---------------------------------------------------------- AeroElectric-List Digest Archive --- Total Messages Posted Tue 06/03/14: 11 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 12:39 AM - Re: Info on MGL Enigma (Jay Hyde) 2. 03:36 AM - Off Delay Cabin Light (user9253) 3. 05:24 AM - Re: Off Delay Cabin Light (Charlie England) 4. 05:55 AM - Economical solid state pressure sensors (Ken) 5. 06:41 AM - Re: Info on MGL Enigma (Eric M. Jones) 6. 08:07 AM - Re: Bonding Straps (Robert L. Nuckolls, III) 7. 08:54 AM - Re: Bonding Straps (stearman456) 8. 11:23 AM - Re: Economical solid state pressure sensors (Robert L. Nuckolls, III) 9. 12:00 PM - Re: Info on MGL Enigma (Robert L. Nuckolls, III) 10. 12:05 PM - Re: Re: Bonding Straps (Robert L. Nuckolls, III) 11. 01:24 PM - Re: Re: Bonding Straps (Daniel Jones) ________________________________ Message 1 _____________________________________ Time: 12:39:14 AM PST US From: "Jay Hyde" Subject: RE: AeroElectric-List: Info on MGL Enigma Hello again listers, Here is a further response from Rainier: I did not say that spikes or similar ARE the cause of what it going on. It might be something completely unrelated. It's a pretty complex system. There are no old style linear regulators in the system. There are three high frequency switch mode supplies and all input power is protected by a heavy duty transorb apart from other filtering (mostly inductive/capacitive). Nevertheless, we are talking about a system that has multiple connectivity to other electrical systems on the aircraft - anything going on anywhere and the EFIS gets it. We are taking about transient events at RF frequencies. Do-160 simply does not cater for this on a long term bases. But that is another story. So, honestly, without actually having the system on a bench and investigating - and conclusively finding the cause, going on like that is not called for here. Getting back to the Flash memory - yes it does fail if it gets transient power events that make it through the system by whatever path. It may take years. However that is by no means the only possible cause. Flash is known to wear over time. Manufacturers of these devices guarantee 10 years of data retention typically, even if no writes take place - yet these devices are used throughout the industry for missions where it is assumed that they will never fail. Usually they don't. In this case we don't even know if this memory has failed. It might be something else - perhaps the communications link between main CPU and the processor that contains this memory has gone faulty. It could be anything. I'm guessing. That is all I can do without having the Enigma on my bench. Electronics do fail - does not matter how much money you spend on the components. Service history of the Enigma has been excellent. The number of Enigmas coming back to the factory for repairs is almost nil. That is not too surprising - it has been designed for open cockpit ultralights and it is quite tough. But they are getting older now and failures of electronic components become more of a factor. There is something called a "bathtub failure curve" - because it looks like it. Failures tend to occur when the device is new (partly the reason we run them for 48 hours at elevated temperatures during manufacture) - then things settle down and after some time failure rates start creeping up slowly as things age. Components that do age are crystals (They are mechanical devices - high frequency types in particular have a higher failure rate in our experience). Then we have ceramic capacitors - a typical EFIS has hundreds of them. Some start leaking after a while. Most of the time that is not an issue but sometimes it is. We don't use tantalums because of reliability concerns (good caps but they have an annoying tendency to blow up). Our electrolytics are top quality devices - can't even remember any failures. Then we get to the semiconductors. Well, here we have a pretty random failure pattern. They do die for no apparent reason. The rate is low but it does happen. Yes, we use aerospace, automotive and industrial spec devices - we do not use consumer graded devices at all. Most failures are perhaps related to PCB failures (usually thermal stress cracking vias). Some of our PCBs are high tech multi-layer. They are more sensitive - part of the process. Some assemblies are lead free and the entire industry has been battling for years with "tin-wiskers". Microscopic growths of tin between tracks and pads. Only visible under a microscope. Takes years to cause a problem. That we have had. Lucky this is not so much of an issue anymore as lead free processes and fluxes have improved and I have yet to see such an issue on anything produced in the last 4 or 5 years. "Cold solder joints" - that happens either via repeated thermal stress cracking a solder joint or a manufacturing defect that may take years to manifest itself. Yes, it happens. It passes all tests and optical quality controls (we use an automated AOI machine plus visual checks at various stages during the assembly process) - yet it still manages to avoid early detection. Sure, the rate is low but we make thousands of devices every month. Including devices not intended for aircraft (and not under our brand name). I would love a zero failure rate. Failures are bad. Everybody gets annoyed - from the customer to us. We can't have a zero failure rate - that is a pipe dream. But we can always work to reduce it to the barest minimum. If we did not do that we'd be out of business long ago. Most of our repairs are directly related to what we call "blow ups". Reverse polarity issues, connecting power or grounds to the wrong places etc. Interface driver chips (RS232, CAN, switches etc) blown for various reasons - the items directly connected to the outside World. All of that happens typically during installation. Mostly with the so called "professional installers, AMOs etc". I'm not kidding. We find the home builders are the ones with the least issues - perhaps because most take the time to study the docs and plan their wiring. There is no rush, no deadlines. That helps. Our statistics (which we do keep for obvious reasons) shows this trend very clearly. Instruments get dropped, might have a hard time during transport - sometimes they get soaked in water or oil. Anyway, I can't really comment on this Enigma until I see it myself (if that ever happens). If there is a problem, whatever the cause may be - we can fix it. That is the bottom line. Rainier -----Original Message----- From: owner-aeroelectric-list-server@matronics.com [mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Robert L. Nuckolls, III Sent: 02 June 2014 03:45 PM Subject: RE: AeroElectric-List: Info on MGL Enigma --> At 04:02 AM 6/2/2014, you wrote: Here is the reply from Rainier, the owner and founder of MGL: The CR2032 battery is only used to maintain items that change frequently like calculated fuel levels, local pressure settings etc. Setup is stored in a flash memory section of a secondary processor chip in the EFIS. This does not need a backup battery. If setup data stored here is not maintained there is usually only one cause: The supply voltage to that processor is raised briefly (micro-seconds to mill-seconds) above about 8V. This can happen if the supply to the EFIS contains sharp voltage spikes (typically caused by bad regulators or high voltage ignition is coupling into ground or supply). This can also happen if there are static discharges typically caused by airflow over metal parts that are not grounded. Eventually, this will damage the flash memory which is the part that dies first in our experience. When this happens we replace the processor chip. If you have a techie handy - it is a type ATMEL ATMega128. It is a SMD package but easy to solder/desolder if you have the experience. Once replaced I would also recommend replacing the 16Mhz crystal right next to this chip - it tends to wear out over a long time (we replace these as a matter of course when we get an Enigma in for repairs). No specific programming of the new processor needs to be done as the firmware will detect a new processor and do the programming and setup of this chip automatically (the first start-up will take a bit longer and you will see some messages on the display to this effect). I am exceedingly skeptical of these assertions. I don't know of a single 5v regulator offered to the task of conditioning power for electronics that doesn't handily mitigate any of the commonly known variables on the ship's bus. DO-160 offers a clear and concise path to living confidently in the world of DC powered vehicles. Crystals that 'wear out'? Static discharges ? ! ? ! . . . again, for any piece of hardware to be qualified for installation on a TC aircraft, it has to be capable of withstanding discharges of a 150pF capacitor through 330 ohm resistor fed directly to every input/output pin on the device under test. TEN times for positive spikes, TEN more times for negative spikes. Sound brutal . . . but the components and architecture for designing to this level of stress is rudimentary and has been as common to the designer's toolbox as a hammer is to a carpenter's toolbox. I quit doing the test 25 years ago after learning what it took to pass . . . easily . . . every time. If the stresses cited are genuine risks to MGL's products, then they've failed to understand and embrace the real world stresses found in mobile DC powered system of all stripe . . . not the least of which are airplanes. Bob . . . ________________________________ Message 2 _____________________________________ Time: 03:36:54 AM PST US Subject: AeroElectric-List: Off Delay Cabin Light From: "user9253" The July 2014 issue of Kitplanes Magazine has an article by Jim Weir describing a circuit to delay turning off a light after the master switch is shut off. http://www.kitplanes.com/issues/31_7/builder_spotlight/aero_lectrics_july_2014_21035-1.html There is no power wire connected to Vcc pin 8 of the 555 IC. Was a wire inadvertently left off or will the circuit work as drawn? Joe -------- Joe Gores Read this topic online here: http://forums.matronics.com/viewtopic.php?p=424276#424276 ________________________________ Message 3 _____________________________________ Time: 05:24:13 AM PST US Subject: Re: AeroElectric-List: Off Delay Cabin Light From: Charlie England Perhaps it's been fixed; the online version has the connection. On Tue, Jun 3, 2014 at 5:35 AM, user9253 wrote: > > The July 2014 issue of Kitplanes Magazine has an article by Jim Weir > describing a circuit to delay turning off a light after the master switch > is shut off. > > http://www.kitplanes.com/issues/31_7/builder_spotlight/aero_lectrics_july_2014_21035-1.html > There is no power wire connected to Vcc pin 8 of the 555 IC. Was a wire > inadvertently left off or will the circuit work as drawn? > Joe > > -------- > Joe Gores > > > Read this topic online here: > > http://forums.matronics.com/viewtopic.php?p=424276#424276 > > ________________________________ Message 4 _____________________________________ Time: 05:55:38 AM PST US From: Ken Subject: AeroElectric-List: Economical solid state pressure sensors I only seem to get a few hundred hours out of name brand electromechanical engine pressure sensors so I tried a 30 psi $25. solid state Chinese sensor for coolant pressure monitoring. Quite a bit cheaper than what I was using and seemingly good specifications which I've copied below. While it calibrates perfectly at room temperature, it reads at least 5 psi low when it gets hot (ie. 4 psi when it should be 9). The zero point changes similarly and I confirmed all this with raw voltage readings and scope traces to make certain. This sensor was mounted on the firewall and tee'd into a 5/16" coolant hose so the coolant likely warmed it up to about 80*C. Seems it would need to be installed on a stub line on the cool side of the firewall to be useful. The temperature specification of Maximum:0.05%FS/C would indicate up to 1.5 psi zeroing error over a 100*C range which would be acceptable to me if that was the case and other errors were minor. This particular sensor may be outside of stated tolerances. In any case, the compensation temperature range of -20 to +80*C seems to be meaningless. I'd also hoped to replace the oil pressure sensor but it seems these economical sensors are not the answer for under the cowl. Ken Brand new pressure transducer. 316 Stainless steel body. Input: 0-30 psi(Gauge Pressure); Output: 0.5-4.5V linear voltage output. 0 psi outputs 0.5V, 15 psi outputs 2.5V, 30 psi outputs 4.5V. Works for oil,fuel or air pressure.Can be used in oil tank,gas tank,diesel tank etc. Accuracy: +/-1%FS; Thread: 1/8 NPT; Wiring Connector: Packard plug-in unit is included; Wiring: Red: +5V; Black: ground; Green: signal output; It's an advance pressure sender than traditional mechanical pressure sender; Overload Capacity: 2-4 times; Working Temperature: -40+120C; Compensation Temperature: -20+80C; Protection Class: IP67; Pressure Medium: The gas and liquid which is compatible with 316L stainless steel; Load Resistance: ((supply power-6.5V/0.02A); Long-term stability: Less than 0.1%FS/year; Temperature Effect on Zero: Typical:0.02%FS/C; Maximum:0.05%FS/C; Temperature Effect on Sensitivity: Typical:0.02%FS/C; Maximum:0.05%FS/C; Shock Resistance: 1000g; Anti-Shock: +/-0.01%FS(X,Y,Z axes, 200Hz/g); Response Time: 1ms; Insulation Resistance: >100m 500VDC; Weight: 55g; Explosion-proof Class: ExiaTTCT6; Electromagnetism Compatibility: EN50051-1. ________________________________ Message 5 _____________________________________ Time: 06:41:39 AM PST US Subject: AeroElectric-List: Re: Info on MGL Enigma From: "Eric M. Jones" It is hard to say that a 3V battery measuring 2.9V is dead or not depending on load. The nominal discharge current of the battery is 0.2 mA. Putting a 150k in parallel will show 2.9V or above for a still good battery. But since getting there is half the work, change it. http://www.adafruit.com/datasheets/maxell_cr2032_datasheet.pdf See DX.com (Deal Extreme) for a 10 pack of Sony 3V CR2032 Lithium Ion $5.98. Free shipping -------- Eric M. Jones www.PerihelionDesign.com 113 Brentwood Drive Southbridge, MA 01550 (508) 764-2072 emjones(at)charter.net Read this topic online here: http://forums.matronics.com/viewtopic.php?p=424294#424294 ________________________________ Message 6 _____________________________________ Time: 08:07:27 AM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Bonding Straps At 12:26 PM 6/2/2014, you wrote: > >In a mixed construction airplane (steel tube fuselage, wooden wings, >aluminum structure flight controls, everything fabric covered) what >would the down side be in not having everything electrically >bonded? My electrical system is a two wire, 14v system with >everything running to a "forest of tabs" ground bus on the >firewall. The avionics (SL40 com, GTX 327 txdr) run to their own, >dedicated ground bus which in turn is wired to the firewall ground >bus. I'm doing the bonding per the original design, but I'm just >curious. Would all the various assemblies of the airplane create >static charges that would cripple the radios? > >Dan Bonding for static control, grounding for power distribution and grounding for antenna performance are largely separate issues. P-static is not an issue for low speed aircraft cruising in the lower atmospheres. Sounds like you've got the lights lit up so the only thing left is to provide adequate ground planes under antennas. But in no case is there value in tying every 'grounded' device to all other grounded devices. Bob . . . ________________________________ Message 7 _____________________________________ Time: 08:54:08 AM PST US Subject: AeroElectric-List: Re: Bonding Straps From: "stearman456" Thanks Bob. Would there be any value in tying the avionics ground bus directly to the battery instead of to the main ground bus? (Putting the two ground buses in parallel instead of in series). Read this topic online here: http://forums.matronics.com/viewtopic.php?p=424303#424303 ________________________________ Message 8 _____________________________________ Time: 11:23:39 AM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Economical solid state pressure sensors At 07:55 AM 6/3/2014, you wrote: I only seem to get a few hundred hours out of name brand electromechanical engine pressure sensors so I tried a 30 psi $25. solid state Chinese sensor for coolant pressure monitoring. Quite a bit cheaper than what I was using and seemingly good specifications which I've copied below. While it calibrates perfectly at room temperature, it reads at least 5 psi low when it gets hot (ie. 4 psi when it should be 9). The zero point changes similarly and I confirmed all this with raw voltage readings and scope traces to make certain. This sensor was mounted on the firewall and tee'd into a 5/16" coolant hose so the coolant likely warmed it up to about 80*C. Seems it would need to be installed on a stub line on the cool side of the firewall to be useful. The temperature specification of Maximum:0.05%FS/C would indicate up to 1.5 psi zeroing error over a 100*C range which would be acceptable to me if that was the case and other errors were minor. This particular sensor may be outside of stated tolerances. In any case, the compensation temperature range of -20 to +80*C seems to be meaningless. I'd also hoped to replace the oil pressure sensor but it seems these economical sensors are not the answer for under the cowl. I have one of those transducers in a 300 psi version . . . in fact . . . it's in my pocket right now. We ordered it in to consider for a future development program. I'll see if I can get a quick look-see on accuracy and temperature effects. The numbers you're citing are pretty poor . . . I can't imagine anyone putting so much into a stainless case and cutting short the electronics . . . electronics that are pretty much jelly-bean parts. If you're going to round-file the aberrant transducer, drop it to me in the mail . . . I'd like to peek at it on the bench too. Bob . . . ________________________________ Message 9 _____________________________________ Time: 12:00:37 PM PST US From: "Robert L. Nuckolls, III" Subject: RE: AeroElectric-List: Info on MGL Enigma At 02:37 AM 6/3/2014, you wrote: Hello again listers, Here is a further response from Rainier: I did not say that spikes or similar ARE the cause of what it going on. It might be something completely unrelated. It's a pretty complex system. . . . then why even mention it? The customer does not benefit from a narration of possible causes . . . especially when those causes include things that 'might' be wrong with his airplane. But to assert that stresses external to the product's enclosure can zap a micro-controller does nothing to engender confidence in the rest of hardware under the best of circumstances. There are no old style linear regulators in the system. There are three high frequency switch mode supplies and all input power is protected by a heavy duty transorb apart from other filtering (mostly inductive/capacitive). Electronics do fail - does not matter how much money you spend on the components. Service history of the Enigma has been excellent. The number of Enigmas coming back to the factory for repairs is almost nil. When we conduct a reliability study on an assembly, powers-that-be don't really start smiling until your aggregate MTBF drops below 1 x 10 minus 7 failures per flight hour. For critical systems 1 x 10 minus 9 is the target. So if your device has 100 components in it, INDIVIDUAL failure rates have to be 100x better than the aggregate. If this guy has crystals that warrant routine replacement base on some fielded experience . . . he is well advised to change brands. intended for aircraft (and not under our brand name). I would love a zero failure rate. Failures are bad. Everybody gets annoyed - from the customer to us. We can't have a zero failure rate - that is a pipe dream. But we can always work to reduce it to the barest minimum. If we did not do that we'd be out of business long ago. Most of our repairs are directly related to what we call "blow ups". Reverse polarity issues, connecting power or grounds to the wrong places etc. Interface driver chips (RS232, CAN, switches etc) blown for various reasons - the items directly connected to the outside World. One cannot necessarily design every i/o port to withstand the vagaries of neophyte installations but failures of components not connected directly to the outside world is cause for concern. All of that happens typically during installation. Mostly with the so called "professional installers, AMOs etc". I'm not kidding. We find the home builders are the ones with the least issues - perhaps because most take the time to study the docs and plan their wiring. There is no rush, no deadlines. That helps. Our statistics (which we do keep for obvious reasons) shows this trend very clearly. Instruments get dropped, might have a hard time during transport - sometimes they get soaked in water or oil. Anyway, I can't really comment on this Enigma until I see it myself (if that ever happens). If there is a problem, whatever the cause may be - we can fix it. That is the bottom line. To be sure, nobody can offer "zero failure rates" but they can be exceedingly small. Builders anticipating operations over long stretches of unfriendly terrain or in IMC would be well advised to craft 'plan-b', 'plan-c' or whatever in the event the whole system goes belly-up. "Barest minimum" failure rates are un-quantified. If we had any hardware coming back from the field suffering some of the failures cited above . . . things around here would, shall we say, get very 'tense'? A display with this kind of data . .. Emacs! implies certain capabilities. Capabilities that require TC aircraft designers to go Level A software/hardware, careful partitioning of functions and probably dual screens. Do your own Failure Modes Effects Analysis based on how you need to use this hardware. Have a solid alternative for every situation when it isn't working. Bob . . . ________________________________ Message 10 ____________________________________ Time: 12:05:13 PM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Re: Bonding Straps At 10:52 AM 6/3/2014, you wrote: > >Thanks Bob. Would there be any value in tying the avionics ground >bus directly to the battery instead of to the main ground >bus? (Putting the two ground buses in parallel instead of in series). No . . . and especially not the battery(-) post. The battery is but one of many components that benefit by sharing a centralized ground but its (-) terminal point should not be that centralize ground location. If you have a panel ground for potential vicitims that is in turn tied ot the central ground on the fire wall, you're good to go. Bob . . . ________________________________ Message 11 ____________________________________ Time: 01:24:22 PM PST US From: Daniel Jones Subject: Re: AeroElectric-List: Re: Bonding Straps Ok - thanks. That was the way I understood it. ----- Original Message ----- From: Robert L. Nuckolls, III Sent: Tue, 03 Jun 2014 13:03:48 -0600 (MDT) Subject: Re: AeroElectric-List: Re: Bonding Straps At 10:52 AM 6/3/2014, you wrote: > >Thanks Bob. Would there be any value in tying the avionics ground >bus directly to the battery instead of to the main ground >bus? (Putting the two ground buses in parallel instead of in series). No . . . and especially not the battery(-) post. The battery is but one of many components that benefit by sharing a centralized ground but its (-) terminal point should not be that centralize ground location. If you have a panel ground for potential vicitims that is in turn tied ot the central ground on the fire wall, you're good to go. Bob . . . ------------------------------------------------------------------------------------- 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.