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paulm(at)olypen.com
Guest

Posted: Sun Sep 11, 2011 10:33 am Post subject: ...failure mode

Bob's scope digital sampling is very slow sampling as usual. The peak inrush 

current is basically current limited to the power supply and wiring and 

switcher resistance. He shows one sample at over 30 amps and who knows what 

the peak current is. HID do have issues with wig wag and below I got info 

from a pilot who solved it.



Your current limiter as you mentioned would limit this way down and produce 

a great increase in lifetime.



However if one uses the H3 bulbs there is one type of HID supply that works 

well with wig wag while most do not. The H3 is a drop in for most Vans and 

other wing mountes aircraft. There is also a replacement bulb for the round 

lights using the same ballast that should work well.. Then you need to use a 

specific toroid filter on the lines and a no bounce switch contact (solid 

state).



I got the info from a suscessful fligher months ago and the parts are cheep 

also Like at the time 30 for a system. NOT all hid systems will work wig wag 

as the supply simply dies soon



I can go back and try to find the link if you are interested. I will not 

post to Bob's list ever!!!!



Pardon the smelling but my chkr is off as comp[uter crash and ng backup is 

back and running but word is the spel checker and its not reinstalled



Paul

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nuckolls.bob(at)aeroelect
Guest

Posted: Mon Sep 12, 2011 4:24 am Post subject: ...failure mode

At 01:29 PM 9/11/2011, you wrote:

 	  Quote: 	
		  



Bob's scope digital sampling is very slow sampling as usual.


	


   Really? As usual? Exactly what was the sampling rate

   for the data depicted? What is your basis for the assertion?

   Inquiring minds want to know.



 	  Quote: 	
		  The peak inrush current is basically current limited to the power 

supply and wiring and switcher resistance. He shows one sample at 

over 30 amps and who knows what the peak current is.


	


   Is that the point? The purpose for producing that plot

   was to demonstrate that the incandescent lamp under study

   (I think it was an automotive halogen) does not cool

   sufficiently between wig-wag flashes to produce a series

   of inrush currents even close to what is produced by

   the first, cold start.



   <snip>



 	  Quote: 	
		  I got the info from a suscessful fligher months ago and the parts 

are cheep also Like at the time 30 for a system. NOT all hid systems 

will work wig wag as the supply simply dies soon



I can go back and try to find the link if you are interested. I will 

not post to Bob's list ever!!!!


	


   . . .  yet here you are!

        Bob . . .

                    ////

                   (o o)

    ===========o00o=(_)=o00o=========

    < Go ahead, make my day . . .   >

    < show me where I'm wrong.      >

    =================================

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paulm(at)olypen.com
Guest

Posted: Mon Sep 12, 2011 9:24 am Post subject: ...failure mode

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nuckolls.bob(at)aeroelect
Guest

Posted: Mon Sep 12, 2011 1:00 pm Post subject: ...failure mode

 	  Quote: 	
		  My comments were intended to be private and addressed what I 

understood was the suggested cause of short Halogen auto lights. The 

data you showed and my personal experience is the initial ON spike 

does NOT shorten the life and your data shows wig wag surely does 

NOT have a significant effect based on heating and cooling from wig 

wag vs no wig wag after the initial ON pulse as there is no 

significant inrush on later ON pulses.


	


    My data shows the cold-start transient is typical

    of incandescent lamps. The data further shows that

    the initial current draw on subsequent on-cyles is

    absent that transient because the filament doesn't

    have time to cool down between cycles. The data

    says nothing about heating and cooling cycles.



    Heating and cooling cycles are directly related to

    light output which ranges from very dim to full bright

    which must be a transition of several thousand degrees

    and is totally unrelated to the presence or lack of

    an inrush event.



 	  Quote: 	
		  >>Bob's scope digital sampling is very slow sampling as usual.


	


 	  Quote: 	
		   >   Really? As usual? Exactly what was the sampling rate

>   for the data depicted? What is your basis for the assertion?

>   Inquiring minds want to know.



Well Bob surely you know. You say its a TDS 220 which is advertised 

as a 2 channel 100 mhz with sampling rates AS FAST AS 1GS/s; But 

that applies only for a fast sweep speed as the line buffer is 

limited to 2500 samples per line or one sample every MS (in the 

above sample) far below what is needed to determine the initial 

surge current width and peak to get the energy produced into the 

bulb. Further there is HUGE NOISE on top of the signal from 

apparently a defective setup. Further it (Sampling) is too slow to 

characterize the wig wag ON inrush current spikes but it does imply 

the inrush is small negating wig wag as a factor in bulb life.


	


    But during the discussions which accompanied the

    plot in question, we weren't really concerned

    with specifics of the inrush transients which

    by the way, were measured at other sweep settings

    but not included as not being germane to the

    discussion.



    And yes, I noted the noise present but didn't have

    time to clean it up as again, the point being made

    was to show the huge differences in lamp switching

    transients between cold start and subsequent flashes.



 	  Quote: 	
		  Its generally accepted in the industry one needs a MINIMUM sample 

rate of 10 times the expected pulse width to characterize a 

repetitive pulse and higher for a one shot event. In digital 

sampling scopes the line buffer is critical in determing the true 

sampling rate NOT the advertised sampling rate for slower sweep rates


	


    No claims are being made to the contrary.

    I think I've got the fast plots in the

    archives. If you want to discuss transient

    specifics, we can do that too. As I recall,

    the fast plots also carried the signature

    of flasher relay contact bounce and were

    not even useful to the discussion du jour.



 	  Quote: 	
		  Thus we can determine the inrush pulse is between 1 and 2 MS with a 

peak of at least 31+ amps Who knows how much the true peak current 

might be but that info is not known as the detailed setup is not 

discussed. Further the next 1 MS sample is at least 15 amps followed 

by a 10 amp sample.


	


    Yes . . . but no claims were made as to the

    inrush specifics . . . either when that plot

    was published nor in the discussions that

    started this tread.



 	  Quote: 	
		  While there is no significant repeating inrush an inrush limiter 

would stop the initial inrush and extens lamp life a point not 

noticed in the discussion as I recall.


	


    Possibly . . . but I'm unaware of any commercially

    produced vehicle that includes such inrush limiters

    on headlights . . . but I don't follow that market

    closely. I believe I was the first designer in Wichita

    to include an inrush limiter on an airplane. I put one

    on the nose gear mounted taxi light of the GP180. It went

    onto the first three prototypes but was removed when no

    definitive data  could be offered as to return on investment.

    The only thing we could demonstrate is a reduction in the flashing

    of other lights when the nose gear light was turned on.

    Same thing happened with landing lights. The reliability

    guys didn't want inrush limiters on those either due to

    lack of data for return on investment and suppression of

    reliability due to added parts.



    Later I discovered that keep-warm circuits for tungsten

    filaments on high vibration mounts had a far greater benefit

    for bulb life than inrush limiting. Never had an opportunity

    to explore that in a T/C aircraft as my job moved out of that

    arena when I went to the Targets Group.



 	  Quote: 	
		  Note sampling rate is not the average value during the sample time 

its a very short time period every  1 MS as the value must be 

captured and processed before the next sample period. Basically what 

you see is a very small sample time period being taken every 1 MS 

The tek data sheet for the scope suggests the sample period is a 

very small part of 1 MS in this case thus perhaps 99+% of the time 

the data value being sampled could be far away from the sample snap 

shot on average.



Sadly sampling scopes are easilly misunderstood when it comes to 

specifications and what is implied is often far from general truth 

for other than the specificaed setup conditions



After the initial pulse ther is so much "NOISE" on the data its 

basically impossible to determine if there is any following peaks in 

the ON current.



Not only is there 4-5 amps of noise but there is a lower frequency 

of noise implied suggestion low frequenct ripple even in the ground 

along with high frequency noise. This suggests a bad setup coupled 

with perhaps a switching power supply VS a batttery as the source of power.


	


    No, it was just an RG battery. There's a 5KW AM

    broadcast station 1 mile from the Wichita house

    that is never entirely absent from test data.

    I've suffered both the effects of 1.3Mhz carrier

    and demodulated program material.



    I didn't have time to chase it out that day

    but my lab in Medicine Lodge is entirely clean

    of such interference. I'll re-plot and publish both

    the fast and slow data for the website archive.

    It is not good that data be mis-interpreted as

    to significance or the point being made.



    Bob . . .

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william_slaughter(at)att.
Guest

Posted: Mon Sep 12, 2011 6:33 pm Post subject: ...failure mode

Promises, promises.

Have at it! as I will not post again unless I make another mistake in 

addressing posts. Nor will I reply to any further comments



Paul



 	  Quote: 	
		  



        Bob . . .

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