X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from omr-m04.mx.aol.com ([64.12.143.78] verified) by logan.com (CommuniGate Pro SMTP 6.0.4) with ESMTP id 6211592 for lml@lancaironline.net; Fri, 19 Apr 2013 14:53:41 -0400 Received-SPF: pass receiver=logan.com; client-ip=64.12.143.78; envelope-from=Sky2high@aol.com Received: from mtaomg-da06.r1000.mx.aol.com (mtaomg-da06.r1000.mx.aol.com [172.29.51.142]) by omr-m04.mx.aol.com (Outbound Mail Relay) with ESMTP id DB8B970004308 for ; Fri, 19 Apr 2013 14:53:08 -0400 (EDT) Received: from core-mtb005c.r1000.mail.aol.com (core-mtb005.r1000.mail.aol.com [172.29.234.209]) by mtaomg-da06.r1000.mx.aol.com (OMAG/Core Interface) with ESMTP id 97B43E000086 for ; Fri, 19 Apr 2013 14:53:08 -0400 (EDT) From: Sky2high@aol.com Full-name: Sky2high Message-ID: <59d7c.a38aa03.3ea2ec94@aol.com> Date: Fri, 19 Apr 2013 14:53:08 -0400 (EDT) Subject: Re: [LML] Relay snubber To: lml@lancaironline.net MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="part1_59d7c.a38aa03.3ea2ec94_boundary" X-Mailer: AOL 9.6 sub 168 X-Originating-IP: [67.175.156.123] x-aol-global-disposition: G DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=mx.aol.com; s=20121107; t=1366397588; bh=N+B5/6mSXs33spqyBqJ1hPftqPim50AAznMzsxiLp3U=; h=From:To:Subject:Message-ID:Date:MIME-Version:Content-Type; b=Td5dDkKQOgOzKgOk0r9j//bLgsJlos2y+X+ljDGzE0SD9/cSGgMixTT9ML8RDMUMK eaiLIYPaFye3sPhv6aINi+qf2KC5x2pV1HhntHFfREuEa/lbnC4TVRIJDczMzNY4aI PJezszYtmCVB0tYEZJ25Z4FGROtUqB/uuKpUU208= X-AOL-SCOLL-SCORE: 0:2:411384608:93952408 X-AOL-SCOLL-URL_COUNT: 0 x-aol-sid: 3039ac1d338e5171929431a0 --part1_59d7c.a38aa03.3ea2ec94_boundary Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit Uh, not quite Jack......... Yes, the intermittent relay failed (melted parts) because it was held in too long, but in the odd Lancair terminology environment: S = Switch (+12VDC, while the other side of the coil is grounded through the case) coming from the pressure switch and thence from the gear selection switch through the 5 A breaker/fuse that folks forget to pull when they pull the pump breaker whilst power is supplied from the main bus and the particular pressure is low enough to allow the pressure switch to make. I = Indicate = +12 VDC available as a tap off of the contactor plate when it makes the connection betwixt power and pump used to provide the positive voltage to the lamp on the console marked "pump in transition". And, yes, hopefully the 18 gauge wire running from the I-terminals will never short while the pump is engaged because it will try to carry hi amps up to those of the 50-60 A breaker covering the #10 wires used to power the pump through the relay. OH well....... Diode stuff is good.......... Grayhawk In a message dated 4/19/2013 12:46:57 P.M. Central Daylight Time, jmorgan1023@comcast.net writes: 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_ (mailto: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_ (mailto: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 = --part1_59d7c.a38aa03.3ea2ec94_boundary Content-Type: text/html; charset="US-ASCII" Content-Transfer-Encoding: quoted-printable
Uh, not quite Jack......... Yes, the intermittent relay failed (melted= =20 parts) because it was held in too long, but in the odd Lancair terminology= =20 environment:
 
S =3D Switch (+12VDC, while the other side of the coil is grounded thr= ough=20 the case) coming from the pressure switch and thence from the gear selectio= n=20 switch through the 5 A breaker/fuse that folks forget to pull when they pul= l the=20 pump breaker whilst power is supplied from the main bus and the particular= =20 pressure is low enough to allow the pressure switch to make.
 
I =3D Indicate =3D +12 VDC available as a tap off of the contactor pla= te when=20 it makes the connection betwixt power and pump used to provide  the=20 positive voltage to the lamp on the console marked "pump in transition".
 
And, yes, hopefully the 18 gauge wire running from the I-terminals wil= l=20 never short while the pump is engaged because it will try to carry hi = amps=20 up to those of the 50-60 A breaker covering the #10 wires used to power the= pump=20 through the relay.
 
OH well.......
 
Diode stuff is good..........
 
Grayhawk
 
In a message dated 4/19/2013 12:46:57 P.M. Central Daylight Time,=20 jmorgan1023@comcast.net writes:
= The=20 failed relay is an intermittent duty starter solenoid. The "s" terminal l= abel=20 is for start. The "i" terminal label is for ignition. The "i" terminal sh= orts=20 out the ignition ballast resistor in a breaker point ignition from the ol= d=20 days. The plastic coil melted because the relay was held on too long.=20

The add from snap jack is aimed at small mass relays. The usual snub= ber=20 diode technique common in our airplanes slows the collapse of the relay= =20 magnetic field which slows the contact break action. Slowing the break ac= tion=20 in a small relay will increase contact arcing which shortens the life of = the=20 relay when used near it's maximum rating with an inductive load. The larg= e=20 solenoid type relays we use will not benefit from the snap jack since the= =20 break is dominated by the mass of the moving contact rather than the coll= apse=20 of the magnetic field.

A note of caution with the snap jack decision. The snubber is in pla= ce to=20 prevent the arcing of the contacts which energize the solenoid (pressure= =20 sensor, microswitch, etc.). The snubber used must keep the voltage below = 35=20 volts to be effective so if you decide to use the snap jack be sure it=20 specifies a clamp voltage below 35 volts. For those with 24 volt systems,= I=20 would suggest not using the snap jack since the clamp voltage is nearly t= he=20 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= =20 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.= "=20 <n4zq@verizon.net>
Subject: 320/360 intermit= tent=20 duty relay
Date: April 18, 2013 2:56= :12 PM=20 EDT
To: List Lancair Mailin= g=20 <lml@lancaironline.net>
=


Had=20 an opportunity today to dissect the failed relay on the low pressure si= de of=20 my system.
Clearly there had been arcing between the load terminals = and=20 the contactor bar but more interestingly,
the plastic which surround= s the=20 magnet had begun to melt and crack. This prevented the contactor bar sh= aft=20 from sliding
freely when the magnet was energized.....

So, at= the=20 risk of displaying my normal electrical ignorance, which diagram below = best=20 represents
the intermittent relays in our 320/360s? My relays are=20 grounded at the case and have two small terminals
on the side marked= "I"=20 and "S". Voltage applied to the "S" terminal will energize the=20 relay.

In this illustration from the Perhgelion Design website, = it=20 looks like the 2nd diagram from the left best represents what we
hav= e. So=20 placing a Bi-directional Zenner diode between the "S" terminal and the = case=20 ground is all that's needed
to protect the relay control circuit, ri= ght??=20 But what about the fat contactor load terminals and the bar inside the= =20 relay, how can or should they 
be protected as well? Do= es it=20 make sense to place a Bi-directional Zenner diode across these terminal= s as=20 well?

See, your suspicion that I don't have EE after my name is= =20 confirmed!

Angier=20 Ames
N4ZQ
22hrs
<Zener.jpg><zener-= 1.jpg>

=3D
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