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starter warning light?

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Erich_Weaver(at)URSCorp.c
Guest

Posted: Thu Jan 18, 2007 9:24 am Post subject: starter warning light?

A friend recommended adding a warning light to my panel that would simply

indicate whether there was power present at the starter.  Is this providing

any real benefit? I presume the warning light would  be lit for the few

seconds when I push my push-to-start button, but also when the button  was

inadvertently stuck in the on position or the starter contactor was stuck

closed.  Are a stuck switch or contactor likely enough to warrant this

warning light?  I have vague memories of a starter run-on issue, but

perhaps that is a separate issue all together?  Gotta re-read the

'Connection before I forget all the great stuff I learned.



Erich Weaver

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nuckollsr(at)cox.net
Guest

Posted: Thu Jan 18, 2007 10:12 am Post subject: starter warning light?

At 09:23 AM 1/18/2007 -0800, you wrote:



 	  Quote: 	
		  

A friend recommended adding a warning light to my panel that would simply

indicate whether there was power present at the starter.  Is this providing

any real benefit? I presume the warning light would  be lit for the few

seconds when I push my push-to-start button, but also when the button  was

inadvertently stuck in the on position or the starter contactor was stuck

closed.  Are a stuck switch or contactor likely enough to warrant this

warning light?  I have vague memories of a starter run-on issue, but

perhaps that is a separate issue all together?  Gotta re-read the

'Connection before I forget all the great stuff I learned.


	


   Starter "run-on" and "sticking" are two separate issues. Run-on

   is a phenomenon unique to permanent magnet motors on starters

   that under certain wiring configurations will cause a delayed

   dis-engagement of the pinion gear after the engine catches and

   the starter button is released.



   One solution to this problem is illustrated at:



http://www.aeroelectric.com/PPS/Engine/Starter/PM_Starter_w_RunOn_Relay.pdf



   The value of a STARTER ENGAGED light is to detect a stuck

   starter button and/or stuck starter contactor. These events

   are rare but allowed to proceed without detection is always

   expensive.



   You can use an LED. Put the LED's ballasting resistor right

   at the starter main power terminal. Incorporate into the

   wire using techniques described in:



http://www.aeroelectric.com/articles/Homeless/Homeless_Components.htm



   Put a diode across the LED in the reverse direction to protect

   from small reverse votlage transients that are ALWAYS hard

   on LEDs. See:



http://www.aeroelectric.com/Pictures/Schematics/Starter_Engaged_Warning_Lt.pdf



   It's a toss up. Adding the light is relatively easy, inexpensive

   and doesn't add much weight to the airplane. It's easier to add

   while building the airplane than to add it after it's finished.

   If you're un-decided, at least pull the wire in and cap it off

   to make it easier to add later.



   Another instance of value added warning lights for starter

   control systems is illustrated at:



http://www.aeroelectric.com/PPS/Engine/Starter/24V_Starter_14V_System.pdf



   Here we see a means by which a 24 volt starter can be

   serviced in 14 volt airplane. The lights are designed to

   detect a stuck contactor in the series/parallel changeover

   contactors. An unattended sticking of one of these relays

   causes BIG fault currents to flow when buttons are pushed.



   Bob . . .



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

      < What is so wonderful about scientific truth...is that >

      < the authority which determines whether there can be   >

      < debate or not does not reside in some fraternity of   >

      < scientists; nor is it divine. The authority rests     >

      < with experiment.                                      >

      <                            --Lawrence M. Krauss       >

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

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recapen(at)earthlink.net
Guest

Posted: Thu Jan 18, 2007 10:41 am Post subject: starter warning light?

Bob,



On the B&C website, the documentation for the starter relay says you can use the I terminal as a starter on light source.  



Is this different than the solutions you have described below?



Thanks,

Ralph



--

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nuckollsr(at)cox.net
Guest

Posted: Thu Jan 18, 2007 11:03 am Post subject: starter warning light?

At 01:39 PM 1/18/2007 -0500, you wrote:



 	  Quote: 	
		  

<recapen(at)earthlink.net>



Bob,



On the B&C website, the documentation for the starter relay says you can 

use the I terminal as a starter on light source.



Is this different than the solutions you have described below?


	


   If your starter contactor HAS and "I" terminal, it can

   be used for this purpose. I show the "generic" version

   because it works with any contactor . . . INCLUDING the

   one built onto the starter whether or not it incorporates

   an "I" terminal.



   Bob . . .

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recapen(at)earthlink.net
Guest

Posted: Thu Jan 18, 2007 11:36 am Post subject: starter warning light?

Thanks



----->   If your starter contactor HAS and "I" terminal, it can

 	  Quote: 	
		     be used for this purpose.

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Erich_Weaver(at)URSCorp.c
Guest

Posted: Thu Jan 18, 2007 2:11 pm Post subject: starter warning light?

OK, got it: starter run-on and sticking are different issues.  But assuming

I install the warning light and subsequently have a starter run-on

occurrence, will the warning light be on while the run-on is occurring?  An

individual suggested to me off-list that if  the starter gear is stuck in

the engaged position and the engine is running (push-to-start button

released and starter contactor open), the starter motor could act as a

generator and produce some current.  If this is the case, it would seem

that a  warning light that stayed on a little longer than the short period

my push to start button was in use could potentially be warning me of the

dreaded run-on condition instead of just the stuck contactor or stuck

starter button.  Added value or just wishful thinking?



Erich Weaver

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nuckollsr(at)cox.net
Guest

Posted: Fri Jan 19, 2007 5:16 am Post subject: starter warning light?

At 02:09 PM 1/18/2007 -0800, you wrote:



 	  Quote: 	
		  

OK, got it: starter run-on and sticking are different issues.  But assuming

I install the warning light and subsequently have a starter run-on

occurrence, will the warning light be on while the run-on is occurring?


	


    Yes. While the PM motor is spinning down the voltage generated

    by the rotating armature will keep the light lit. As the armature

    comes to a stop the light will go out.



 	  Quote: 	
		    An

individual suggested to me off-list that if  the starter gear is stuck in

the engaged position and the engine is running (push-to-start button

released and starter contactor open), the starter motor could act as a

generator and produce some current.


	


    A much fertilize myth. Starters have over-run clutches. The engine

    CANNOT be allowed to 'push' the starter under any circumstances.

    Consider that a highly geared starter armature is spinning at thousands

    of RPM while cranking the engine at perhaps 300 rpm. When the engine

    starts, it jumps up to 1000-1500 rpm. This 3 to 5 times increase in

    speed cannot be allowed to impress on the starter's gears and armature.

    The forces applied to gear teeth place them at risk. Spinning the

    armature places winding and commutator at risk for damage due to

    centrifugal forces.



 	  Quote: 	
		     If this is the case, it would seem

that a  warning light that stayed on a little longer than the short period

my push to start button was in use could potentially be warning me of the

dreaded run-on condition instead of just the stuck contactor or stuck

starter button.  Added value or just wishful thinking?


	


    The condition we've called "run-on" is poorly named. It's really

    "delayed disengagement" do to currents circulating in the pinion

    gear engagement solenoid that are being generated in a slowing

    armature spinning in a permanent magnetic field. I've never personally

    observed this event but it's my understanding that it lasts perhaps

    3-5 seconds.



    The "run-on" condition is not particularly stressful on the

    starter . . . because of the over-run clutch cited. Assuming

    (1) you wire your starter engaged light so as to sense voltage

    at the starter motor power terminal and (2) it's a PM starter and

    (3) you HAVE installed the relay intended to prevent delayed

    disengagement then, you would STILL observe a fading STARTER

    ENGAGED indication from the annunciator as the starter motor spins

    down. This happens in spite of the fact that the relay has broken

    the circuit responsible for delayed disengagement.



    The light has value in that it shows when voltage is present

    at the starter motor terminals at times when it is not expected

    or desirable. It will also demonstrate the voltage generating

    quality of a PM motor as it spins down after being disconnected

    from the battery.



    Bob . . .

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