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Mag Timing

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jgh2(at)charter.net
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Posted: Wed Jun 22, 2011 2:22 am Post subject: Mag Timing

See the low cost magneto timing kit at www.MagnetoTimer.com.It works well and can be built and tested quickly.

Jack Haviland

RV-6A 

 [quote][b]

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nuckolls.bob(at)aeroelect
Guest

Posted: Wed Jun 22, 2011 5:53 am Post subject: Mag Timing

At 05:19 AM 6/22/2011, you wrote:

  	  Quote: 	
		  See the low cost magneto timing kit at www.MagnetoTimer.com.

 It works well and can be built and tested quickly. 	


   The "magic" behind a magneto timing light is the

   device's ability to detect points opening and

   closing when paralleled with a VERY low resistance

   of a magneto's p-lead winding.



   The DC resistance measured with points-open

   is low and goes lower when points close . . .

   difficult to see with the garden variety

   ohmmeter. The legacy mag-timer used a

   buzzer to generate an AC signal (not unlike

   the Shower-of-Sparks buzzer) to excite

   the p-lead circuit. 

 [img]cid:.0[/img]



   When the mag points are closed, there's a dead

   short across the primary of the transformer and

   no signal is detected by the neon lamp. When the

   points open, the dc resistance rises slightly

   but the inductive value rises greatly. The small

   AC component that appears between the test leads

   is amplified by the transformer to a value sufficient

   to light the neon lamp. This is the legacy "buzz box".



   Additionally, one could generally hear a change in

   the characteristic of the sound from the buzzer

   when the points open.



   You can still build this device from readily

   available parts. For a compendium of magneto

   timing devices see:



  http://www.aeroelectric.com/articles/Magneto_Timing/



   There's a dozen ways to "skin this cat." I've

   not tried it, but I'll bet the low-ohms adapter

   we developed would detect point-opening/closure

   on a mag. I'm certain that the new and improved

   version (coming out shortly) would do it.



   The directory cited above shows Jim Wier's

   approach to exciting the open p-lead with a

   2 kHz signal and then detecting the rise in

   circuit impedance as points open to light

   some leds and give an audible indication.



   A google search on 'magneto timing' will

   yield dozens of articles and tools . . . each

   of which is cited as a better way to skin

   the cat. In fact, all such tools from the

   lowly buzz-box to the most sophisticated

   micro-processor based gee-whiz work as

   advertised . . .



   Sometimes, the best way to drive a nail

   is with a hammer.



 

   Bob . . .

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