---------------------------------------------------------- AeroElectric-List Digest Archive --- Total Messages Posted Fri 01/30/09: 3 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 05:51 AM - Re: Switches and Relays (Peter Laurence) 2. 04:29 PM - Re: Switches and Relays (Robert L. Nuckolls, III) 3. 07:19 PM - Re: Switches and Relays (Vern Little) ________________________________ Message 1 _____________________________________ Time: 05:51:19 AM PST US From: "Peter Laurence" Subject: RE: AeroElectric-List: Switches and Relays Vern, About 4 years and 500 hundred hours ago, I wired a velocity for a friend as per Bob's Z drawings. I too was hesitant about running large wires up the door post to the overhead switch gang. I made a box with post terminals in the box and a gang of 13 relays on top. This was mounted on the forward bulkhead close to the battery. Have not had to replace a relay yet. However he does keep a couple of spares in the plane. Peter Laurence RV9A N60PL I've looked at this in some detail. Since I've had multiple switch failures (long Carling switch thread), I have looked at relays for switching heavy loads. In my new A/C (Harmon Rocket), this thinking has led me to a bank of relays controlled by grounded switches. I need a bunch of relays for the trim systems and other stick-grip switches anyway, so I went all the way with all of my electrical loads switched with relays. While not strictly necessary, it allowed me to place the relays and breakers off-panel where the heavy gauge wiring runs were shorter. This saves many dozens of feet of heavy wiring running back and forth to the panel. Most of the switches on the panel are grounded to activate the corresponding relay. This allows me to use a single 22 AWG wiring for each relay control. I can also use lighter weight toggle switches on the panel, which also happen to be cheaper. The lighter weight switches and shorter heavy gauge wiring runs should roughly balance out the relay weights. Another benefit of this approach is that rotary switches can be used instead of toggles. For example, I plan one rotary switch for my main lights: OFF-WIGWAG-PULSE-LDG-TAXI-BOTH. This takes one position on my panel and is configured to drive my two lamp relays as necessary (left and right wingtip lamps). Also, I plan on connectorizing the panel... it's a lot simpler with fewer light gauge wires. So an architecture based on relays has other benfits other than protecting switches. These benefits must be weighed against the complexity and potential failure modes of relays compared to switches. Sometimes, you just want to experiment! Vern Little ________________________________ Message 2 _____________________________________ Time: 04:29:52 PM PST US From: "Robert L. Nuckolls, III" Subject: RE: AeroElectric-List: Switches and Relays At 10:13 PM 1/29/2009, you wrote: > >Bob, > >Speaking of switch failures, > >I think you had mentioned that you would test the practicality and function >of adding JB weld to switch rivets to see if it would prevent them from >loosening without a downside. Any progress there? Some. I have looked at every riveted Carling switch in the shop (about 25 pcs) and found none with observably loose joints. I did do some tests to determine that the contact material (which includes the formed rivet head) is solderable - as are the brass fast-on tabs. The conditions are favorable soldering the rivets to the tabs and then covering the joint with a dab of JB Weld. This still begs the question as to return on investment for this effort. We've identified no changes to process or design that would account for a rash of failures in these switches. The design has been essentially unchanged for decades and what must be many millions of devices. I'll suggest it's pretty clear that the failures were not a function of failure to observe ratings. It's clear that the strongest potential for failure happens under the formed head of the rivet. If it's too loose, corrosion can begin and failure is a sure thing given sufficient time. The soldering process is not a quick-n-easy thing. I was able to get good flow to the two materials but it was a bit fussy. Couldn't be sure that I wasn't degrading the joint quality at the base of the saddle inside the switch while I was making them "better" on the outside. If you've got switches that are not yet installed, it wouldn't hurt to beef them up with some JB Weld. Use the slow setting stuff so you've got plenty of time to work carefully. You can also mix up a larger quantity of the slow stuff and do a batch of switches. Emacs! Take care to avoid contaminating the tabs. I'm not confident that soldering the contact to the tabs is an "improvement". The epoxy beef-up can't hurt anything and it may be helpful. Bob . . . ----------------------------------------) ( . . . a long habit of not thinking ) ( a thing wrong, gives it a superficial ) ( appearance of being right . . . ) ( ) ( -Thomas Paine 1776- ) ---------------------------------------- ________________________________ Message 3 _____________________________________ Time: 07:19:00 PM PST US From: "Vern Little" Subject: Re: AeroElectric-List: Switches and Relays Thanks for the reference Peter. I too plan to have a spare relay or too handy (or I could swap out a non-critical one such as Pitot Heat or Nav Lights) for emergencies. I have relays with interlocking sockets that connect together. This should make for a stable mounting system. Vern ----- Original Message ----- From: "Peter Laurence" Sent: Friday, January 30, 2009 5:10 AM Subject: RE: AeroElectric-List: Switches and Relays > > > > Vern, > > About 4 years and 500 hundred hours ago, I wired a velocity for a friend > as > per Bob's Z drawings. I too was hesitant about running large wires up the > door post to the overhead switch gang. > > I made a box with post terminals in the box and a gang of 13 relays on > top. This was mounted on the forward bulkhead close to the battery. > > Have not had to replace a relay yet. However he does keep a couple of > spares > in the plane. > > > Peter Laurence > RV9A N60PL > > > I've looked at this in some detail. Since I've had multiple switch > failures > > (long Carling switch thread), I have looked at relays for switching heavy > loads. > > In my new A/C (Harmon Rocket), this thinking has led me to a bank of > relays > controlled by grounded switches. I need a bunch of relays for the trim > systems and other stick-grip switches anyway, so I went all the way with > all > > of my electrical loads switched with relays. While not strictly > necessary, > it allowed me to place the relays and breakers off-panel where the heavy > gauge wiring runs were shorter. This saves many dozens of feet of heavy > wiring running back and forth to the panel. > > Most of the switches on the panel are grounded to activate the > corresponding > > relay. This allows me to use a single 22 AWG wiring for each relay > control. > > I can also use lighter weight toggle switches on the panel, which also > happen to be cheaper. The lighter weight switches and shorter heavy gauge > wiring runs should roughly balance out the relay weights. > > Another benefit of this approach is that rotary switches can be used > instead > > of toggles. For example, I plan one rotary switch for my main lights: > OFF-WIGWAG-PULSE-LDG-TAXI-BOTH. This takes one position on my panel and > is > configured to drive my two lamp relays as necessary (left and right > wingtip > lamps). Also, I plan on connectorizing the panel... it's a lot simpler > with > > fewer light gauge wires. > > So an architecture based on relays has other benfits other than protecting > switches. These benefits must be weighed against the complexity and > potential failure modes of relays compared to switches. Sometimes, you > just > > want to experiment! > > Vern Little > > > ------------------------------------------------------------------------------------- Other Matronics Email List Services ------------------------------------------------------------------------------------- Post A New Message aeroelectric-list@matronics.com UN/SUBSCRIBE http://www.matronics.com/subscription List FAQ http://www.matronics.com/FAQ/AeroElectric-List.htm Web Forum Interface To Lists http://forums.matronics.com Matronics List Wiki http://wiki.matronics.com Full Archive Search Engine http://www.matronics.com/search 7-Day List Browse http://www.matronics.com/browse/aeroelectric-list Browse Digests http://www.matronics.com/digest/aeroelectric-list Browse Other Lists http://www.matronics.com/browse Live Online Chat! http://www.matronics.com/chat Archive Downloading http://www.matronics.com/archives Photo Share http://www.matronics.com/photoshare Other Email Lists http://www.matronics.com/emaillists Contributions http://www.matronics.com/contribution ------------------------------------------------------------------------------------- These Email List Services are sponsored solely by Matronics and through the generous Contributions of its members.