X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Tue, 26 Nov 2013 09:15:44 -0500 Message-ID: X-Original-Return-Path: Received: from qmta14.westchester.pa.mail.comcast.net ([76.96.59.212] verified) by logan.com (CommuniGate Pro SMTP 6.0.7) with ESMTP id 6614800 for lml@lancaironline.net; Tue, 26 Nov 2013 09:00:15 -0500 Received-SPF: pass receiver=logan.com; client-ip=76.96.59.212; envelope-from=jmorgan1023@comcast.net Received: from omta15.westchester.pa.mail.comcast.net ([76.96.62.87]) by qmta14.westchester.pa.mail.comcast.net with comcast id uDkf1m0061swQuc5EDziTl; Tue, 26 Nov 2013 13:59:42 +0000 Received: from [192.168.1.103] ([24.11.157.196]) by omta15.westchester.pa.mail.comcast.net with comcast id uDzi1m00H4EXR5U3bDzitU; Tue, 26 Nov 2013 13:59:42 +0000 From: Jack Morgan Mime-Version: 1.0 (Apple Message framework v1283) Content-Type: multipart/alternative; boundary="Apple-Mail=_533E2F64-3829-498F-BA7E-07B14E302EA3" Subject: Snubbers and electronic gremlins X-Original-Date: Tue, 26 Nov 2013 08:59:42 -0500 In-Reply-To: X-Original-To: Lancair Mailing List References: X-Original-Message-Id: X-Mailer: Apple Mail (2.1283) --Apple-Mail=_533E2F64-3829-498F-BA7E-07B14E302EA3 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=iso-8859-1 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=_533E2F64-3829-498F-BA7E-07B14E302EA3 Content-Transfer-Encoding: quoted-printable Content-Type: text/html; charset=iso-8859-1

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=_533E2F64-3829-498F-BA7E-07B14E302EA3--