Electric Shielding? - Ducati.ms

AXE · Dec 20th, 2009, 11:42 am

I have a question about static elctricity for all you electric experts.

I am running a Passport 8500 radar detector that I have hardwired into the bike near the battery. I have the wire running to the handlebars following the bikes wiring harness along the left side of the tank. This wire is basically a telephone cord type wire. I also run a MixIt 2 amp/splitter so I can run my radar detector and Sirius Stilletto radio/mp3 player. I listen to them using some custom molded earplugs with speakers built in them.

The problem I have is I get a very faint hum or growl coming through the headphones when riding. It seems to amplify a bit when the motor is wrapped up, but barely discernably higher. I don't seem to notice it unless I am connected either directly or through the amp to the detector. Therefore, I believe it is coming from the power supply wire leading into the detector. I'd never seen this problem with my FZ1 with the same setup, so I think it is unique to the electrical system on the Hyper or where I have the wires run.

I am wondering if adding some type of shielding to the power supply wire will kill the static noise or not. I have seen some mesh type sleeving or wrap that can be added or I have also seen that you can simply run another wire along it and ground it to the bike. What do you think will work best to prevent this static noise?

Thanks.

Out!

dave2riff · Dec 20th, 2009, 1:03 pm

It is true that where you run the wires matters as far as picking up interference.
On this bike the source of the EMI is the high voltage to the plugs and also
the current pulses driving the fuel injectors, so you will likely hear the pitch of
the interference vary with RPM. Routing supply wires away from the ignition
and fuel injector harnesses is a good idea.

Shielding wires can be tricky for a number of reasons, and how you ground the
shield can make a big difference. I've seen guys have troubles with bare braided
shielding on +12V wires, leading to shorting and fires in car stereo apps. Better
to use a pre-made shielded two-wire cable that has PVC insulation on the
outside (over the metal shield braid).

Two suggestions: Make sure you have a solid ground return on this setup. Does
the problem go away if you bypass the MixIt splitter? I get the feeling there
is some sort of grounding problem with that device.
Also, as an alternative to shielding, you could use an inline filter on +12V supply,
close as possible to the Sirius device. Unfortunately, these involve splicing
into the supply wire. Car stereo shops sell inline power filters. A capacitor
from +12V to ground in the splitter should also help filter noise (try 50uF/25V).

Another thought-- ground loops. If either the radar detector or the Sirius device has
it's case grounded, and there is another ground wire going back into the splitter,
this can form a "ground loop" and cause susceptability to EMI. Worth a look.

jcm3 · Dec 20th, 2009, 1:33 pm

Its definately a ground loop. There is a difference in the ground potential between the radar detector ground and the MixIt amp's ground. You also have a ground shared by the two on the headphone connector. A ground loop isolator on either audio connection, or grounding both devices to the same point should eliminate the problem.

I've linked a decent isolator from Crutchfield.

http://www.crutchfield.com/S-BdDBGUD...se-Filter.html

jcmitch

AXE · Dec 21st, 2009, 3:42 pm

Great information. For clarification, both the Sirius radio and the MixIt 2 are running off their own battery sources and are not hard wired or connected to a power source, but rather by a cord from each connecting the detector and headphones. I am not sure if this changes any of your analysis or not.

I was thinking about adding some of this stuff for an easy fix? What do you think?

http://www.custom-shielding.com/sedc...ustommesh.html

or this

http://www.custom-shielding.com/sedc...bleshield.html

Thanks.

Out!

doon · Dec 21st, 2009, 8:02 pm

Quote:

Originally Posted by AXE

I have a question about static elctricity for all you electric experts.

I am running a Passport 8500 radar detector that I have hardwired into the bike near the battery. I have the wire running to the handlebars following the bikes wiring harness along the left side of the tank. This wire is basically a telephone cord type wire. I also run a MixIt 2 amp/splitter so I can run my radar detector and Sirius Stilletto radio/mp3 player. I listen to them using some custom molded earplugs with speakers built in them.

The problem I have is I get a very faint hum or growl coming through the headphones when riding. It seems to amplify a bit when the motor is wrapped up, but barely discernably higher. I don't seem to notice it unless I am connected either directly or through the amp to the detector. Therefore, I believe it is coming from the power supply wire leading into the detector. I'd never seen this problem with my FZ1 with the same setup, so I think it is unique to the electrical system on the Hyper or where I have the wires run.

I am wondering if adding some type of shielding to the power supply wire will kill the static noise or not. I have seen some mesh type sleeving or wrap that can be added or I have also seen that you can simply run another wire along it and ground it to the bike. What do you think will work best to prevent this static noise?

Thanks.

Out!

All the info so far from other people is correct.
It is common practice to use a shielded cable,but you only ground the shield at one end.
Normally the source.
The other end is left open.ie not conected to anything else.
If you do it will not work!!!!

Also as stated bonding all electronics off the shielded cable will/should eliminate electrical noise.

reitsmjo · Dec 28th, 2009, 8:09 am

Quote:

Originally Posted by doon

All the info so far from other people is correct.
It is common practice to use a shielded cable,but you only ground the shield at one end.
Normally the source.
The other end is left open.ie not conected to anything else.
If you do it will not work!!!!

Also as stated bonding all electronics off the shielded cable will/should eliminate electrical noise.

I am curious, does this mean that you need to prevent the shield from touching anything on the frame?

AXE · Dec 28th, 2009, 10:50 am

That is not really the problem as the wire is coated, but it wouldn't hurt to add a protective sleeve to ensure it wouldn't wear through. I think the problem is just inherent electrical interference from the bike electronics with the wire leading to the detector. This creates a small amount of static or distorted bass type noise.

Out!