X-Virus-Scanned: clean according to Sophos on Logan.com X-SpamCatcher-Score: 2 [X] Return-Path: Sender: To: lml@lancaironline.net Date: Fri, 06 Apr 2007 21:28:52 -0400 Message-ID: X-Original-Return-Path: Received: from vms046pub.verizon.net ([206.46.252.46] verified) by logan.com (CommuniGate Pro SMTP 5.1.8) with ESMTP id 1969959 for lml@lancaironline.net; Thu, 05 Apr 2007 23:27:28 -0400 Received: from jacky0da39824a ([71.111.169.130]) by vms046.mailsrvcs.net (Sun Java System Messaging Server 6.2-6.01 (built Apr 3 2006)) with ESMTPA id <0JG2006EJ48ZN5JA@vms046.mailsrvcs.net> for lml@lancaironline.net; Thu, 05 Apr 2007 22:27:03 -0500 (CDT) X-Original-Date: Thu, 05 Apr 2007 20:26:47 -0700 From: "Tom Gourley" Subject: Re: [LML] Ground connection X-Original-To: "Lancair Mailing List" Reply-to: "Tom Gourley" X-Original-Message-id: <001801c777fb$68f43540$650610ac@jacky0da39824a> MIME-version: 1.0 X-MIMEOLE: Produced By Microsoft MimeOLE V6.00.2900.3028 X-Mailer: Microsoft Outlook Express 6.00.2900.3028 Content-type: multipart/alternative; boundary="----=_NextPart_000_0015_01C777C0.BBCD2B40" X-Priority: 3 X-MSMail-priority: Normal References: This is a multi-part message in MIME format. ------=_NextPart_000_0015_01C777C0.BBCD2B40 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable In order to tidy up the spag, and perhaps improve the radio performance, = I wondered if I was to organise the ground points and have the = electrical services grounded to a common point and the avionics to a = separate common point. Dom, What you want to avoid is multiple grounding points that are = interconnected through multiple paths. I would recommend a single heavy = duty ground point on the firewall that the large cable from the negative = battery terminal attaches to. The battery negative lead should be at = least #4 cable as it will carry the current from the starter back to the = battery. Typically the ground point on the firewall is a stud that goes = through the firewall to provide a grounding point for things under the = cowl, like the starter. Unless the manufacturer recommends otherwise I = would not ground engine sensors (fuel flow, fuel pressure, oil pressure) = to this point. I would route them with the other wires from the sensors = to the engine interface box. =20 Behind the panel I would run the ground wires from the avionics, and = whatever else is currently grounded behind the panel, to a single ground = bus. You can buy grounding busses or make one from a bar of copper or = brass. I would then run a single heavy wire, #10 or #8, from that = ground bus to the ground stud on the firewall. (You could run it all = the way to battery instead but that's probably overkill.) If you have = more than one grounding bus run a heavy wire from each bus to the common = ground point. Don't daisy-chain grounding points. When you're done = there should be a single wire from each grounding bus, if you have more = than one, to the common ground point and no wires running between = grounding busses. =20 For audio wiring follow the audio panel manufacturer's instructions. = Typically this involves using a shielded multiconductor cable from each = audio source, or destination, to a channel on the audio panel. Most = manufacturers then recommend grounding the shield at the audio panel = only. Again, follow the manufacturer's instructions on how to terminate = the shields. If this requires soldering wires to the shield that are = then tied to the connector backshell or the audio panel chassis, keep = these wires as short as possible. Never use the cable shield as a = return. For example a standared stereo headset jack will have a wire = for left audio, one for right audio, and one for return. In this case = you would use 3-conductor cable. Do not use 2-conductor and then cheat = and use the shield for a return. If I've made an error in my descriptions I'm sure someone will bring it = to my attention. Tom Gourley ------=_NextPart_000_0015_01C777C0.BBCD2B40 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable

In order to tidy up = the spag,=20 and perhaps improve the radio performance, I wondered if I was to = organise the=20 ground points and have the electrical services grounded to a common = point and=20 the avionics to a separate common = point.

 
Dom,
 
What you want to avoid is multiple = grounding points=20 that are interconnected through multiple paths.  I would recommend = a single=20 heavy duty ground point on the firewall that the large cable from the = negative=20 battery terminal attaches to.  The battery negative = lead should be at=20 least #4 cable as it will carry the current from the starter back to the = battery.  Typically the ground point on the firewall is a = stud=20 that goes through the firewall to provide a grounding point for things = under the=20 cowl, like the starter.  Unless the manufacturer recommends = otherwise I=20 would not ground engine sensors (fuel flow, fuel pressure, oil pressure) = to this=20 point.  I would route them with the other wires from the sensors to = the=20 engine interface box. 
 
Behind the panel I would run the ground = wires from the avionics, and whatever else is currently=20 grounded behind the panel, to a single ground bus.  You can = buy=20 grounding busses or make one from a bar of copper or brass.  I = would then=20 run a single heavy wire, #10 or #8, from that ground bus to the ground = stud on=20 the firewall.  (You could run it all the way to battery instead but = that's=20 probably overkill.)  If you have more than one grounding bus run a = heavy=20 wire from each bus to the common ground point.  Don't daisy-chain = grounding=20 points.  When you're done there should be a single wire from each = grounding=20 bus, if you have more than one, to the common ground point and no wires = running=20 between grounding busses. 
 
For audio wiring follow the audio panel = manufacturer's instructions.  Typically this involves using = a shielded=20 multiconductor cable from each audio source, or destination, to a = channel=20 on the audio panel.  Most manufacturers then recommend grounding = the shield=20 at the audio panel only.  Again, follow the manufacturer's = instructions on=20 how to terminate the shields.  If this requires soldering wires to = the=20 shield that are then tied to the connector backshell or the audio panel = chassis,=20 keep these wires as short as possible.  Never use the cable shield = as a=20 return.  For example a standared stereo headset jack will have a = wire for=20 left audio, one for right audio, and one for return.  In this case = you=20 would use 3-conductor cable.  Do not use 2-conductor and then cheat = and use=20 the shield for a return.
 
If I've made an error in my = descriptions I'm sure=20 someone will bring it to my attention.
 
Tom Gourley
 
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