X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Fri, 19 Apr 2013 13:46:46 -0400 Message-ID: X-Original-Return-Path: Received: from qmta03.westchester.pa.mail.comcast.net ([76.96.62.32] verified) by logan.com (CommuniGate Pro SMTP 6.0.4) with ESMTP id 6210667 for lml@lancaironline.net; Fri, 19 Apr 2013 09:16:03 -0400 Received-SPF: pass receiver=logan.com; client-ip=76.96.62.32; envelope-from=jmorgan1023@comcast.net Received: from omta03.westchester.pa.mail.comcast.net ([76.96.62.27]) by qmta03.westchester.pa.mail.comcast.net with comcast id Rmmr1l00B0bG4ec53pFVtq; Fri, 19 Apr 2013 13:15:29 +0000 Received: from [192.168.1.107] ([68.200.249.129]) by omta03.westchester.pa.mail.comcast.net with comcast id RpF81l00c2oFWjG3PpFDfG; Fri, 19 Apr 2013 13:15:24 +0000 From: Jack Morgan Mime-Version: 1.0 (Apple Message framework v1283) Content-Type: multipart/alternative; boundary="Apple-Mail=_B8A84477-0D7E-4BAA-A427-A3F2EAA9CD94" Subject: Relay snubber X-Original-Date: Fri, 19 Apr 2013 09:15:12 -0400 In-Reply-To: X-Original-To: "Lancair Mailing List" References: X-Original-Message-Id: <0900D305-DF41-401E-AD95-7F721E5E5BEB@comcast.net> X-Mailer: Apple Mail (2.1283) --Apple-Mail=_B8A84477-0D7E-4BAA-A427-A3F2EAA9CD94 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=iso-8859-1 The failed relay is an intermittent duty starter solenoid. The "s" = terminal label is for start. The "i" terminal label is for ignition. The = "i" terminal shorts out the ignition ballast resistor in a breaker point = ignition from the old days. The plastic coil melted because the relay = was held on too long. The add from snap jack is aimed at small mass relays. The usual snubber = diode technique common in our airplanes slows the collapse of the relay = magnetic field which slows the contact break action. Slowing the break = action in a small relay will increase contact arcing which shortens the = life of the relay when used near it's maximum rating with an inductive = load. The large solenoid type relays we use will not benefit from the = snap jack since the break is dominated by the mass of the moving contact = rather than the collapse of the magnetic field. A note of caution with the snap jack decision. The snubber is in place = to prevent the arcing of the contacts which energize the solenoid = (pressure sensor, microswitch, etc.). The snubber used must keep the = voltage below 35 volts to be effective so if you decide to use the snap = jack be sure it specifies a clamp voltage below 35 volts. For those with = 24 volt systems, I would suggest not using the snap jack since the clamp = voltage is nearly the same as the the system voltage and no benefit is = realized. As you might be able to infer from this... I suggest the use of the = simple diode with the precaution that the polarity be correct. Feel free to shoot me an email if further comment will help. Jack Morgan On Apr 19, 2013, at 6:00 AM, Lancair Mailing List wrote: > From: "Greenbacks, UnLtd." > Subject: 320/360 intermittent duty relay > Date: April 18, 2013 2:56:12 PM EDT > To: List Lancair Mailing >=20 >=20 > Had an opportunity today to dissect the failed relay on the low = pressure side of my system. > Clearly there had been arcing between the load terminals and the = contactor bar but more interestingly, > the plastic which surrounds the magnet had begun to melt and crack. = This prevented the contactor bar shaft from sliding > freely when the magnet was energized..... >=20 > So, at the risk of displaying my normal electrical ignorance, which = diagram below best represents > the intermittent relays in our 320/360s? My relays are grounded at the = case and have two small terminals > on the side marked "I" and "S". Voltage applied to the "S" terminal = will energize the relay. >=20 > In this illustration from the Perhgelion Design website, it looks like = the 2nd diagram from the left best represents what we > have. So placing a Bi-directional Zenner diode between the "S" = terminal and the case ground is all that's needed > to protect the relay control circuit, right?? But what about the fat = contactor load terminals and the bar inside the relay, how can or should = they=20 > be protected as well? Does it make sense to place a Bi-directional = Zenner diode across these terminals as well? >=20 > See, your suspicion that I don't have EE after my name is confirmed! >=20 > Angier Ames > N4ZQ > 22hrs > --Apple-Mail=_B8A84477-0D7E-4BAA-A427-A3F2EAA9CD94 Content-Transfer-Encoding: quoted-printable Content-Type: text/html; charset=iso-8859-1 The = failed relay is an intermittent duty starter solenoid. The "s" terminal = label is for start. The "i" terminal label is for ignition. The "i" = terminal shorts out the ignition ballast resistor in a breaker point = ignition from the old days. The plastic coil melted because the relay = was held on too long.

The add from snap jack is aimed = at small mass relays. The usual snubber diode technique common in our = airplanes slows the collapse of the relay magnetic field which slows the = contact break action. Slowing the break action in a small relay will = increase contact arcing which shortens the life of the relay when used = near it's maximum rating with an inductive load. The large solenoid type = relays we use will not benefit from the snap jack since the break is = dominated by the mass of the moving contact rather than the collapse of = the magnetic field.

A note of caution with the = snap jack decision. The snubber is in place to prevent the arcing of the = contacts which energize the solenoid (pressure sensor, microswitch, = etc.). The snubber used must keep the voltage below 35 volts to be = effective so if you decide to use the snap jack be sure it specifies a = clamp voltage below 35 volts. For those with 24 volt systems, I would = suggest not using the snap jack since the clamp voltage is nearly the = same as the the system voltage and no benefit is = realized.

As you might be able to infer from = this... I suggest the use of the simple diode with the precaution that = the polarity be correct.

Feel free to shoot me = an email if further comment will help.

Jack = Morgan

On Apr 19, 2013, at 6:00 AM, Lancair = Mailing List wrote:

From: "Greenbacks, = UnLtd." <n4zq@verizon.net>
=
Subject: 320/360 = intermittent duty relay
Date: April 18, 2013 = 2:56:12 PM EDT
To: List Lancair = Mailing <lml@lancaironline.net>


Had an opportunity today to dissect the failed relay = on the low pressure side of my system.
Clearly there had been arcing = between the load terminals and the contactor bar but more = interestingly,
the plastic which surrounds the magnet had begun to = melt and crack. This prevented the contactor bar shaft from = sliding
freely when the magnet was energized.....

So, at the = risk of displaying my normal electrical ignorance, which diagram below = best represents
the intermittent relays in our 320/360s? My relays = are grounded at the case and have two small terminals
on the side = marked "I" and "S". Voltage applied to the "S" terminal will energize = the relay.

In this illustration from the Perhgelion Design = website, it looks like the 2nd diagram from the left best represents = what we
have. So placing a Bi-directional Zenner diode between the = "S" terminal and the case ground is all that's needed
to protect the = relay control circuit, right?? But what about the fat contactor load = terminals and the bar inside the relay, how can or should they 
be protected as well? = Does it make sense to place a Bi-directional Zenner diode across these = terminals as well?

See, your suspicion that I don't have EE after = my name is confirmed!

Angier = Ames
N4ZQ
22hrs
<Zener.jpg><zener-1.j= pg>

= --Apple-Mail=_B8A84477-0D7E-4BAA-A427-A3F2EAA9CD94--