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oil pressure warn logic

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rshannon

Joined: 05 Sep 2007
Posts: 62

Posted: Mon May 05, 2008 11:14 am Post subject: oil pressure warn logic

Here's a puzzle. It may be a "can't get there from here" or a "why bother" situation, but I know some of you listers love a challenge. 



I have a B&C S8012 oil pressure switch, where the N.C. contact is wired to an oil pressure warning LED. (See http://www.bandc.biz/S8012dwg.pdf)  I also have an ACS OFF-L-R-BOTH key switch for the mags (separate START button) and an S700-2-10 master switch. The issue is that I would like the oil pressure warning LED to operate only when the ACS key switch is not OFF, e.g., when it's in any of the L-R-BOTH positions.  The reason is that I don't want the oil pressure warning light ON when I'm just running the panel during engine off ground ops.  I plan a separate master ON nag LED, also wired through the N.C. contact.

 

In short, I'd like to distinguish between A) master only ON, and B) master AND key switch ON.



It's apparent that I need to incorporate the logic of the key switch (see Z-27 logic table) into the low oil pressure warning LED circuit somehow but I'm bamboozled as to how to do it, especially in a way that won't defeat the purpose of the mag switch(s). Of course, I'd rather not add another relay, but additional diode switching logic might be OK.

 

Ron



  [quote][b]

mprather(at)spro.net
Guest

Posted: Mon May 05, 2008 12:33 pm Post subject: oil pressure warn logic

If course, you could get rid of the key switch in favor of a couple of

simple toggle switches.  One of the toggle switches could have an extra

pole which would defeat the OP light when off.  Easy.



I don't think the ACS key switch has any unused poles.  I don't see a way

to control the OP light with the key switch without adding some fail modes

to the magneto operation.  And needless complexity.



As was mentioned by a lister a while back concerning controlling the Hobbs

by means of monitoring alternator operation, a similar method could be

used to control the OP warning light.



With a couple of components, you could add a "defeat" circuit which would

allow suppressing the OP light operation by means of a momentary push

button.  Turn the master on, press the OP warning "defeat" button, and the

light goes out.  Next time the master is cycled, the OP warning functions

as expected.



Finally, why are you concerned about the OP warning being on when with

engine-off operations?  It probably won't burn as much power as anything

else in the panel..  I guess that fits into the "why bother" response

category...  

Regards,



Matt-



 	  Quote: 	
		   Here's a puzzle. It may be a "can't get there from here" or a "why bother"

 situation, but I know some of you listers love a challenge. 



 I have a B&C S8012 oil pressure switch, where the N.C. contact is wired to

 an oil pressure warning LED. (See http://www.bandc.biz/S8012dwg.pdf)  I

 also

 have an ACS OFF-L-R-BOTH key switch for the mags (separate START button)

 and

 an S700-2-10 master switch. The issue is that I would like the oil

 pressure

 warning LED to operate only when the ACS key switch is not OFF, e.g., when

 it's in any of the L-R-BOTH positions.  The reason is that I don't want

 the

 oil pressure warning light ON when I'm just running the panel during

 engine

 off ground ops.  I plan a separate master ON nag LED, also wired through

 the

 N.C. contact.



 In short, I'd like to distinguish between A) master only ON, and B) master

 AND key switch ON.



 It's apparent that I need to incorporate the logic of the key switch (see

 Z-27 logic table) into the low oil pressure warning LED circuit somehow

 but

 I'm bamboozled as to how to do it, especially in a way that won't defeat

 the

 purpose of the mag switch(s). Of course, I'd rather not add another relay,

 but additional diode switching logic might be OK.



 Ron

rshannon

Joined: 05 Sep 2007
Posts: 62

Posted: Mon May 05, 2008 1:36 pm Post subject: oil pressure warn logic

Thanks, Matt. All points well taken.



One reason to have that light OFF during engine off ground ops would be to make it more palatable to use a blinking LED. After due deliberations, I committed to the key switch some time back. As you point out, it would have been easy with mag toggles. A latching defeat switch, perhaps with an auto timeout in addition to the master cycle reset you suggest, is a possibility.



Of course, the oil pressure warn is critical, and mandates a KISS architecture. No doubt, it's my inclination to complicate it that deserves a defeat switch. 



Ron



On Mon, May 5, 2008 at 1:29 PM, Matt Prather <mprather(at)spro.net (mprather(at)spro.net)> wrote:

 [quote]--> AeroElectric-List message posted by: "Matt Prather" <mprather(at)spro.net (mprather(at)spro.net)>

  

 If course, you could get rid of the key switch in favor of a couple of

 simple toggle switches.  One of the toggle switches could have an extra

 pole which would defeat the OP light when off.  Easy.

 

 I don't think the ACS key switch has any unused poles.  I don't see a way

 to control the OP light with the key switch without adding some fail modes

 to the magneto operation.  And needless complexity.

 

 As was mentioned by a lister a while back concerning controlling the Hobbs

 by means of monitoring alternator operation, a similar method could be

 used to control the OP warning light.

 

 With a couple of components, you could add a "defeat" circuit which would

 allow suppressing the OP light operation by means of a momentary push

 button.  Turn the master on, press the OP warning "defeat" button, and the

 light goes out.  Next time the master is cycled, the OP warning functions

 as expected.

 

 Finally, why are you concerned about the OP warning being on when with

 engine-off operations?  It probably won't burn as much power as anything

 else in the panel..  I guess that fits into the "why bother" response

 category...  

 

 

 Regards,

 

 Matt-

 [b]

nuckolls.bob(at)cox.net
Guest

Posted: Tue May 06, 2008 5:27 am Post subject: oil pressure warn logic

At 02:29 PM 5/5/2008 -0700, you wrote:



 	  Quote: 	
		  Thanks, Matt. All points well taken.



One reason to have that light OFF during engine off ground ops would be to 

make it more palatable to use a blinking LED. After due deliberations, I 

committed to the key switch some time back. As you point out, it would 

have been easy with mag toggles. A latching defeat switch, perhaps with an 

auto timeout in addition to the master cycle reset you suggest, is a 

possibility.



Of course, the oil pressure warn is critical, and mandates a KISS 

architecture. No doubt, it's my inclination to complicate it that deserves 

a defeat switch. 



Ron


	


   Do you have a low voltage warning light? Does it not flash?

   The reason for flashing lights is to get attention to an

   urgent matter. Another advantage of flashing lights is to

   remind you to turn the master switch(es) off after engine

   shutdown.



   I'm curious as to the driver behind efforts to defeat the

   ideas that drove the original design goals for these lights.



   Bob . . .

user9253

Joined: 28 Mar 2008
Posts: 1920
Location: Riley TWP Michigan

Posted: Tue May 06, 2008 7:03 am Post subject: oil pressure warn logic

Ron,

 You could check the continuity of the unused terminals LR and BO on the  back of the ACS key switch.  Check from LR and BO to BAT and to GROUIND and  to terminals R and L with the switch in different positions.  Report your  findings back here and maybe someone can use that information to help you.   Even if those unused terminals are of no use for your application, knowing how  they are wired is useful information that could help others.  This website  http://www.aircraftspruce.com/pdf/2008Individual/Cat08448.pdf has  a pinout of the back of the switch, but there is no schematic to show exactly  how the switch is wired internally.  Adding a circuit component that  disables the low pressure warning light introduces a failure point that could  prevent the light from warning you when needed.

 Joe

   [quote][b]

_________________
Joe Gores

nuckolls.bob(at)cox.net
Guest

Posted: Tue May 06, 2008 9:30 am Post subject: oil pressure warn logic

At 10:55 AM 5/6/2008 -0400, you wrote:



 	  Quote: 	
		  Ron,

You could check the continuity of the unused terminals LR and BO on the 

back of the ACS key switch.  Check from LR and BO to BAT and to GROUIND 

and to terminals R and L with the switch in different positions.  Report 

your findings back here and maybe someone can use that information to help 

you.  Even if those unused terminals are of no use for your application, 

knowing how they are wired is useful information that could help 

others.  This website 

<http://www.aircraftspruce.com/pdf/2008Individual/Cat08448.pdf>http://www.aircraftspruce.com/pdf/2008Individual/Cat08448.pdf 

has a pinout of the back of the switch, but there is no schematic to show 

exactly how the switch is wired internally.  Adding a circuit component 

that disables the low pressure warning light introduces a failure point 

that could prevent the light from warning you when needed.

Joe


	


Functionality of the internal workings of the classic off-l-r-both-start

switch is described at:



http://www.aeroelectric.com/PPS/Adobe_Architecture_Pdfs/Z26-27K.pdf





        Bob . . .



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

        ( . . .  a long habit of not thinking   )

        ( a thing wrong, gives it a superficial )

        ( appearance of being right . . .       )

        (                                       )

        (                  -Thomas Paine 1776-  )

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

rshannon

Joined: 05 Sep 2007
Posts: 62

Posted: Tue May 06, 2008 9:33 am Post subject: oil pressure warn logic

On Tue, May 6, 2008 at 6:24 AM, Robert L. Nuckolls, III <nuckolls.bob(at)cox.net (nuckolls.bob(at)cox.net)> wrote:

 	  Quote: 	
		   --> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <nuckolls.bob(at)cox.net (nuckolls.bob(at)cox.net)>

 

 At 02:29 PM 5/5/2008 -0700, you wrote:

 

  	  Quote: 	
		   Thanks, Matt. All points well taken.

 

 One reason to have that light OFF during engine off ground ops would be to make it more palatable to use a blinking LED. After due deliberations, I committed to the key switch some time back. As you point out, it would have been easy with mag toggles. A latching defeat switch, perhaps with an auto timeout in addition to the master cycle reset you suggest, is a possibility.

  

 Of course, the oil pressure warn is critical, and mandates a KISS architecture. No doubt, it's my inclination to complicate it that deserves a defeat switch. 

 

 Ron

 	
 



   Do you have a low voltage warning light? Does it not flash?

   The reason for flashing lights is to get attention to an

   urgent matter. Another advantage of flashing lights is to

   remind you to turn the master switch(es) off after engine

   shutdown.

 

   I'm curious as to the driver behind efforts to defeat the

   ideas that drove the original design goals for these lights.

 

   Bob . . . 	


Bob, I thought I had explained the driver -- not necessarily a sufficient  one -- to allow ground ops (programming GPS, etc.) without having the oil pressure warn light blinking away. (Yes, my LV warn light will blink, and the same issue may apply when not on ground power.)

 

I did concede at the outset and again above that this concern may not be important enough to change the circuit, logic, etc. Just a puzzle that I thought worthy of discussion if, and only if, it could be solved safely and reliably.

 

Ron



  [quote][b]

rshannon

Joined: 05 Sep 2007
Posts: 62

Posted: Tue May 06, 2008 9:35 am Post subject: oil pressure warn logic

On Tue, May 6, 2008 at 7:55 AM, Joe <fran5sew(at)banyanol.com (fran5sew(at)banyanol.com)> wrote:

 	  Quote: 	
		          Ron,

 You could check the continuity of the unused terminals LR and BO on the  back of the ACS key switch.  Check from LR and BO to BAT and to GROUIND and  to terminals R and L with the switch in different positions.  Report your  findings back here and maybe someone can use that information to help you.   Even if those unused terminals are of no use for your application, knowing how  they are wired is useful information that could help others.  This website  http://www.aircraftspruce.com/pdf/2008Individual/Cat08448.pdf has  a pinout of the back of the switch, but there is no schematic to show exactly  how the switch is wired internally.  Adding a circuit component that  disables the low pressure warning light introduces a failure point that could  prevent the light from warning you when needed.

 Joe



	




The key switch model without START doesn't have those terminals. Just GND, L and R.



I realize this proposal could introduce failure points, and thought I had already acknowledged that, though perhaps not enough. Surely the fact that some proposal may introduce failure points if not done right is not a reason to explore possible ways to do it right.

 

Ron



  [quote][b]

rshannon

Joined: 05 Sep 2007
Posts: 62

Posted: Tue May 06, 2008 9:49 am Post subject: oil pressure warn logic

On Tue, May 6, 2008 at 10:26 AM, Robert L. Nuckolls, III <nuckolls.bob(at)cox.net (nuckolls.bob(at)cox.net)> wrote:

 	  Quote: 	
		   --> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <nuckolls.bob(at)cox.net (nuckolls.bob(at)cox.net)>

 

...

 Functionality of the internal workings of the classic off-l-r-both-start

 switch is described at:

 

 http://www.aeroelectric.com/PPS/Adobe_Architecture_Pdfs/Z26-27K.pdf

 

 

 

 

        Bob . . .

 	


Understood. I referenced Z-27 in the first post in this thread.



Ron

  [quote][b]

user9253

Joined: 28 Mar 2008
Posts: 1920
Location: Riley TWP Michigan

Posted: Wed May 07, 2008 10:36 am Post subject: oil pressure warn logic

Ron,

  

 Looking at the schematic that Bob K provided on Z-26, there are no unused  contacts on the key switch.  Connecting to the left or right mag wires is a  bad idea because doing so might disable the magneto.  Here is a suggestion:  Tape a piece of reflective tape to the key.  Aim an optical IR beam at the  key so that the beam will reflect to a receiver when the key is in the off  position.  When the reflected beam is received, the low oil pressure  warning light will be disabled.  It sounds complicated but I am sure that  there are off the shelf parts available to easily accomplish this.  Perhaps  someone knowledgeable in solid state circuitry can help you.

 Joe

   [quote][b]

_________________
Joe Gores

rshannon

Joined: 05 Sep 2007
Posts: 62

Posted: Wed May 07, 2008 10:53 am Post subject: oil pressure warn logic

ROTFL !  I knew sooner or later somebody would come through with an elegant, failsafe solution!



Ron

On Wed, May 7, 2008 at 11:32 AM, Joe <fran5sew(at)banyanol.com (fran5sew(at)banyanol.com)> wrote:

 [quote]       Ron,

  

 Looking at the schematic that Bob K provided on Z-26, there are no unused  contacts on the key switch.  Connecting to the left or right mag wires is a  bad idea because doing so might disable the magneto.  Here is a suggestion:  Tape a piece of reflective tape to the key.  Aim an optical IR beam at the  key so that the beam will reflect to a receiver when the key is in the off  position.  When the reflected beam is received, the low oil pressure  warning light will be disabled.  It sounds complicated but I am sure that  there are off the shelf parts available to easily accomplish this.  Perhaps  someone knowledgeable in solid state circuitry can help you.

 Joe



[b]

mprather(at)spro.net
Guest

Posted: Wed May 07, 2008 11:05 am Post subject: oil pressure warn logic

I little Rube Goldberg-ian, but I like it..  



A crude optical encoder..

Matt-



 	  Quote: 	
		   Ron,



 Looking at the schematic that Bob K provided on Z-26, there are no unused

 contacts on the key switch.  Connecting to the left or right mag wires is

 a bad idea because doing so might disable the magneto.  Here is a

 suggestion: Tape a piece of reflective tape to the key.  Aim an optical IR

 beam at the key so that the beam will reflect to a receiver when the key

 is in the off position.  When the reflected beam is received, the low oil

 pressure warning light will be disabled.  It sounds complicated but I am

 sure that there are off the shelf parts available to easily accomplish

 this.  Perhaps someone knowledgeable in solid state circuitry can help

 you.

 Joe

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