Matronics Email Lists :: View topic

Matronics Email Lists
Web Forum Interface to the Matronics Email Lists

Get Email Distribution Too! FAQ Search Memberlist Usergroups Register

Profile Log in to check your private messages Log in

Cross talk problem

Matronics Email Lists Forum Index -> AeroElectric-List

View previous topic :: View next topic

Author Message

jonlaury

Joined: 06 Nov 2006
Posts: 336

Posted: Mon Feb 06, 2012 10:47 am Post subject: Cross talk problem

Listers.

I have installed an EyeBeam mini in my composite airframe. Unfortunately I do not have a schematic of the unit, but it uses capacitance (touch) to control the on/off function and dimming.



 The shielded, twisted pair power and ground wire cable parallel unshielded, untwisted wires to the 4 ohm 1.25" x 1.75" cabin speaker for a distance of about 5' . At that point the cabin speaker pair becomes a  twisted and shielded cable. The two cables parallel each other for an additional 12'. The shield for the speaker is grounded at the audio panel and the shield for the EB is grounded at the ship's single point ground bus.



The problem:

When I key the microphone, the EB turns on. If I key it again, the EB begins flashing uncontrollably. It is unresponsive to the dimming control and the on/off switch. The only way to stop the flashing is to disconnect the EB from power.  The EB works as intended when connected to battery power independent of the ship's electrical system.



Attempts at a solution:

Thinking that the the magnetic field of the speaker magnet may be causing the problem, the speaker was disconnected and the mic was keyed. The EB exhibited the same uncontrollable flashing upon keying the microphone.



Any ideas on what's happening and/or how to fix it?



Thanks,

John

- The Matronics AeroElectric-List Email Forum -

Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

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

enginerdy(at)gmail.com
Guest

Posted: Mon Feb 06, 2012 12:12 pm Post subject: Cross talk problem

Try keying the mic without the comm radio on. Chances are it's RF interference. If that's the case, get a clamp-on ferrite kit and start experimenting.



Touch technology can be very sensitive to RF interference, and that could be leaking into the power lines from a number of places. For a start, I would recommend putting a ferrite right at the power input to the light. Another reasonable place to try is on the speaker line, where it meets the lighting power.



These are made to go around a set of wires (power and ground, power ground and serial comm) so you should only need one for a given set of wires. ie one for the speaker wires, one for the EB power lines. They're pretty cheap, so you can easily pick a few to try out.



To pick some appropriate ones:

Digikey.com

search "ferrite"

Under "Filters" pick "Ferrite Cores and Cables for Wiring (469 Items)

Under "Filter Type" pick "Round Cable, Snap On"

Check the "In Stock" box

Press "Apply Filters"



Pick some with reasonable outer diameters (OD) and inner diameters (ID) that will fit around your wiring. There are a lot of variables in ferrite selection still, but in general when choosing between them, higher impedance is better for you.



--Daniel



On Feb 6, 2012, at 12:47 PM, jonlaury wrote:



 	  Quote: 	
		   

 

 Listers.

 I have installed an EyeBeam mini in my composite airframe. Unfortunately I do not have a schematic of the unit, but it uses capacitance (touch) to control the on/off function and dimming.

 

 The shielded, twisted pair power and ground wire cable parallel unshielded, untwisted wires to the 4 ohm 1.25" x 1.75" cabin speaker for a distance of about 5' . At that point the cabin speaker pair becomes a  twisted and shielded cable. The two cables parallel each other for an additional 12'. The shield for the speaker is grounded at the audio panel and the shield for the EB is grounded at the ship's single point ground bus.

 

 The problem:

 When I key the microphone, the EB turns on. If I key it again, the EB begins flashing uncontrollably. It is unresponsive to the dimming control and the on/off switch. The only way to stop the flashing is to disconnect the EB from power.  The EB works as intended when connected to battery power independent of the ship's electrical system.

 

 Attempts at a solution:

 Thinking that the the magnetic field of the speaker magnet may be causing the problem, the speaker was disconnected and the mic was keyed. The EB exhibited the same uncontrollable flashing upon keying the microphone.

 

 Any ideas on what's happening and/or how to fix it?

 

 Thanks,

 John

 

 

 

 

 Read this topic online here:

 

 http://forums.matronics.com/viewtopic.php?p=365744#365744

- The Matronics AeroElectric-List Email Forum -

Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

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

jonlaury

Joined: 06 Nov 2006
Posts: 336

Posted: Tue Feb 07, 2012 8:54 am Post subject: Re: Cross talk problem

Daniel,

Thanks for that. I'll give it a try.



 	  Quote: 	
		  Another reasonable place to try is on the speaker line, where it meets the lighting power. 	




Do you mean where the two sets of wires come together from their respective sources of Audio Panel and the power/ground bus's, or from the appliance ends at the speaker and light? Does it matter? The appliance ends are right next to each other in a small overhead console and their wire runs are parallel for about 17', the first 5' of speaker wire being unshielded/untwisted.



Best,

John

- The Matronics AeroElectric-List Email Forum -

Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

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

enginerdy(at)gmail.com
Guest

Posted: Tue Feb 07, 2012 9:41 pm Post subject: Cross talk problem

I meant where the speaker line joins the light power wiring at the panel. If it's RF, it's leaking in from somewhere, and you need to separate that source from the problem area.



Another possibility is clamping the ferrite mid-way down the line, on both lines separately, or just clamping the entire bundle with one larger ferrite.



You are trying to isolate the noise source from the rest of the system (particularly the touch-light). If you have wires bundled together, or running near each other, RF can jump across cables. Ferrites kill the RF, but if, for example, you put just one ferrite on the power, midway down the 17' run, the RF energy will have no problem jumping from one cable to the other freely, bypassing the ferrite filter.



Have you tried the experiment with the comm radio off? The RF theory sounds good, but it's best to rule easy things out if you can, even if it sounds unlikely.

On Feb 7, 2012, at 10:54 AM, jonlaury wrote:



 	  Quote: 	
		   

 

 Daniel,

 Thanks for that. I'll give it a try.

 

 

> Another reasonable place to try is on the speaker line, where it meets the lighting power.

 

 

 Do you mean where the two sets of wires come together from their respective sources of Audio Panel and the power/ground bus's, or from the appliance ends at the speaker and light? Does it matter? The appliance ends are right next to each other in a small overhead console and their wire runs are parallel for about 17', the first 5' of speaker wire being unshielded/untwisted.

 

 Best,

 John

 

 

 

 

 Read this topic online here:

 

 http://forums.matronics.com/viewtopic.php?p=365807#365807

- The Matronics AeroElectric-List Email Forum -

Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

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

jonlaury

Joined: 06 Nov 2006
Posts: 336

Posted: Wed Feb 08, 2012 8:19 am Post subject: Re: Cross talk problem

 	  Quote: 	
		  I meant where the speaker line joins the light power wiring at the panel. 	




OK, I think I get the idea. The two cables are not co-located at the power end (one comes out of  the audio panel, one comes from the battery bus) so I'll try putting a ferrite on the speaker cable at the point of convergence. I gather that this is not an exact science, so I'll try the different locations that you suggest. 

Haven't had a chance to try with  the com radio off. But the problem goes away with the audio panel off, or (IIRC) with the speaker button deselected with the AP on.



Right now I'm focused on getting my W&B done and anything else for my DAR appointment.



Thanks

John

- The Matronics AeroElectric-List Email Forum -

Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

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

Display posts from previous:

	Matronics Email Lists Forum Index -> AeroElectric-List	All times are GMT - 8 Hours
Page 1 of 1

Jump to:

You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
You cannot attach files in this forum
You can download files in this forum