X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from elasmtp-banded.atl.sa.earthlink.net ([209.86.89.70] verified) by logan.com (CommuniGate Pro SMTP 6.0.7) with ESMTP id 6614863 for lml@lancaironline.net; Tue, 26 Nov 2013 09:37:43 -0500 Received-SPF: none receiver=logan.com; client-ip=209.86.89.70; envelope-from=colyncase@earthlink.net DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws; s=dk20050327; d=earthlink.net; b=qQL0Iz9MappwGdncIxCpAHyxr4fEfHA6F1zEpfY/I/h0nwRgqX7uLH1OTQzWDrh7; h=Received:From:Mime-Version:Content-Type:Subject:Date:In-Reply-To:To:References:Message-Id:X-Mailer:X-ELNK-Trace:X-Originating-IP; Received: from [70.105.253.253] (helo=[192.168.1.24]) by elasmtp-banded.atl.sa.earthlink.net with esmtpa (Exim 4.67) (envelope-from ) id 1VlJl6-0005wg-Bn for lml@lancaironline.net; Tue, 26 Nov 2013 09:37:00 -0500 From: Colyn Case Mime-Version: 1.0 (Apple Message framework v1085) Content-Type: multipart/alternative; boundary=Apple-Mail-246--852473137 Subject: Re: [LML] A couple Tyco papers on emf reduction in relays Date: Tue, 26 Nov 2013 09:36:59 -0500 In-Reply-To: To: "Lancair Mailing List" References: Message-Id: <328833B9-E27B-4458-9452-5BA458E481D8@earthlink.net> X-Mailer: Apple Mail (2.1085) X-ELNK-Trace: 63d5d3452847f8b1d6dd28457998182d7e972de0d01da940c7b1d71b7f74892936cfa0f0cbc6b6fc350badd9bab72f9c350badd9bab72f9c350badd9bab72f9c X-Originating-IP: 70.105.253.253 --Apple-Mail-246--852473137 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=us-ascii Changing the title back so people who sort on subject will see it. Jack, interesting points about the sneak paths. ...I need some = education about how a snapjack would cause that. I updated the links late last night. I think the content of the articles is still valid. The tyco Kilovac line is NOT an electronic (e.g. solid state ) device. = It's an old fashioned coil style relay. Just a well-done one. I have no objection to mechanical relays. I'm just saying look at the = specs. I'm not sure what model number you are talking about when you say the = pump relay specification is well out of the usage range. What is the = usage range? I think someone published a chart once that showed current = draw vs. starting pressure of that pump. It gets pretty high if the = pressure is high (and it's working). If it starts to have an internal = fault, current will get very high. Then you want to be able to turn it = off. On Nov 26, 2013, at 9:15 AM, Jack Morgan wrote: Hi Colyn, The website has been changed so the links didn't work for me. Please = keep in mind that the mass of the relay makes a difference. The longer = coil current decay caused by a diode snubber is significant in a lighter = weight relay loaded near it's rating as Tyco and others have pointed = out. The heavy solenoid armature used to control the hydraulic pump is = only slightly impacted if at all. The solenoid is also well away from = it's current rating in the pump application. If a diode snubber is used = across the solenoid contacts the whole discussion becomes even more = moot. There have been reports of nose gear collapse in the 320/Legacy style = set up due to sneak paths related to adding various indicator lights = which inadvertently activate the up pump relay. An electronic relay = solution might be more prone to this type issue. I am very conservative = when it comes to electronic relays since they can easily be misapplied = resulting in either failure or sensitivity to other noise sources. Each = manufacturer has their own design so each will have different = sensitivities to noise, etc. I agree that an electronic relay properly = applied is a good solution, but given the variations in the wiring = schematics that seem to creep into our experimental world, they could = also introduce a failure mode. So if a builder goes the electronic route = he/she should be aware that careful testing in all possible voltage, = temperature, radio transmitter, equipment on/off conditions for this = particular aircraft is important. Especially keep in mind that some = FBO's will significantly over voltage 12 volt airplanes with external = power sources which needs to be taken into account if "snap jack" and/or = electronic relay style solutions are implemented. A common specification = for this abuse is twice battery voltage. The "crappy old mechanical solenoid" also has the advantage that 10's of = millions of them have been built over decades which gives them the = benefit of many iterations of quality/manufacturing improvements as = compared to the recent and unique design of each electronic relay. Electronic solutions have the potential to introduce all sorts of head = scratching behavior so each builder should proceed with caution. The = potential reliability improvement may be worth the trip if careful = qualification testing is done in each application. Sorry to be a downer but 50 years of designing electronics into vehicles = has left me scarred........ and amazed. Jack Morgan On Nov 25, 2013, at 10:33 PM, Lancair Mailing List wrote: > From: Colyn Case > Subject: A couple Tyco papers on emf reduction in relays > Date: November 25, 2013 9:06:50 PM EST > To: "lml@lancaironline.net List" >=20 >=20 > I just stumbled across these while researching something else. >=20 > Recently there have been some reference to how to protect switch = circuits connected to relays. Here are two papers done by Tyco which = have been corroborated by certain others and are consistent with Eric = Jones' recommended use of Snapjacks (bi-directional zener diodes). >=20 > Some methods (not recommended here) of protecting the switch contact = result in extending the opening time of the relay, which causes arcing, = bouncing and degeneration of the relay contacts. (not a good thing for = maximizing starter current). >=20 > If you are going to do something in this department, I highly = recommend reading these. (or just use EV100 relays and be done with it) >=20 > http://relays.tycoelectronics.com/appnotes/app_pdfs/13c3311.pdf > =20 > http://relays.tycoelectronics.com/appnotes/app_pdfs/13c3264.pdf >=20 > Colyn >=20 --Apple-Mail-246--852473137 Content-Transfer-Encoding: quoted-printable Content-Type: text/html; charset=us-ascii

The = "crappy old mechanical solenoid" also has the advantage that 10's of = millions of them have been built over decades which gives them the = benefit of many iterations of quality/manufacturing improvements as = compared to the recent and unique design of each electronic = relay.

Electronic solutions have the potential = to introduce all sorts of head scratching behavior so each builder = should proceed with caution. The potential reliability improvement may = be worth the trip if careful qualification testing is done in each = application.

Sorry to be a downer but 50 years = of designing electronics into vehicles has left me scarred........ and = amazed.

Jack Morgan

On = Nov 25, 2013, at 10:33 PM, Lancair Mailing List wrote:

From: Colyn Case <colyncase@earthlink.net>
 A couple Tyco = papers on emf reduction in relays
Date: November 25, 2013 = 9:06:50 PM EST


I just stumbled across these while researching = something else.

Recently there have been some = reference to how to protect switch circuits connected to relays. =  Here are two papers done by Tyco which have been corroborated by = certain others and are consistent with Eric Jones' recommended use of = Snapjacks (bi-directional zener diodes).

Some methods = (not recommended here) of protecting the switch contact result in = extending the opening time of the relay, which causes arcing, bouncing = and degeneration of the relay contacts.  (not a good thing for = maximizing starter current).

If you are going = to do something in this department, I highly recommend reading these. =  (or just use EV100 relays and be done with = it)



= --Apple-Mail-246--852473137--