---------------------------------------------------------- AeroElectric-List Digest Archive --- Total Messages Posted Sat 04/24/10: 12 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 07:08 AM - Re: Big load on BAT BUS (Robert L. Nuckolls, III) 2. 08:08 AM - Re: Re: Big load on BAT BUS (Robert L. Nuckolls, III) 3. 08:20 AM - Re: Surface temperature sensor (Robert L. Nuckolls, III) 4. 08:23 AM - Re: Big load on BAT BUS (Ken) 5. 08:27 AM - Re: Proper SWR meter (Robert L. Nuckolls, III) 6. 09:07 AM - Re: Big load on BAT BUS (jonlaury) 7. 11:18 AM - Re: Surface temperature sensor (J. Mcculley) 8. 12:10 PM - Re: Proper SWR meter (earl_schroeder@juno.com) 9. 02:45 PM - Re: Re: Designing a circuit question (Mike Welch) 10. 07:31 PM - Z-12 Power Grid Behavior (Valin & Allyson Thorn) 11. 07:31 PM - Re: Surface temperature sensor (Robert L. Nuckolls, III) 12. 07:36 PM - Re: Re: Big load on BAT BUS (Robert L. Nuckolls, III) ________________________________ Message 1 _____________________________________ Time: 07:08:42 AM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Big load on BAT BUS At 01:31 AM 4/24/2010, you wrote: > >In an attempt to keep redundant critical items from the same bus, I >have placed the fuse (10-15 amp) for my EFI injectors on the Bat Bus. >However, this violates BoB N's limit of Then you need a "mini-contactor" at the battery bus as illustrated in Z-32, except that the feeder is for the EFI instead of the E-bus. It would be nice if it were a solid state relay. I believe Eric Jones still offers on. Bob . . . ________________________________ Message 2 _____________________________________ Time: 08:08:10 AM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Re: Big load on BAT BUS At 01:38 AM 4/24/2010, you wrote: > >Never mind about the SS sleeve question. It will only be a 10 gauge >wire and I will 18 ga fuselink it at the battery. This sounds like another "loose cannon" implementation of fusible links. Fusible links are ROBUST circuit protection and should never be used in an always-hot feeder from a battery. If you've attached a wire to a battery that calls for this kind of circuit protection, it should enjoy upstream, crew- controlled management of power. As a general rule, please do not add fusible links to any application not already illustrated in the Z-figures without discussing it here on the List . . . and I can tell you in advance there's a 90+ percent chance that the proposed application is not recommended. Always-hot feeders should be breakered at 5A or less, fused at 7A or less. Anything larger should still take a fuse or breaker but CONTROLLED IMMEDIATELY ADJACENT to the bus with a relay like that shown in Z-32. Bob . . . ________________________________ Message 3 _____________________________________ Time: 08:20:12 AM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Surface temperature sensor At 09:38 PM 4/23/2010, you wrote: >Mcculley" > >Sorry Steve and others...I just thought this subject might be of >interest to so few that I should not take up >bandwith that those not interested would have to deal with. But, here it is: > > >This is a very accurate system that I tested with a laboratory quality >temperature meter and found the accuracy of all my sensors to be two >degrees F. It may not be very sophisticated, but it is super-inexpensive >and has never malfunctioned. I use it on every flight to assure myself >that no changes suddenly occur that could indicate a malfunction. > >Mine is about a $15 to $25 system that I've operated now for over seven >years and upwards of 600 flight hours on it's original internal >watch-size battery. The sensors are standard mini glass-encapsulated >thermistors available from most electronic supply sources. I used >Digi-Key # KC013-ND, 100k ohm units. How was it that you determined that the 100K devices were appropriate to your particular display? Folks should understand that there are hundreds of remote temperature measurement products on the market. I've see them use thermocouples, solid state LINEAR temperature sensors, diodes, the junctions of transistors (also a diode) AND thermistors. http://www.gesensing.com/products/resources/datasheets/ge1.pdf Thermistors are inexpensive AND rugged but they have the distinct disadvantage of being non-linear. So the accurate temperature display not only needs to know what the resistance of the device is at say 25C, the designer will compensate for the shape of temperature/resistance curve as well. The first thing one needs to do when adapting a commercial off the shelf (COTS) indicator to their airplane is to determine the sensor technology. If a thermistor, then you need to get the 25C resistance rating, and then the resistance at some other handy value (boiling water - 100C) and then find substitute sensors of identical characteristics. The really cool thing about the linear, solid state sensors is that they are direct reading, linear, and of known accuracy out of the box. I'm not discouraging anyone from exploring adaptation of any COTS temperature display but understand that there are some inviolate rules by which the sensing technology is identified and then duplicated so that the display performs as expected. Bob . . . ________________________________ Message 4 _____________________________________ Time: 08:23:19 AM PST US From: Ken Subject: Re: AeroElectric-List: Big load on BAT BUS There are details that aren't mentioned but I would be cautious with this. I'd only recommend an additional mini contactor if it is truly redundant and can't fail the engine. Risk from engine stoppage is likely far higher than the risk from electrical fire. Other considerations might be whether the EFI system already has a relay to supply injector power - many do have an ecu controlled relay that might be easily placed near the battery. Or is there a mechanical switch in the injector circuit - there is in my system and it is close to the battery which is under the instrument panel. The 10 amp fuse is at the battery. Ideally a redundant engine control system would be powered by its own power source with no shared wiring. To understand where I am coming from, understand that the so called "redundant" electronic engine systems that I've examined do not come close to true redundancy. Most do not have dual injectors and most share a single feed to the injectors. Ken Robert L. Nuckolls, III wrote: > > > At 01:31 AM 4/24/2010, you wrote: >> >> >> In an attempt to keep redundant critical items from the same bus, I >> have placed the fuse (10-15 amp) for my EFI injectors on the Bat Bus. >> However, this violates BoB N's limit of > > Then you need a "mini-contactor" at the battery > bus as illustrated in Z-32, except that the > feeder is for the EFI instead of the E-bus. > > It would be nice if it were a solid state > relay. I believe Eric Jones still offers > on. > > Bob . . . > ________________________________ Message 5 _____________________________________ Time: 08:27:13 AM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Proper SWR meter >When you 'rented' the MFJ259, did you include a simplified instruction sheet? > >As a proud owner of a MFJ259, I would like a 'cook book' type >instructions tailored to the OBAM aviation community. > >I would like to know all the theory etc but at this time do not have >the time to invest in learning its complete capability and retaining >it. I am interested but short on time. My Grandson currently has priority! > >I just want to know how to correctly connect it and read the >SWR. Then some clues as to how to correct it if necessary. As a matter of fact, I think I did but it's on the computer in M.L. I'll see if I can did it up and post it early next week. If not, I'll write up a new one. It's pretty straight forward . . . perhaps a cognizant user of such devices will come up with a procedure before I get to it. Bob . . . ________________________________ Message 6 _____________________________________ Time: 09:07:55 AM PST US Subject: AeroElectric-List: Re: Big load on BAT BUS From: "jonlaury" nuckolls.bob(at)aeroelect wrote: > At 01:38 AM 4/24/2010, you wrote: > > > > > > > Never mind about the SS sleeve question. It will only be a 10 gauge > > wire and I will 18 ga fuselink it at the battery. > > > > > > This sounds like another "loose cannon" > implementation of fusible links. > Bob . . . Admittedly, it is. And that is why I "disclosed" what I was going to do. It seemed like a good idea. The feedback here is invaluable as is an occasional slap upside the head :-) Read this topic online here: http://forums.matronics.com/viewtopic.php?p=295553#295553 ________________________________ Message 7 _____________________________________ Time: 11:18:22 AM PST US From: "J. Mcculley" Subject: Re: AeroElectric-List: Surface temperature sensor Using a laboratory quality temperature instrument I determined the readings (at about 10 degree F intervals) of a typical digital display meat thermometer (10-15 dollar variety some 10 years ago) and found the error varied well within +/- 3F within the range of interest I considered appropriate as about 70 to 300F for firewall-forward applications. Then by carefully extracting the sensor inside the very tip of the meat thermometer, I compared it in size and appearance to a variety of commercially available thermistors and tested several by electrically substituting them in place of the original until finding the one I mentioned by source and part number to be apparently identical in performance over the same range of temperature interest. After completing the installation in the aircraft, another test with the lab-quality meter for comparison gave the same ballpark results and also showed that with the nominal 100K resistance value stated for the thermistor, the total impedance of the completed installation for any likely difference in length of wiring between the closest versus greatest distance of sensors created no error even when wired with the smallest gauge wire I felt appropriate for use in an aircraft installation with heat and vibration considerations. My assumption was/is that the surface mounted electronic circuitry in the meat thermometer display head performs the necessary compensation for non linear characteristics of the basic thermistor. Although I was unable to obtain any data from the thermometer vendor, I assume I was just lucky enough to perhaps have stumbled upon the exact same-source thermistor used in the retail unit. Jim McCulley ======================================================================================== Robert L. Nuckolls, III wrote: > > > At 09:38 PM 4/23/2010, you wrote: >> >> >> Sorry Steve and others...I just thought this subject might be of >> interest to so few that I should not take up bandwith that those not >> interested would have to deal with. But, here it is: >> >> >> This is a very accurate system that I tested with a laboratory quality >> temperature meter and found the accuracy of all my sensors to be two >> degrees F. It may not be very sophisticated, but it is super-inexpensive >> and has never malfunctioned. I use it on every flight to assure myself >> that no changes suddenly occur that could indicate a malfunction. >> >> Mine is about a $15 to $25 system that I've operated now for over seven >> years and upwards of 600 flight hours on it's original internal >> watch-size battery. The sensors are standard mini glass-encapsulated >> thermistors available from most electronic supply sources. I used >> Digi-Key # KC013-ND, 100k ohm units. > > How was it that you determined that the 100K devices were > appropriate to your particular display? Folks should understand > that there are hundreds of remote temperature measurement > products on the market. I've see them use thermocouples, solid > state LINEAR temperature sensors, diodes, the junctions of > transistors (also a diode) AND thermistors. > > http://www.gesensing.com/products/resources/datasheets/ge1.pdf > > Thermistors are inexpensive AND rugged but they have the > distinct disadvantage of being non-linear. So the accurate > temperature display not only needs to know what the resistance > of the device is at say 25C, the designer will compensate for > the shape of temperature/resistance curve as well. > > The first thing one needs to do when adapting a commercial > off the shelf (COTS) indicator to their airplane is to determine > the sensor technology. If a thermistor, then you need to get > the 25C resistance rating, and then the resistance at some > other handy value (boiling water - 100C) and then find > substitute sensors of identical characteristics. > > The really cool thing about the linear, solid state sensors > is that they are direct reading, linear, and of known accuracy > out of the box. I'm not discouraging anyone from exploring > adaptation of any COTS temperature display but understand that > there are some inviolate rules by which the sensing technology > is identified and then duplicated so that the display performs > as expected. > > Bob . . . > > > > > > ________________________________ Message 8 _____________________________________ Time: 12:10:27 PM PST US From: "earl_schroeder@juno.com" Subject: Re: AeroElectric-List: Proper SWR meter I wrote: >When you 'rented' the MFJ259, did you include a simplified instruction sheet? Bob wrote: I'll see if I can did it up and post it early next week. If not, I'll write up a new one. My response: Thanks very much! I'll be watching for it from you or anyone.. Earl Do not Archive. ________________________________ Message 9 _____________________________________ Time: 02:45:09 PM PST US From: Mike Welch Subject: RE: AeroElectric-List: RE: Designing a circuit question > I'm fiddling with a variant of the circuit I > published to convert it to a solid state breaker > instead of current limiter. > I'll see if I can publish that variant tomorro evening. > > Bob . . . Hi Bob=2C If you are still working on this solid state design you talked about=2C I was wondering if it would be possible to incorporate a feature that allows the user to set for different loads. In other words=2C a 2amp setting=2C a 3 amp setting=2C etc=2C etc........ ..or did you intend on this=2C anyway? I'm really looking forward to what you come up with. I definitely plan o n building it!! Mike Welch Do Not Archive _________________________________________________________________ The New Busy is not the old busy. Search=2C chat and e-mail from your inbox .. http://www.windowslive.com/campaign/thenewbusy?ocid=PID28326::T:WLMTAGL:O N:WL:en-US:WM_HMP:042010_3 ________________________________ Message 10 ____________________________________ Time: 07:31:03 PM PST US From: "Valin & Allyson Thorn" Subject: AeroElectric-List: Z-12 Power Grid Behavior Hello Bob K. and anyone else who wants to weigh in. Could I please get confirmation that I'm interpreting the Z-12 power grid design behavior correctly (Z-12 = Main Alt, Standby Alt, One Battery, Main Bus, E-Bus) represented in these statements below? . One can normally fly with E-Bus feed switch ON since an alternator energized Main Bus is at a higher voltage than the battery and it will feed the E-Bus thru the diode when operating. So even if both alternators fail and battery contactor failed the E-Bus will receive battery power without any action required from the pilot. . If the Battery Contactor Relay is opened, isolating the battery from the Main Bus, while either alternator is operating, the alternator will continue to provide good power to the Main Bus and E-Bus without the battery in the circuit. Are these interpretations correct? In the bullet two scenario where the engine is running, an alternator is making power, and the battery contactor relay is open, will there be any power quality or stability issues with the electrical system without the battery in the circuit? Thanks, Valin ________________________________ Message 11 ____________________________________ Time: 07:31:03 PM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Surface temperature sensor >Then by carefully extracting the sensor inside the very tip of the >meat thermometer, I compared it in size and appearance to a variety >of commercially available thermistors and tested several by >electrically substituting them in place of the original until >finding the one I mentioned by source and part number to be >apparently identical in performance over the same range of >temperature interest. Aha! Then there was a rational exercise to pick a thermistor that matched the operating characteristics of the device being cloned. This is the point that we needed to make clear to our readers. There are thousands of thermistor parts of which only a few will directly replace the sensor used in a randomly selected off the shelf thermometer. I assume I was just lucky enough to perhaps have stumbled upon the exact same-source thermistor used in the retail unit. Don't know about 'luck'. You can measure the 25C resistance point for device under study. You could also measure it's resistance at say, two other points over the range of interest . . . like 0C (ice point) and 100C (boiling point). Then by studying the temperature/resistance transfer curves (or as you did, experimentation) you can find a match. Afterr that, you're home free. As you've described, you can switch as many remote sensors in to the display as you like. The only thing I wanted to make clear was that unlike thermocouples and factory calibrated temperature sensors, thermistors are a breed unto themselves. The successful user will have to learn a few dditions to their back of electro-whizzy tricks. Thanks for sharing your experience in this discussion! Bob . . . ________________________________ Message 12 ____________________________________ Time: 07:36:42 PM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Re: Big load on BAT BUS > > This sounds like another "loose cannon" > > implementation of fusible links. > > Bob . . . > > >Admittedly, it is. And that is why I "disclosed" what I was going to >do. It seemed like a good idea. The feedback here is invaluable as >is an occasional slap upside the head :-) Naw, just a short "time out" in "now you know better corner". Folks on this List strive to be gentle but clear teachers. This should be an experience of discovery not of discomfort. Thanks for sharing. 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