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jay(at)horriblehyde.com
Guest

Posted: Mon Sep 14, 2009 12:15 am Post subject: Filter for Hand held devices

Hi there Bob,   

   

In your Aeroelectric Connection book/ manual you provide a circuit diagram for a ‘Dual Power Conditioner “ (Figure 16.4) where you provide part numbers for the diodes and inductor components.  Would you be able to provide specifications for these instead?  I tried to search Radio Shack for the inductor part number but had no luck; plus, we have no radio shack in South   Africa so I need to be able to get the part by specification.. J  

   

Thanks  

   

Jay  

       [quote][b]

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nuckollsr

Joined: 24 Mar 2009
Posts: 95
Location: Medicine Lodge, KS

Posted: Mon Sep 14, 2009 4:28 am Post subject: Re: Filter for Hand held devices

Are you sure you need the filter? Most modern hand helds supplied with DC power input jacks and automotive cigar lighter power cords are already configured to live in the rough and tumble world of vehicular DC power systems.  The discussions on filters and firewalls in the 'Connection are intended to illustrate SOLUTIONS to noise issues should such problems arise.  It's not necessary or recommended that such devices be included as an expanded design goal.



Bob . . .

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jay(at)horriblehyde.com
Guest

Posted: Mon Sep 14, 2009 5:26 am Post subject: Filter for Hand held devices

I think that I do need one; I am using a cigarette lighter type connection

to power an Ipod power supply.  When I connect this to the Ipod no noise is

heard, but when I connect the Ipod to the radio/ intercom system I

immediately get a high pitched noise in the earphones.  I separated the

power and signal leads and the noise stayed.  I moved the power supply of

the cigarette/ Ipod charger directly to the battery and the noise stayed.  I

will still try a twisted pair on the power supply to the radio/intercom but

it seems to me that the noise is generated by the Ipod charger so I thought

that a filter might do the trick.  Perhaps even a ferrite bead on the

positive in to the radio will work.



The only other thing that I can think of is that the loop formed by the

plug->Ipod charger->Ipod audio out->radio/intercom is somehow causing the

problem; but how does one get rid of that loop- its intrinsic to the music

input?



So I am going to try all of these out but need the components for the filter

to give it a bash as well...



--

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nuckolls.bob(at)aeroelect
Guest

Posted: Mon Sep 21, 2009 12:37 pm Post subject: Filter for Hand held devices

At 08:11 AM 9/14/2009, you wrote:

 	  Quote: 	
		  



I think that I do need one; I am using a cigarette lighter type connection

to power an Ipod power supply.  When I connect this to the Ipod no noise is

heard, but when I connect the Ipod to the radio/ intercom system I

immediately get a high pitched noise in the earphones.


	


   Okay, 'high pitched' is not alternator noise. It

   MIGHT be an artifact of the dc/dc converter in your

   ipod power adapter. Try first to power the Ipod internally

   without the adapter. Does the noise go away? Try powering

   the adapter fromits own 12 battery pack NOT connected to the a/c

   in any way. A couple of el-cheeso 6v lantern batteries in

   series a good diagnostic supply.



 	  Quote: 	
		     I separated the

power and signal leads and the noise stayed.  I moved the power supply of

the cigarette/ Ipod charger directly to the battery and the noise stayed.  I

will still try a twisted pair on the power supply to the radio/intercom but

it seems to me that the noise is generated by the Ipod charger so I thought

that a filter might do the trick.  Perhaps even a ferrite bead on the

positive in to the radio will work.



The only other thing that I can think of is that the loop formed by the

plug->Ipod charger->Ipod audio out->radio/intercom is somehow causing the

problem; but how does one get rid of that loop- its intrinsic to the music

input?


	


    It's most likely to be a ground loop issue which will be

    re-enforced or denied by the above experiments.



    In any case, it's almost a certainty that filtering

    is not solution for root cause.



    We may have to incorporate an isolation transformer

    where audio from your Ipod goes to one winding and

    audio to the ship's system is taken from the other

    winding. See:



http://www.radioshack.com/product/index.jsp?productId 103994

    Bob . . .

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ianxbrown

Joined: 16 May 2009
Posts: 80

Posted: Mon Sep 21, 2009 1:22 pm Post subject: Filter for Hand held devices

Just for information of those on the list, I recently had a faulty 12V charger on an AV8OR.  The manufacturer willingly changed it.  The symptoms were more your conventional white noise type static, like a very weak radio signal - there when charging the AV8OR, gone when not.   It interfered with radio reception in the car and in the aircraft.  I'm not proposing it as the cause of the IPOD problem below, just a useful data point.  Faulty chargers do indeed seem capable of generating interference but not, in my case, a high pitched noise.

 Ian Brown

 Bromont, Quebec

 

  	  Quote: 	
		    	  Quote: 	
		  

 	  Quote: 	
		  The only other thing that I can think of is that the loop formed by the

plug->Ipod charger->Ipod audio out->radio/intercom is somehow causing the

problem; but how does one get rid of that loop- its intrinsic to the music

input?


	


    It's most likely to be a ground loop issue which will be

    re-enforced or denied by the above experiments.



    In any case, it's almost a certainty that filtering

    is not solution for root cause.



    We may have to incorporate an isolation transformer

    where audio from your Ipod goes to one winding and

    audio to the ship's system is taken from the other

    winding. See:

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nuckolls.bob(at)aeroelect
Guest

Posted: Mon Sep 21, 2009 8:32 pm Post subject: Filter for Hand held devices

At 04:18 PM 9/21/2009, you wrote:

 	  Quote: 	
		  Just for information of those on the list, I recently had a faulty 

12V charger on an AV8OR.  The manufacturer willingly changed 

it.  The symptoms were more your conventional white noise type 

static, like a very weak radio signal - there when charging the 

AV8OR, gone when not.   It interfered with radio reception in the 

car and in the aircraft.  I'm not proposing it as the cause of the 

IPOD problem below, just a useful data point.  Faulty chargers do 

indeed seem capable of generating interference but not, in my case, 

a high pitched noise.


	


    The modern DC/DC converter technology has become smaller

    and more efficient as the components became available to

    operate at high and higher frequencies. The DC to DC

    converters that we used in the Cessna Nav/Com 300 in 1965

    ran at about 1 Khz . . . and had relatively benign

    RF interference potential. That little nugget of electronics

    that exists in the cigar lighter plug on your ipod or cell

    phone charger probably operates at 1000 to 2000 times higher

    frequency. These guys are much more likely to become

    noise emitters in the AM radio band. I've had

    several devices that I had to throw away and substitute

    another brand.



    Bob . . .

        Bob . . .



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

        ( . . .  a long habit of not thinking   )

        ( a thing wrong, gives it a superficial )

        ( appearance of being right . . .       )

        (                                       )

        (                  -Thomas Paine 1776-  )

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

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jay(at)horriblehyde.com
Guest

Posted: Mon Sep 21, 2009 10:16 pm Post subject: Filter for Hand held devices

Thanks Bob,



That does make sense; I had isolated it to the dc/dc converter in the same

manner that you suggest here- by powering the device internally.  I knew

that it wasn't alternator noise since I was running off the a/c battery

only.  I then found out that the same noise has presented itself on another

installation that I did, so it couldn't be installation specific.  There the

owner simply let the Ipod charge up and then disconnected it from the system

and played the music into the audio system using the Ipod internal battery.



I'll try and get an isolation transformer here and see what effect that has;

it is simply a transformer with a 1:1 winding ratio?



Jay

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jay(at)horriblehyde.com
Guest

Posted: Tue Sep 22, 2009 12:22 am Post subject: Filter for Hand held devices

Duh.. scratch that question- its says exactly that on the Radio Shack page;

just noticed now...

I'll provide some feedback when I get the transformer



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