99

 LEAD: LEAD ALL

 ROHS:

 ROHS NONC

 CH652-ND

  

 Assumptions: My fuel pump runs via a relay switch (20 amp B & C S704-1 job).

  

  

  

 Question: The switch is provided with a third 1/4” tab on the top (on position) of the switch. Normal use is to add a jumper from the on position to the top tab to illuminate light when turned on.

  

 The switch works great when used with standard power/ground connection, e.g. landing light. When I use it in conjunction with the relay switch, the light comes on when the switch is in the off position. 	




   First, why the relay? The switch is rated for 20A . . .

   probably enough to control the pump directly.



   The third terminal is for grounding the internal LED/Resistor

   combination so that the lamp lights when the switch is closed.

   For this switch to be "relay augmented" you'll have to wire

   the pump as shown here:

 [img]cid:7.1.0.9.0.20100208135643.01e91628(at)aeroelectric.com.0[/img] 

   . . . and this is not a very elegant approach. Unfortunately

   the switch you have (like most of it's cousins) doesn't bring

   BOTH lamp leads out for independent excitation of the lamp.

   One end of the lamp is tied to the "power output" terminal

   in the assumption that one ALWAYS uses the switch barefoot

   to control power in the +supply lead.



   Bob . . .

- The Matronics AeroElectric-List Email Forum -

Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

http://www.matronics.com/Navigator?AeroElectric-List

4b765b0.jpg

Description:

Filesize:

50.12 KB

Viewed:

1596 Time(s)

longg(at)pjm.com
Guest

Posted: Mon Feb 08, 2010 2:47 pm Post subject: Question on switch wiring

Thanks Bob,  

   

Yes, the switch is overkill (or in reality, perhaps the relay is), but the switch matches the others if underutilized. I did not look hard and long enough for a 1 amp or lower with the same size/style. The pump shipped with 12 ga. wire leads and I really did not want to run a 12 ga. wire to the switch, thus the relay. The FP is rated for 7-10 amps.  

   

The FP is on the checklist but it’s one of the easy to forget items that sometimes gets left on or off. Therefore an pilot light of some kind is a nice feature.  

     

Glenn E. Long  

  

       

From: owner-aeroelectric-list-server(at)matronics.com [mailto:owner-aeroelectric-list-server(at)matronics.com] On Behalf Of Robert L. Nuckolls, III

 Sent: Monday, February 08, 2010 3:02 PM

 To: aeroelectric-list(at)matronics.com

 Subject: Re: Question on switch wiring  

  

  

   

At 12:33 PM 2/8/2010, you wrote:

 

   

I bought a SPST 12 volt lighted switch from digi-key which I would like to use as a fuel pump indicator switch.

  

 SWITCH TOGGLE ILLUM SPST 20A GRN

 SCHED B: 853650

 ECCN: EAR99

 LEAD: LEAD ALL

 ROHS:

 ROHS NONC

 CH652-ND

  

 Assumptions: My fuel pump runs via a relay switch (20 amp B & C S704-1 job).

  

  

  

 Question: The switch is provided with a third 1/4” tab on the top (on position) of the switch. Normal use is to add a jumper from the on position to the top tab to illuminate light when turned on.

  

 The switch works great when used with standard power/ground connection, e.g. landing light. When I use it in conjunction with the relay switch, the light comes on when the switch is in the off position.  



 

   First, why the relay? The switch is rated for 20A . . .

   probably enough to control the pump directly.

 

   The third terminal is for grounding the internal LED/Resistor

   combination so that the lamp lights when the switch is closed.

   For this switch to be "relay augmented" you'll have to wire

   the pump as shown here:

 [img]cid:image001.jpg(at)01CAA8E5.064AE830[/img]

   . . . and this is not a very elegant approach. Unfortunately

   the switch you have (like most of it's cousins) doesn't bring

   BOTH lamp leads out for independent excitation of the lamp.

   One end of the lamp is tied to the "power output" terminal

   in the assumption that one ALWAYS uses the switch barefoot

   to control power in the +supply lead.

 

   Bob . . .

- The Matronics AeroElectric-List Email Forum -

Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

http://www.matronics.com/Navigator?AeroElectric-List

image001.jpg

Description:

Filesize:

50.12 KB

Viewed:

1591 Time(s)

nuckolls.bob(at)aeroelect
Guest

Posted: Mon Feb 08, 2010 3:31 pm Post subject: Question on switch wiring

At 04:44 PM 2/8/2010, you wrote:

 	  Quote: 	
		  Thanks Bob,



Yes, the switch is overkill (or in reality, perhaps the relay is), 

but the switch matches the others if underutilized. I did not look 

hard and long enough for a 1 amp or lower with the same size/style. 

The pump shipped with 12 ga. wire leads and I really did not want to 

run a 12 ga. wire to the switch, thus the relay. The FP is rated for 7-10 amps.


	


  Do you have real world current values for what

  the pump needs in normal operations? Is this a

  flight pump or an aux/boost pump that is seldom

  used/needed?  7A (100 watts) is a LOT of power

  for the pumping of fuel. While your pump may be

  capable of drawing that much current at rated

  maximum volume and pressure, I've found that

  most real-world installations are much less

  demanding.



  I think it likely that you can simply wire

  the pump system with 16 awg wires through

  the un-aided switch protected by a 10A

  fuse/breaker. But you need to get some

  real numbers from somebody who's flying

  the system or the folks who engineered

  the system and have numbers.



  Alternatively, wire it all with 14AWG,

  15A breaker and leave the relay out. MUCH

  simpler and more reliable.  The built in

  lamp can be used as defined in original

  design goals.



  Bob. . .

- The Matronics AeroElectric-List Email Forum -

Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

http://www.matronics.com/Navigator?AeroElectric-List

longg(at)pjm.com
Guest

Posted: Tue Feb 09, 2010 6:35 am Post subject: Question on switch wiring

Excellent, I'm all for simplification. Before I touch it I will get the

real numbers.



Thanks Bob.



--

- The Matronics AeroElectric-List Email Forum -

Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

http://www.matronics.com/Navigator?AeroElectric-List

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