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Bob McC

Joined: 09 Jan 2006
Posts: 258
Location: Toronto, ON

Posted: Sun Apr 15, 2012 1:11 pm Post subject: Looking for suggestions

Dan;  

   

There is no way for a capacitor to attain a voltage higher than that which was used to charge it. The camera is a bad example because it more closely resembles your strobes whose capacitor might indeed be several hundred volts, but it is not charged by directly applying battery voltage. There is electronic circuitry involved which can theoretically apply any voltage which the designer of the circuit decides he needs to attain. The power source might indeed be a 1.5V battery but this tells us nothing about what circuitry is attached to that battery, certainly it is not directly connected to the flash capacitor. Different story with the 22,000uF cap for the charging circuit which is directly connected to the 12V battery circuit, therefore starts out at approximately 12V.   

   

As for your noise, as Bob suggested, you might want to try to eliminate potential ground loops thus eliminating the means by which the noise is being introduced in the first place rather than by trying to lower it’s affect after it’s been introduced. Depending on the integrity of the various connections in the audio/radio/antenna circuit then the antenna ground could possibly be part of a ground loop. We are assuming that the co-ax connector for that antenna is wired correctly and that you’re not depending on the local ground to be part of the antenna circuit, only the attachment to the ground plane???????????  

   

Bob McC  

           

  

From: owner-aeroelectric-list-server(at)matronics.com [mailto:owner-aeroelectric-list-server(at)matronics.com] On Behalf Of Dan Billingsley

 Sent: Sunday, April 15, 2012 3:46 PM

 To: aeroelectric-list(at)matronics.com

 Subject: Re: Re: Looking for suggestions  

  

       

   

     	  Quote: 	
		    

             

  

From: user9253 <fran4sew(at)banyanol.com>

 To: aeroelectric-list(at)matronics.com 

 Sent: Sunday, April 15, 2012 8:45 AM

 Subject: Re: Looking for suggestions  

  



 --> AeroElectric-List message posted by: "user9253" <fran4sew(at)banyanol.com (fran4sew(at)banyanol.com)>

 

 Dan,

 A resistor is not necessary as the lamp provides a load.  

    

Yeah, I was just thinking of getting around not using the lamp and getting a digital reading of the discharging cap.

 The voltage of a capacitor can never be more than the voltage that was used  to charge it up.  

    

..I am always willing to be corrected and learned...but I must disagree that if a 22,000mF is filled up, then when discharged there will be a much higher initial voltage reading than let's say the 12 V battery that charged it. Example: if you take one of the disposable cameras that use a flash and run a positive and negative lead off of that electrolytic cap...hook it up to a volt meter and press the button, I have gotten between 300 and 400 volts each time. Most of these cameras use a AA (or 1.5V cell).

   According to Ken and Bob's posts above, a capacitor is not very effective at alleviating noise. Agreed...so I might want to look at a choke?

   Are the headset jacks electrically isolated from the aircraft frame with insulating washers? Yes, the jacks were the first thing I checked when I was introduced to my system whine. Could that frame-grounded antenna in the back be a factor?  

    

   

    

Thanks for all the assistance. And someone set me straight if I am off base about the caps holding high voltages.  

    

Dan 

 Joe

 

 --------

 Joe Gores

 

 

 

 

 Read this topic online here:

 

 http://forums.matronics.com/viewtopic.php?p=370863#370863<;         - The AeroElectric-List Email Forum -

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_________________
Bob McC
Falco #908
(just starting)

nuckolls.bob(at)aeroelect
Guest

Posted: Sun Apr 15, 2012 1:13 pm Post subject: Looking for suggestions

This has the look and smell of a ground-loop issue.

A few years back, I looked at the relative effectiveness

of filtering the ripple component off a the B&C SD-8 alternator.

One captured trace can be seen here:



    I was surprised that I had not posted the constellation

    of plots that explored numerous operating conditions

    relating to SD-8 noise plots. I found the data I

    recalled, posted it to aeroelectric.com and re-organized

    the data plots folder on the website. Here's the SD-8

    stuff in total.



http://tinyurl.com/7yr9h4p

   Bob . . .

user9253

Joined: 28 Mar 2008
Posts: 1938
Location: Riley TWP Michigan

Posted: Sun Apr 15, 2012 1:23 pm Post subject: Re: Looking for suggestions

 	  Quote: 	
		  someone set me straight if I am off base about the caps holding high voltages 	


The high voltage that charges a capacitor in a camera flash does not come directly from the battery.  Pulsing battery current  is applied to the primary of a transformer.  High voltage from the transformer secondary is what charges the capacitor.

  If a 22,000ÂµF capacitor is charged on the workbench, the capacitor will never have a higher voltage than whatever was applied to it.

  Below are a couple of links to camera flash circuits.

Joe

http://www.repairfaq.org/sam/kflashm.gif



http://www.increa.com/reverse/dc/

_________________
Joe Gores

user9253

Joined: 28 Mar 2008
Posts: 1938
Location: Riley TWP Michigan

Posted: Sun Apr 15, 2012 2:12 pm Post subject: Re: Looking for suggestions

 	  Quote: 	
		  Sorry Joe, but what you're seeing with the disposable flash camera capacitor is the result of the charging circuit. 	




Charlie,

  It was Dan who measured the flash camera capacitor voltage, not me.  Dan had mixed his reply in with a quote from my previous post.  That made it confusing as to who wrote what.

  I think that most of us agree that a capacitor will never hold more than what was put into it.

  Thanks for the link to How Stuff Works.

Joe



Do NOT archive

_________________
Joe Gores

dan(at)azshowersolutions.
Guest

Posted: Sun Apr 15, 2012 5:08 pm Post subject: Looking for suggestions

Joe, Apologies in order and I once again stand corrected. Dang little electrons...just when I think I'm getting a grasp on em they change directions. I certainly learned something here and enjoyed looking at the camera flash schematic...makes sense now. 

Dan

 	  Quote: 	
		           From: user9253 <fran4sew(at)banyanol.com>

 To: aeroelectric-list(at)matronics.com 

 Sent: Sunday, April 15, 2012 2:23 PM

 Subject: Re: Looking for suggestions

 --> AeroElectric-List message posted by: "user9253" <fran4sew(at)banyanol.com (fran4sew(at)banyanol.com)>

 	  Quote: 	
		   someone set me straight if I am off base about the caps holding high voltages

The high voltage that charges a capacitor in a camera flash does not come directly from the battery.  Pulsing battery current  is applied to the primary of a transformer.  High voltage from the transformer secondary is what charges the capacitor.

  If a 22,000ÂµF capacitor is charged on the workbench, the capacitor will never have a higher voltage than whatever was applied to it.

  Below are a couple of links to camera flash circuits.

Joe

http://www.repairfaq.org/sam/kflashm.gif

http://www.increa.com/reverse/dc/

--------

Joe Gores

Read this topic online  here:

http://forums.matronics.com/viewtopic.php?p=370892#370892http://www.matronics.com/Navigator?               - MATRONICS WEB FORUMS -<                    &nbsp========================

 [quote][b]

dan(at)azshowersolutions.
Guest

Posted: Sun Apr 15, 2012 5:14 pm Post subject: Looking for suggestions

From: Bob McCallum <robert.mccallum2(at)sympatico.ca>

To: aeroelectric-list(at)matronics.com

Sent: Sun, April 15, 2012 2:14:09 PM

Subject: RE: AeroElectric-List: Re: Looking for suggestions

Dan;   

There is no way for a capacitor to attain a voltage higher than that which was used to charge it. The camera is a bad example because it more closely resembles your strobes whose capacitor might indeed be several hundred volts, but it is not charged by directly applying battery voltage. There is electronic circuitry involved which can theoretically apply any voltage which the designer of the circuit decides he needs to attain. The power source might indeed be a 1.5V battery but this tells us nothing about what circuitry is attached to that battery, certainly it is not directly connected to the flash capacitor. Different story with the 22,000uF cap for the charging circuit which is directly connected to the 12V battery circuit, therefore starts out at approximately 12V. Now understood   

As for your noise, as Bob suggested, you might want to try to eliminate potential ground loops thus eliminating the means by which the noise is being introduced in the first place rather than by trying to lower itâ€™s affect after itâ€™s been introduced. Depending on the integrity of the various connections in the audio/radio/antenna circuit then the antenna ground could possibly be part of a ground loop. We are assuming that the co-ax connector for that antenna is wired correctly and that youâ€™re not depending on the local ground to be part of the antenna circuit, only the attachment to the ground plane??????????? Well, you might be on to something here. The ground of the coax (outer wire) WAS connected to my air-frame (tube & fabric plane) to operate AS the ground plane. This was done on my buddies Kitfox and has operated without a hitch for 8 years. He is very readable and transmits with no issue. As a Ham radio operator I am very aware of how a ground plane should be installed and I would have made one if I had the room under the antenna          (I don't)  As mentioned in an earlier post, my com antenna is built into the vertical stab (again how a friend has his).  The differences between the two planes IS how the electrical systems are installed. I went with Z-16 and all grounds going to a bus (but not the antenna). The tower says my transmissions are clear and  the reception is good as well, but it sure is sounding like I created a ground loop. Guess I will need to figure out what to do with the antenna.

Thanks Bob & Bob,

Dan   

Bob McC   

From: owner-aeroelectric-list-server(at)matronics.com [mailto:owner-aeroelectric-list-server(at)matronics.com] On Behalf Of Dan Billingsley

 Sent: Sunday, April 15, 2012 3:46 PM

 To: aeroelectric-list(at)matronics.com

 Subject: Re: Re: Looking for suggestions   

     	  Quote: 	

From: user9253 <fran4sew(at)banyanol.com>

 To: aeroelectric-list(at)matronics.com 

 Sent: Sunday, April 15, 2012 8:45 AM

 Subject: Re: Looking for suggestions   

 --> AeroElectric-List message posted by: "user9253" <fran4sew(at)banyanol.com (fran4sew(at)banyanol.com)>

 Dan,

 A resistor is not necessary as the lamp provides a load.   

Yeah, I was just thinking of getting around not using the lamp and getting a digital reading of the discharging cap.

 The voltage of a capacitor can never be more than the voltage that was used  to charge it up.   

..I am always willing to be corrected and learned...but I must disagree that if a 22,000mF is filled up, then when discharged there will be a much higher initial voltage reading than let's say the 12 V battery that charged it. Example: if you take one of the disposable cameras that use a flash and run a positive and negative lead off of that electrolytic cap...hook it up to a volt meter and press the button, I have gotten between 300 and 400 volts each time. Most of these cameras use a AA (or 1.5V cell).

   According to Ken and Bob's posts above, a capacitor is not very effective at alleviating noise. Agreed...so I might want to look at a choke?

   Are the headset jacks electrically isolated from the aircraft frame with insulating washers? Yes, the jacks were the first thing I checked when I was introduced to my system whine. Could that frame-grounded antenna in the back be a factor?   

Thanks for all the assistance. And someone set me straight if I am off base about the caps holding high voltages.   

Dan 

 Joe

 --------

 Joe Gores

 Read this topic online here:

 http://forums.matronics.com/viewtopic.php?p=370863#370863<;         - The AeroElectric-List Email Forum -

 http://www.matronics.com/Navigator?AeroElectric-List

 FORUMo available via the Web Forums!

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

      http://www.matronics.com/Navigator?AeroElectric-Listhttp://forums.matronics.com  	
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 [quote][b]

nuckolls.bob(at)aeroelect
Guest

Posted: Sun Apr 15, 2012 7:00 pm Post subject: Looking for suggestions

 	  Quote: 	
		            (I don't)  As mentioned in an earlier post, my com antenna is built into the vertical stab (again how a friend has his).  The differences between the two planes IS how the electrical systems are installed. I went with Z-16 and all grounds going to a bus (but not the antenna). The tower says my transmissions are clear and the reception is good as well, but it sure is sounding like I created a ground loop. Guess I will need to figure out what to do with the antenna. 	


   I really doubt that the coax ground

   to the airframe is the culprit here . . .

   unless for some strange, as yet undiscovered

   reason it is the ONLY ground for that radio

   or cluster of black boxes.



   Do all of your box-grounds go to the

   common power bus and all shield and

   signal grounds connect to their respective

   LO or GND pins on the boxes?



 

   Bob . . .    [quote][b]

user9253

Joined: 28 Mar 2008
Posts: 1938
Location: Riley TWP Michigan

Posted: Sun Apr 15, 2012 8:52 pm Post subject: Re: Looking for suggestions

I am trying to understand why a ground loop causes problems with audio noise.  To me, a ground loop means that the negative side of the electrical system is connected to ground at two or more points.  Current has two possible parallel paths: either through the negative wire or through the airframe.  If any voltage is dropped between the two points where the negative wire is grounded, then the current going to one load will affect the voltage and thus the current gong to the other load.

  It would seem that a similar effect could occur on the positive side of the circuit.  If the current of two or more loads shares the same conductor, then varying-current going to one load could affect the current going to another load.

  In Dan's airplane, maybe the voltage dropped across the E-Bus diode is causing the dynamo whine in the audio system.  It would be interesting to know if shorting out that diode eliminates the noise. Another experiment to try would be to shut off unneeded loads on the E-Bus to see if reducing total current will reduce the noise.

  The ideal electrical system would be grounded at only one point; thus no current whatsoever would flow through the airframe.  That is difficult to accomplish since avionics are internally grounded to their cases.

  Even if each load had discrete conductors, they all must eventually merge at the source (alternator or dynamo).  Why doesn't the current of one load affect the current of another load, since they are combined at the source?

  Bob, do you have any words of wisdom to explain the physics involved?

Joe

_________________
Joe Gores

dan(at)azshowersolutions.
Guest

Posted: Mon Apr 16, 2012 5:59 am Post subject: Looking for suggestions

[quote]        





   I really doubt that the coax ground

   to the airframe is the culprit here . . .

   unless for some strange, as yet undiscovered

   reason it is the ONLY ground for that radio

   or cluster of black boxes.



   Do all of your box-grounds go to the

   common power bus  If you were asking do all the box-grounds go to a common ground bus? Yes I have a ground bus on the firewall that passes through to engine compartment. ALL grounds for anything electrical on either side of the firewall was sent to this ground bus. Even sent a braided wire to the engine block.

and all shield and

   signal grounds connect to their respective

   LO or GND pins on the boxes? This I will need to check again, but my initial answer is I'm fairly certain. The other thing I have discovered in my system yesterday...I went to the airport in the morning only to find the new battery dead. I charged it and came back later in the day and it was good to go. I checked both buses with everything off and found the Master bus was showing 24mV being pulled. The E-bus was 0 volts. Didn't have time to trace the culprit load.

Dan

     Bob . . .    

 	  Quote: 	
		  http://www.matron======


	




 

 

 [b]

nuckolls.bob(at)aeroelect
Guest

Posted: Mon Apr 16, 2012 8:14 am Post subject: Looking for suggestions

At 11:52 PM 4/15/2012, you wrote:




I am trying to understand why a ground loop causes problems with 

audio noise.  To me, a ground loop means that the negative side of 

the electrical system is connected to ground at two or more 

points.  Current has two possible parallel paths: either through the 

negative wire or through the airframe.  If any voltage is dropped 

between the two points where the negative wire is grounded, then the 

current going to one load will affect the voltage and thus the 

current gong to the other load.



    Close. This isn't about dual paths in the same system,

    it's about SHARED paths in two systems where a strong

    antagonist (alternator, strobe, motor) induces noisy

    current into a path SHARED by a potential victim (audio

    system, small signal instrumentation, etc).



The ideal electrical system would be grounded at only one point; thus 

no current whatsoever would flow through the airframe.  That is 

difficult to accomplish since avionics are internally grounded to their cases.



    Yes. The design goal is to insure that ALL

    potential victims in a constellation of

    appliances have no shared ground paths with

    potential antagonists.



    Example: Grounding the headsets and/or microphones

    locally causes tiny audio signals to be carried on

    an airframe path shared with currents flowing into

    or out of alternators, etc.



    This is why the avionics ground was crafted.



http://tinyurl.com/7hvmat6



    The idea is to CLUSTER all grounds for potential

    victims together on the panel before taking a

    jumper to power ground on the airframe or at the

    fire wall.



    General rules for avoiding ground loops is

    illustrated in the Z-figures:



http://tinyurl.com/6m3bk8k



http://tinyurl.com/7fnbhqn



http://tinyurl.com/6w87rvb

   Bob . . .

nuckolls.bob(at)aeroelect
Guest

Posted: Mon Apr 16, 2012 8:19 am Post subject: Looking for suggestions

The other thing I have discovered in my system yesterday...I went to 

the airport in the morning only to find the new battery dead. I 

charged it and came back later in the day and it was good to go. I 

checked both buses with everything off and found the Master bus was 

showing 24mV being pulled. The E-bus was 0 volts. Didn't have time to 

trace the culprit load.

    Not sure that a tiny voltage on the bus is significant.

    With everything turned OFF, disconnect a battery lead and

    put your multimeter in SERIES with that battery lead and

    measure CURRENT. If you have a battery bus, there may

    be some device like a clock or a device needing memory

    support voltage connected to it. A few milliamps of

    constant drain is not a big deal . . . as long as you

    KNOW and AGREE to the use of that energy. But for most

    airplanes, this current will for all practical purposes

    be ZERO.



    Refresh my memory: What's your radio/audio system

    look like?

   Bob . . .

dan(at)azshowersolutions.
Guest

Posted: Mon Apr 16, 2012 6:26 pm Post subject: Looking for suggestions

 	  Quote: 	
		          

The other thing I have discovered in my system yesterday...I went to the airport in the morning only to find the new battery dead. I charged it and came back later in the day and it was good to go. I checked both buses with everything off and found the Master bus was showing 24mV being pulled. The E-bus was 0  volts. Didn't have time to trace the culprit load.

   Not sure that a tiny voltage on the bus is significant.

   With everything turned OFF, disconnect a battery lead and

   put your multimeter in SERIES with that battery lead and

   measure CURRENT. If you have a battery bus, there may

   be some device like a clock or a device needing memory

   support voltage connected to it. A few milliamps of

   constant drain is not a big deal . . . as long as you

   KNOW and AGREE to the use of that energy. But for most

   airplanes, this current will for all practical purposes

   be ZERO.



   Refresh my memory: What's your radio/audio system

   look like?

PM1000

Garmin SL-40

I also took a shortcut doing pinouts between avionics with a commercial junction box made by  http://www.approachfaststack.com/hubs.html  I used the Pro-X.

It was quite a time saver, they have good reviews and they were quite thorough. If interested I have a connection schematic from them.

Dan 



  Bob . . .

user9253

Joined: 28 Mar 2008
Posts: 1938
Location: Riley TWP Michigan

Posted: Mon Apr 16, 2012 8:08 pm Post subject: Re: Looking for suggestions

Bob,

Since noise can be caused by two or more circuits sharing the same conductor, would it help to use a larger conductor?  Have any experiments been done comparing noise with various wire sizes?

Joe

_________________
Joe Gores

henador_titzoff(at)yahoo.
Guest

Posted: Tue Apr 17, 2012 4:03 am Post subject: Looking for suggestions

Joe,

A larger conductor would help only if the noise you perceive is causing problems is actually an offset voltage caused by current times resistance in the wire.  In other words, current pulled by one load can cause an offset voltage for the second load, and the second load can't handle the offset.

But noise is AC with a spectrum content up there at high frequencies.  So when you say "noise," let's assume it is high frequency noise. If this is true, increasing conductor size only helps if it decreases its impedance, which is unlikely.  You're better off rewiring such that each load has its own dedicated ground and power wires.

 

Henador Titzoff



         From: user9253 <fran4sew(at)banyanol.com>

 To: aeroelectric-list(at)matronics.com 

 Sent: Tuesday, April 17, 2012 12:08 AM

 Subject: AeroElectric-List: Re: Looking for suggestions

  

 

--> AeroElectric-List message posted by: "user9253" <fran4sew(at)banyanol.com (fran4sew(at)banyanol.com)>



Bob,

Since noise can be caused by two or more circuits sharing the same conductor, would it help to use a larger conductor?  Have any experiments  been done comparing noise with various wire sizes?

Joe



--------

Joe Gores





Read this topic online here:



http://forums.matronics.com/viewtopic.php?p=371015#371015

AeroElectric-List" target="_blank">http://www.matronics.com/Navigator?Aersp;           nbsp;                 -Matt Dralle,tribution" target="_blank">http://www.matronics.com/contribution

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 [quote][b]

nuckolls.bob(at)aeroelect
Guest

Posted: Tue Apr 17, 2012 6:31 pm Post subject: Looking for suggestions

At 09:24 PM 4/16/2012, you wrote:



  We need to do some experiments to see where the noise

  is getting into the system.



  When you CAN hear the noise, is it affected by the

  volume control on the radio?



  Does your transmitter have a side-tone feature,

  in other words, can you hear yourself in the

  headphones when you talk on the transmitter?



  Does the noise go away when you transmit?



  If I recall correctly, the noise does go away

  when you close the alternate feed switch to

  the e-bus.



  Just for grins, lets try bypassing the normal

  feed diode. In other words, leave the alternate

  feed switch open and short around the normal

  feed diode.



   Bob . . .

dan(at)azshowersolutions.
Guest

Posted: Tue Apr 17, 2012 9:04 pm Post subject: Looking for suggestions

ok will try these things after work tomorrow. Thanks, Dan



[quote]        From: "Robert L. Nuckolls, III" <nuckolls.bob(at)aeroelectric.com>

 To: aeroelectric-list(at)matronics.com 

 Sent: Tuesday, April 17, 2012 7:29 PM

 Subject: Re: Re: Looking for  suggestions

  

 

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



At 09:24 PM 4/16/2012, you wrote:



 We need to do some experiments to see where the noise

 is getting into the system.



 When you CAN hear the noise, is it affected by the

 volume control on the radio?



 Does your transmitter have a side-tone feature,

 in other words, can you hear yourself in the

 headphones when you talk on the transmitter?



 Does the noise go away when you transmit?



 If I recall correctly, the noise does go away

 when you close the alternate feed switch to

 the e-bus.



 Just for grins, lets try bypassing the normal

 feed diode. In other words, leave the alternate

 feed switch open and short around the normal

 feed diode.



  Bob . . . p;  --> http://www.matronics.com/Navigator?AeroElectric-List========================

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