AeroElectric-List Digest Archive

Wed 08/24/11


Total Messages Posted: 9



Today's Message Index:
----------------------
 
     1. 12:49 AM - Re: Power Supply Connections (JOHN TIPTON)
     2. 03:41 AM - Re: cooling fan thermostat (bob noffs)
     3. 06:27 AM - Re: GRT GPS options (rvtach)
     4. 06:46 AM - Battery terminal corrosion (Robert L. Nuckolls, III)
     5. 07:04 AM - Re: Re: GRT GPS options (Tim Olson)
     6. 07:54 AM - Re: GRT GPS options (rvtach)
     7. 11:03 AM - Re: Re: GRT GPS options (David E. Nelson)
     8. 03:34 PM - Re: cooling fan thermostat (user9253)
     9. 06:48 PM - Re: Circuit protection for DO-160 compliance.... (Robert L. Nuckolls, III)
 
 
 


Message 1


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    Time: 12:49:22 AM PST US
    From: "JOHN TIPTON" <jmtipton@btopenworld.com>
    Subject: Re: Power Supply Connections
    Should any such power supply to the aircraft, or indeed any bench testing of equipment, have the battery connected John ----- Original Message ----- From: Robert L. Nuckolls, III To: aeroelectric-list@matronics.com Sent: Tuesday, August 23, 2011 3:44 PM Subject: Re: AeroElectric-List: Power Supply Connections At 03:43 PM 8/22/2011, you wrote: I just bought this power supply for my hangar: http://www.ebay.com/itm/ws/eBayISAPI.dll?ViewItem&item=250852141183&ssP ageName=ADME:L:OU:US:1123 I will plug it into my airplane's electrical system whenever I'm in the hangar and running the instrument panel, such as when updating the navigation database or running the "glass cockpit" in simulator mode for practice. I'll also use it occasionally to top off the battery. I'll plug it into a 120VAC wall outlet and it will supply 12VDC (as adjustable from 10.8 to 13.2 VDC). The availability of capable switch-mode power supplies on eBay has really expanded over the past few years. The $value$ has climbed steadily too. For a short period of time about 7 years ago, the 'Connection offered a 25A, 13.8v power supply for $125 . . . a good value at the time but now one can acquire more output for less dollars. A good example can be seen here: http://tinyurl.com/3kx6rvc These are not necessarily plug-in-play devices for powering up your airplane on the ground . . . but they're close. Some products caution against using them to 'charge a battery'. It's not because the supply might be damaged by such a task, it has to do with the BACKFLOW of current into a power supply that is deprived of AC mains power while still connected to the battery. I have a couple of exemplar supplies on my bench going into a project for a customer. These are 28v, 15A supplies and I'm using them to charge small batteries. Reverse current into a powered down supply is about 50 milliamps. This backflow would ultimately discharge a battery. Also, without a schematic to study, I'm not 100% sure that this backflow would not damage the power supply. I'm wiring Schottky diodes in series with the supplies to prevent this condition. Keep in mind to that a "12-volt" power supply will run your ship's accessories, it takes at least 14.0 volts to top off a battery. Adding 0.5 volts of drop in the isolation diode and you'll find that your supply needs to be rated for 14.5 volts of output. One might consider a relay in series with the supply's output that is powered from the same 120vac source that energizes the power supply. If power is removed . . . or fails while you're not around to deal with it . . . the relay will drop out and effect an automatic disconnect. A relay would be a good companion to the power supply linked above . . . a diode would work well with a power supply rated at 15 volts. In fact, the power supply cited above can be adjusted to offset the small voltage across a heat-sink mounted diode. At 36 Amps, $67 and free shipping, this device is an exceptional value. Bob . . .


    Message 2


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    Time: 03:41:07 AM PST US
    Subject: Re: cooling fan thermostat
    From: bob noffs <icubob@gmail.com>
    i would think mcmaster-carr type places have inline thermostats for this. i have a thermostat off a woodburning stove that is wired inline to a motor that is controlled to go on and circulate air around the stove when the temp. goes up. same deal. i guess i would also look at a panel switch . just turn it on whenever you aren't wearing mittens. those fans use very little current and last ''forever''. bob noffs not elegant but not clunky either unless you leave the thermostat on the stove! On Tue, Aug 23, 2011 at 7:55 PM, Dan Ballin <dballin@gmail.com> wrote: > > Anyone have an easy/elegant solution. I'd like to put a cooling fan > on my glare shield that exhausts the avionics when the temperature > gets over about 120. I figured some use of a thermistor, but need > some guidance. I already have an avionics fan, but in the Legacy at > least, it is nice to be able to exhaust hot air as well, but really > only want it on when needed. > > Thanks > Dan Ballin > Legacy N386DM > >


    Message 3


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    Time: 06:27:51 AM PST US
    Subject: Re: GRT GPS options
    From: "rvtach" <rvtach@msn.com>
    Nelson- The 4.8 volts is for fuel probes but it sounds like a number of other GRT/RV guys have successfully used that output to power the GPS receiver. I will probably go with the converter anyway. Thanks for the detailed explanation of serial/USB/RS-232. As to the PS/2 cable on the GPS I think you are right about that choice of plug being simply convenience. The tech guy at USGlobalSat (and their literature) said that the data output of this GPS is RS-232. After I double check that the GRT will be able to accept what this GPS has to offer (4800 etc), I think that I'll be getting one of these and the 12V -> 5V converter (which will actually convert anything from 10 - 32 volts down to 5 V). I'll need to cut the plug off the GPS cable to get at the data and power wires and build my own connector from a DB9. Can't thank you enough for taking the time to educate me on all this. The best thing about building a plane has been all the people who want to help. Maybe some day I'll have a chance to pay it forward. -------- Jim McChesney Tucson, AZ RV-7A Finishing Kit Read this topic online here: http://forums.matronics.com/viewtopic.php?p=350417#350417


    Message 4


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    Time: 06:46:05 AM PST US
    From: "Robert L. Nuckolls, III" <nuckolls.bob@aeroelectric.com>
    Subject: Battery terminal corrosion
    At 08:28 PM 8/23/2011, you wrote: >Evenin=92 Bob ' > >What causes the terminal posts on a battery to >corrode, and is there any way to stop / prevent it? > It's difficult to get a liquid tight seal between a battery post and the case material on the older style, top-post batteries. Side post batteries seem to be much better but I don't understand why. I;m sure it's a design issue. There have been remedies to the effects of this leakage but no way to stop it. Here's a bit I gleaned from the 'net . . . To prevent corrosion of cables on top post batteries use a small bead of silicone sealer at the base of the post and place a felt battery washer over it. Coat the washer with high temperature grease or petroleum jelly (Vaseline), then place cable on the post and tighten. Coat the exposed cable end with the grease. Most folks don't know that just the gases from the battery condensing on metal parts cause most corrosion. Emacs! Automotive parts stores offer these treated felt washers you can place under a terminal on a top-post battery that contains an alkaline agent which will tend to hold off corrosion. But they will get 'used up' and need to be replaced periodically. Periodic baking soda wash, wire brush brightening and re-assembly followed by coating of grease is probably the easiest but time consuming prophylactic. If you're getting corrosion on a modern, SLVA battery, it's probably suffering from design flaws of some kind. 'Sealed' means SEALED. Bob . . .


    Message 5


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    Time: 07:04:17 AM PST US
    From: Tim Olson <Tim@MyRV10.com>
    Subject: Re: GRT GPS options
    Jim, I used the BR-305 recently to interface with my ELT and my APRS. http://www.myrv10.com/N104CD/upgrades/20110506 To power it, I just used a simple 3-pin regulator with a couple of minor components, potted into epoxy, so it takes the 14V aircraft source and makes it 5V. It's a couple bucks to build your own converter. Personally, although the GPS works great, I wouldn't consider it appropriate for EFIS use in that I think if you're going to drive an EFIS you should strive to use higher quality components, but I am an IFR flier. If you're VFR only and aren't as worried about reliability, then I guess you can go cheap. I figured this one (under $50) was good enough to feed my ELT, and since I can verify it's working properly with my APRS tracking, it turned out pretty good. Tim Olson - RV-10 N104CD do not archive On 8/24/2011 8:24 AM, rvtach wrote: > --> AeroElectric-List message posted by: "rvtach"<rvtach@msn.com> > > Nelson- > > The 4.8 volts is for fuel probes but it sounds like a number of other > GRT/RV guys have successfully used that output to power the GPS > receiver. I will probably go with the converter anyway. > > Thanks for the detailed explanation of serial/USB/RS-232. As to the > PS/2 cable on the GPS I think you are right about that choice of plug > being simply convenience. The tech guy at USGlobalSat (and their > literature) said that the data output of this GPS is RS-232. > > After I double check that the GRT will be able to accept what this > GPS has to offer (4800 etc), I think that I'll be getting one of > these and the 12V -> 5V converter (which will actually convert > anything from 10 - 32 volts down to 5 V). I'll need to cut the plug > off the GPS cable to get at the data and power wires and build my own > connector from a DB9. > > Can't thank you enough for taking the time to educate me on all this. > The best thing about building a plane has been all the people who > want to help. Maybe some day I'll have a chance to pay it forward. > > -------- Jim McChesney Tucson, AZ RV-7A Finishing Kit > > > Read this topic online here: > > http://forums.matronics.com/viewtopic.php?p=350417#350417 > >


    Message 6


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    Time: 07:54:06 AM PST US
    Subject: Re: GRT GPS options
    From: "rvtach" <rvtach@msn.com>
    Tim- Good advice and I agree wholeheartedly with your recommendation for a better GPS for flying in the clouds. I will be VFR only for a while with plans to upgrade to an IFR panel with the addition of a second EFIS and a Garmin 430/530 once I am able to save the funds to accomplish that. -------- Jim McChesney Tucson, AZ RV-7A Finishing Kit Read this topic online here: http://forums.matronics.com/viewtopic.php?p=350436#350436


    Message 7


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    Time: 11:03:40 AM PST US
    From: "David E. Nelson" <david.nelson@pobox.com>
    Subject: Re: GRT GPS options
    Hi John, Sounds like you've got it figured out. Holler if you've other questions. /\/elson On Wed, 24 Aug 2011, rvtach wrote: > > Nelson- > > The 4.8 volts is for fuel probes but it sounds like a number of other GRT/RV guys have successfully used that output to power the GPS receiver. I will probably go with the converter anyway. > > Thanks for the detailed explanation of serial/USB/RS-232. As to the PS/2 cable on the GPS I think you are right about that choice of plug being simply convenience. The tech guy at USGlobalSat (and their literature) said that the data output of this GPS is RS-232. > > After I double check that the GRT will be able to accept what this GPS has to offer (4800 etc), I think that I'll be getting one of these and the 12V -> 5V converter (which will actually convert anything from 10 - 32 volts down to 5 V). I'll need to cut the plug off the GPS cable to get at the data and power wires and build my own connector from a DB9. > > Can't thank you enough for taking the time to educate me on all this. The best thing about building a plane has been all the people who want to help. Maybe some day I'll have a chance to pay it forward. > > -------- > Jim McChesney > Tucson, AZ > RV-7A Finishing Kit > > > Read this topic online here: > > http://forums.matronics.com/viewtopic.php?p=350417#350417 > >


    Message 8


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    Time: 03:34:42 PM PST US
    Subject: Re: cooling fan thermostat
    From: "user9253" <fran4sew@banyanol.com>
    > Anyone have an easy/elegant solution. I'd like to put a cooling fan > on my glare shield that exhausts the avionics when the temperature > gets over about 120 The easiest and cheapest and lightest solution is to run the fan continuously. Avionics last longer when operating cool. If you like to make electronic circuits, here is an elegant solution: http://ww1.microchip.com/downloads/en/DeviceDoc/21448c.pdf The data sheet has a schematic. The IC is available here: http://www.mouser.com/ProductDetail/Microchip/TC648VPA/?qs=JaP0%252bruNJH%2f4ckdZw9AR1g%3d%3d The TC648VPA can be set to maintain any desired temperature. Joe Gores -------- Joe Gores Read this topic online here: http://forums.matronics.com/viewtopic.php?p=350495#350495


    Message 9


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    Time: 06:48:59 PM PST US
    From: "Robert L. Nuckolls, III" <nuckolls.bob@aeroelectric.com>
    Subject: Re: Circuit protection for DO-160 compliance....
    > > >Are there any suggestions for signal and power filtering (resistor, >cap, etc.) so that my little comparitor and LED drive circuit is as >robust as something designed for DO-160 compliance? I'm skilled >enough to make some good guesses but if there are any tried true >(aircraft/ DO-160) methods for protecting the low impedance (power) >input and the high impedance (comparitor) inputs I'd love to hear >about them. (I don't need best guesses or untried approaches as >I've got plenty of those already). It's somewhat circuit dependent. Sketch out your circuits with component values and mail them to me. I'll sketch suggested protection/ conditioning onto your drawings and return them. Once your project is meeting design goals, I'd be pleased if you share details with the List . . . Bob . . .




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