---------------------------------------------------------- AeroElectric-List Digest Archive --- Total Messages Posted Fri 09/05/08: 12 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 04:34 AM - Re: Switch problem (Robert L. Nuckolls, III) 2. 06:07 AM - Re: Switch problem (George, Neal E Capt USAF ACC 605 TES/TBM) 3. 09:56 AM - Relay coils and diodes (Ralph E. Capen) 4. 10:52 AM - ELT Mounting Bracket (JohnInReno) 5. 11:47 AM - Re: ELT Mounting Bracket (Bret Smith) 6. 12:30 PM - Re: ELT Mounting Bracket (John Morgensen) 7. 12:34 PM - Re: ELT Mounting Bracket (JohnInReno) 8. 01:02 PM - Re: Switch problem (Robert L. Nuckolls, III) 9. 03:17 PM - Re: Relay coils and diodes (Robert L. Nuckolls, III) 10. 03:32 PM - Re: ELT Mounting Bracket (Ron Quillin) 11. 04:20 PM - Re: Switch problem (Vernon Little) 12. 10:37 PM - Re: Switch problem (Gary Lineberry) ________________________________ Message 1 _____________________________________ Time: 04:34:28 AM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Switch problem At 02:10 PM 9/4/2008 -0700, you wrote: >Interestingly I have had almost the same problem. With a little over 200 >hours on the aircraft my Whelen strobe system stopped working. It did not >open the 10A fuse, but when switched on the strobes would flash for about >10 seconds and then stop. I was thinking that it was a problem with the >Whelen unit but it is in a very difficult place to get to in my RV8 (under >the floor) so I haven t yet gone to the effort to take up the floor to >check it out. I looked at the fuse block and things looked good. Until I >read this thread I didn t think about looking at the switch&..my mistake. Not a mistake . . . just an unhappy discovery that one ingredient in your system's recipe for success may not be performing as-advertised. > When I examined the switch today I discovered that the blue insulation > on the Fast-On connectors had darkened considerably, indicating that they > have been getting hot. They are still firmly attached to the wire but it > appears there is an internal problem in the switch that is causing > excessive heat. A logical deduction. >It is the B&C 1-3 switch referenced in this discussion. I have just >ordered a few of the Honeywell switches from Digi-Key and will replace it >with one of those. I'd really like to put my hands on the overheated switch for teardown, documentation and analysis. >I don t know what the actual current draw on the circuit is, but I have a >10A fuse that has not opened, so I would think that the B&C switch should >handle it. On the other hand, it appears that there is some other factor >afoot here in the strobe circuit that the 1-3 does not like. We ll see >how the Honeywell switch handles it. Agreed. There are valuable experiments to conduct for the purpose of clearer understanding. It's interesting to see how the act of bringing one event to forums like these triggers a cascade of recollection and consideration of similar events. Situations that might have been pushed aside as isolated events for individuals but raise flags of common concerns for the group when the knowledge is pooled together. The strobe supply is unique among loads on the bus. For those of you who are interested, take a peek at: http://www.aeroelectric.com/Pictures/Curves/Strobe_Supply_Current.pdf This is the current plot on a small strobe system I was able to document some years ago. We were investigating the effectiveness of various filter techniques for the purpose of reducing the whining noise that some strobes put out onto the bus. The bottom two plots of this figure show the unfiltered supply current draw of the system at two different sample rates. Of particular interest is the fast rate plot (second one up). Here we can clearly see the modulation of on-current that is indicative of the audio rate switching of the high voltage power supply. The third plot was measured after a 10KuF capacitor was placed across the strobe supply leads. Note that the switching noise is for all practical purposes gone. The fourth plot is with one of the now discontinued audio noise filters from Radio Shack. It too proved to be an effective suppressor of the audio rate noise but note the little spike at the onset of current draw. This is a GREAT illustration of the potential for unintended consequences of an otherwise good thing. This spike is a ringing at the resonant frequency of the filter's inductor and capacitor. While the combination of components DID relieve us of the audio rate noise, it produces a new stimulus that might now be perceived as a once-per-flash "tick" at some other place in the system. Clearly, this experiment suggests that the stand-alone capacitor is effective and offers the least risk for unintended byproducts of an otherwise effective solution. Now the problem before us is one of discovering the energy signature that offends a switch that should be sufficient to the task based on its ratings. Neal, are you following this thread? We were discussing an experiment to deduce the suitability of smaller gage shielded wire when used as the connection between strobe supply and the flash-tubes. Any chance you could get your hands on a 'scope with digital data recording features like a Tek TDS2012? These new gee-whizz scopes plot .jpg screen shots AND ascii sample plots to a thumbdrive. REALLY slick. If you could get the current plots from your system the same time you do the flash intensity experiments, it might lend some insight as to why the switches that control the strobes are barfing. If push came to shove, I could mail you my 'scope for a few days to get the measurements. Let's talk about this. Another interesting piece of data from the plots I cited above. Note that the POWER required to run this little feller was 1.3 a-s per cycle x 14 volts or 18 watts. THIS is the number that drives your load analysis for the purpose of sizing batteries and alternators. Note that it is smaller than the value derived by simply multiplying bus votlage by peak current draw of 2.7 amps (38 watts). Bob . . . ________________________________ Message 2 _____________________________________ Time: 06:07:36 AM PST US Subject: RE: AeroElectric-List: Switch problem From: "George, Neal E Capt USAF ACC 605 TES/TBM" Neal, are you following this thread? I'm trying. The water's deep and I'm short. Any chance you could get your hands on a 'scope with digital data recording features like a Tek TDS2012? Maybe. I'll ask around and see what I can find. neal ________________________________ Message 3 _____________________________________ Time: 09:56:34 AM PST US From: "Ralph E. Capen" Subject: AeroElectric-List: Relay coils and diodes My experience - shared for mine and other's education and offering of opinion. This past weekend, I was working on the wiring of my flap position sensor for my two-speed elevator trim circuit. The two-speed trim circuit essentially switches a low speed set matronics governor for a high speed set one via a pair of 4PDT relays whenever the flaps come off the upstop. As I was testing the detector switch - I got 'bit' by something that felt like house current (done that too!). Not knowing what was going on, I repeated the test...with identical results. OK, break out some of Bob's literary work - read-up and put in some diodes across the power terminals of the coil. Re-reading made me think that in my case, the diodes may be even more important...in Bob's writings (Paraphrased) "the absence of the diode presents the opening switch with the spike"; in my case, I have a couple of things wired up within the master switch... I'm thinking that in my case the master switch would 'see' the spike...along with anything else that is left on when I turn off the master. I know that the 'real' airplane stuff should be able to live in this environment and should not produce this environment either - however in the OBAM world, I can put in non tso'd trim servos and indicators (of which I have had a couple of them mysteriously blow one of their indicator lights) which are pretty good gear as far as I'm concerned - they just haven't spent the money and gone through the certification process. Got the diodes and will be putting them in this weekend. Is it possible that I'm allowing a spike to wander around my electrical system by turning off the master with some of these relays energized? Your thoughts please, Ralph Capen ________________________________ Message 4 _____________________________________ Time: 10:52:40 AM PST US Subject: AeroElectric-List: ELT Mounting Bracket From: "JohnInReno" Why does the mount for the Ameri-King ELT have a "wedge" under the rearward end so that the radio is tilted 20 up in the back? John Morgensen RV-9A fuselage Grumman AA1B-150 -------- RV-9A - Fuselage Grumman AA1B-150 (RV-Trainer) Flying Read this topic online here: http://forums.matronics.com/viewtopic.php?p 2780#202780 ________________________________ Message 5 _____________________________________ Time: 11:47:39 AM PST US From: "Bret Smith" Subject: RE: AeroElectric-List: ELT Mounting Bracket It doesn't. Loosen the strap and slide the unit forward until it sits flat, then re-fasten the strap. Bret Smith RV-9A N16BL Blue Ridge, Ga www.FlightInnovations.com -----Original Message----- From: owner-aeroelectric-list-server@matronics.com [mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of JohnInReno Sent: Friday, September 05, 2008 1:51 PM Subject: AeroElectric-List: ELT Mounting Bracket --> Why does the mount for the Ameri-King ELT have a "wedge" under the rearward end so that the radio is tilted 20 up in the back? John Morgensen RV-9A fuselage Grumman AA1B-150 -------- RV-9A - Fuselage Grumman AA1B-150 (RV-Trainer) Flying Read this topic online here: http://forums.matronics.com/viewtopic.php?p 2780#202780 ________________________________ Message 6 _____________________________________ Time: 12:30:42 PM PST US From: John Morgensen Subject: Re: AeroElectric-List: ELT Mounting Bracket I should have included pictures the first time. This is the Ameri-King 451 406 ELT and the very first ELT that I have ever dealt with. There is a lip around the tray that completely surrounds the radio. The only way to move it forward would be to have the radio sit on the forward lip. See the attached pictures. Bret Smith wrote: > > It doesn't. Loosen the strap and slide the unit forward until it sits flat, > then re-fasten the strap. > > > Why does the mount for the Ameri-King ELT have a "wedge" under the rearward > end so that the radio is tilted 20 up in the back? > > > -------- > RV-9A - Fuselage > Grumman AA1B-150 (RV-Trainer) Flying > > > ________________________________ Message 7 _____________________________________ Time: 12:34:21 PM PST US Subject: AeroElectric-List: Re: ELT Mounting Bracket From: "JohnInReno" I should have included pictures the first time. This is the Ameri-King 451 406 ELT and the very first ELT that I have ever dealt with. There is a lip around the tray that completely surrounds the radio. The only way to move it forward would be to have the radio sit on the forward lip. See the attached pictures. JohnInReno wrote: > Why does the mount for the Ameri-King ELT have a "wedge" under the rearward end so that the radio is tilted 20 up in the back? > > John Morgensen > RV-9A fuselage > Grumman AA1B-150 -------- RV-9A - Fuselage Grumman AA1B-150 (RV-Trainer) Flying Read this topic online here: http://forums.matronics.com/viewtopic.php?p 2794#202794 Attachments: http://forums.matronics.com//files/img_1581_medium_117.jpg http://forums.matronics.com//files/img_1580_medium_151.jpg http://forums.matronics.com//files/img_1579_medium_580.jpg ________________________________ Message 8 _____________________________________ Time: 01:02:55 PM PST US From: "Robert L. Nuckolls, III" Subject: RE: AeroElectric-List: Switch problem At 08:02 AM 9/5/2008 -0500, you wrote: >TES/TBM" > > > Neal, are you following this thread? > >I'm trying. The water's deep and I'm short. > > Any chance you could get your hands on a 'scope with digital >data recording features like a Tek TDS2012? > >Maybe. I'll ask around and see what I can find. Thanks! Bob . . . ________________________________ Message 9 _____________________________________ Time: 03:17:36 PM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Relay coils and diodes At 12:54 PM 9/5/2008 -0400, you wrote: > > >My experience - shared for mine and other's education and offering of opinion. > >This past weekend, I was working on the wiring of my flap position sensor >for my two-speed elevator trim circuit. The two-speed trim circuit >essentially switches a low speed set matronics governor for a high speed >set one via a pair of 4PDT relays whenever the flaps come off the upstop. > >As I was testing the detector switch - I got 'bit' by something that felt >like house current (done that too!). Not knowing what was going on, I >repeated the test...with identical results. Yeah, been there, done that. In my case I got the fingers across the contacts of a cub-scout electric buzzer project that operated from 3 volts (two flashlight cells). The field collapse from the small buzzer solenoid coil was sufficient to give ME a buzz which caused me to drop the project thus damaging it. Unfortunately it was not my project and my schoolmate was pretty unhappy about it. Neither of us understood what happened or why . . . but he got a personal demonstration of the effect a few days later. Even after my Navy veteran electrician father explained it to us, we didn't really understand. >OK, break out some of Bob's literary work - read-up and put in some diodes >across the power terminals of the coil. > >Re-reading made me think that in my case, the diodes may be even more >important...in Bob's writings (Paraphrased) "the absence of the diode >presents the opening switch with the spike"; in my case, I have a couple >of things wired up within the master switch... I'm thinking that in my >case the master switch would 'see' the spike...along with anything else >that is left on when I turn off the master. > >I know that the 'real' airplane stuff should be able to live in this >environment and should not produce this environment either - however in >the OBAM world, I can put in non tso'd trim servos and indicators (of >which I have had a couple of them mysteriously blow one of their indicator >lights) which are pretty good gear as far as I'm concerned - they just >haven't spent the money and gone through the certification process. > >Got the diodes and will be putting them in this weekend. Is it possible >that I'm allowing a spike to wander around my electrical system by turning >off the master with some of these relays energized? No. First, while the voltages generated by magnetic field collapse on a relay or contactor can be pretty spectacular, the ENERGY they contain is small. Given that the voltage is proportional to rate-of-magnetic decay, it stands to reason that maximum rate occurs at minimum current or widest opening of contacts on the controlling switch. This is a long winded way of stating that the source impedance of the relay coil as an energy storage device is big . . . too big to propagate significant pulses of "spike" energy out onto the bus. Most accessories have some amount of capacitance right across the power input leads as filters. This capacitance alone is a huge energy sink to inductively stored spikes. Risks to anything other than the controlling switch due to magnetic field collapse has been greatly exaggerated and poorly understood. There is no reason to be concerned beyond the effects on the controlling device . . . even if the diodes are not present. Bob . . . ________________________________ Message 10 ____________________________________ Time: 03:32:39 PM PST US Subject: Re: AeroElectric-List: ELT Mounting Bracket From: Ron Quillin At 10:50 9/5/2008, you wrote: >Why does the mount for the Ameri-King ELT have a "wedge" under the >rearward end so that the radio is tilted 20 up in the back? Mount for a helo? They're at an angle... Ron Q. ________________________________ Message 11 ____________________________________ Time: 04:20:16 PM PST US From: "Vernon Little" Subject: RE: AeroElectric-List: Switch problem I checked the switch that I installed as a replacement for the one that I fried about 100 hours ago. No sign of external damage or discoloration on the new switch. My failed switch was installed in 2005, purchased somewhat earlier. I had two switches that had loose rivets, so I'm wondering if there was a QC problem with the Carling switches made about that time. It would be interesting to see the date codes on the failed switches. My failed switch says C0344 Mexico. My guess was this is a date code (44th week in 2003?). The one Bob analysed says 9936 Mexico on it. Vern -----Original Message----- From: owner-aeroelectric-list-server@matronics.com [mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Robert L. Nuckolls, III Sent: September 5, 2008 9:08 AM Subject: RE: AeroElectric-List: Switch problem --> At 08:02 AM 9/5/2008 -0500, you wrote: >--> 605 >TES/TBM" > > > Neal, are you following this thread? > >I'm trying. The water's deep and I'm short. > > Any chance you could get your hands on a 'scope with digital >data recording features like a Tek TDS2012? > >Maybe. I'll ask around and see what I can find. Thanks! Bob . . . ________________________________ Message 12 ____________________________________ Time: 10:37:09 PM PST US From: "Gary Lineberry" Subject: AeroElectric-List: RE: Switch problem Bob: Thank you for your analysis. I would have been happy to send you the offending switch, but I have already dismantled it in order to satisfy my curiosity. The only real visual sign was some arc pitting on the contact surfaces. I believe that over time this pitting caused a high resistance that did two things. First, there was a voltage drop across this resistance which in series with the strobe unit caused the unit to stop working because of reduced voltage. When that happened I shut the circuit off and did not use it anymore. Second, the resistance at the pitted contacts generated enough heat to discolor the blue insulation on the Fast-On connectors, but I caught it before any further heat damage occurred. The switch components looked normal except for the pitting. Nothing anywhere near the fried specimen you referenced earlier. I temporarily installed a new 1-3 switch today and ran the system for =BD hour and noticed no heat increase on the fasteners. But I wouldn=92t expect that until many switch actuations and subsequent pitting of the contacts. I will put the Honeywell switch in when it arrives and keep an eye on it. If it shows any signs of impending failure I will research a Mil-Spec switch that might be a good replacement. Gary Lineberry RV8 N18BL ------------------------------------------------------------------------------------- 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.