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#31
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Jay Honeck wrote:
Personally, I think the dimmer circuitry in the Cherokee is perhaps the dumbest thing I've seen in aviation. Even I, as a total neophyte, can see that the system is hopelessly obtuse. Ray has explained to you, twice in this thread, why transistors are used. If you can't understand the technology, stop commenting on it. --- Jay -- __!__ Jay and Teresa Masino ___(_)___ http://www2.ari.net/jmasino ! ! ! http://www.oceancityairport.com http://www.oc-adolfos.com |
#32
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Roy Smith wrote:
Ray Andraka wrote: When my dimmer does go, or I add more lighting to the panel, I'll probably opt for one of the pulse width modulated ones (those are much more complicated than the piper pass transistor, but they also dissipate very little power). The next step in the evolution is to get rid of all those incandescant bulbs and replace them with LEDs. Lower power consumption for the same light output, and they never burn out. Yep.., I've made my own GE330 replacements for the annuniciator and gear-down lights using white LEDs. I believe there are commercially avialable units but be carefull because incandescent lamps are non-polarised but the polarity of the lamp sockets is random. (My Arrow requires a + base for the gear lamps but a - base for the annunciators) |
#33
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-And any engineer that designs a dimming circuit without short circuit
protection of the output device should be staked out with ants and honey. Yes, I agree, however it wasn't designed with output protection and anybody that works on it shoud understand that - I have my sources that I've published with a Chief Counsel's opinion. A chief counsel doesn't survail those of us out in the field. As -the chief inspector for a large repair station, if I see an aircraft for an -annual with some kind of aftermarket or home made dimmer system....it better -have a 337 associated with it....not because I'm a jerk or an a**hole, but -because that is what the regulations require. -And again, I beg to differ with your interpretation, as does the Chief Counsel. I beg to differ with you and your chief counsel's opinion, if its not as it came from the factory then it does not conform to its type design and needs a vehicle of approval, what-ever that may be. I'll be glad to argue that point to you or counsel (as long as we can avoid the flaming) - Them's the breaks, ain't they? Yup, its a heck of a biz....gotta love it or it'll kill ya....figuratively - Ask your FAA inspector for the approved definition of safety. There is none. How can any agency guide toward that which it can't even define?" Jim, of all the stuff of your's I've read, I must say that is a great line..... Lets not however, miss the forest for the trees. Some legal eagle in a nice air conditioned office hasn't a clue about what really happens out here on the front lines of the maintenance battlefield. Those of us with grease under our finger nails don't deal with a Chief Counsel, we deal with Aviation Safety Inspectors that may or may not know as much as we do. Truth be told, I really enjoy "playing ball" with the FAA, but, ya know.....if I make 'em mad enough, they'll take the ball and bat and go home....if you know what I mean. By the way, I'd enjoy arguing regulations with you....as chief inspector for a repair station, that's what I do for a living. Unfortunately, my responses may be a little delayed if it involves quoting regs. I surf news groups from home and all my reg stuff is at work. I've proven the Feds wrong a few times, but eaten a lot of crow along the way! By the way Jim, didn't I read in one of your posts that you were a Ham?? Be glad to try a sked on HF and we can really get into a spirited discussion.....I can work 160 up to 10 with 100 watts to a dipole oriented east to west. best 73 John |
#34
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Ray has explained to you, twice in this thread, why transistors are used.
If you can't understand the technology, stop commenting on it. Wow, we normally can't find anyone here to defend the high-tech 1974 Chevy Nova technology found in my Piper -- thanks! Your view is, um, refreshing, somehow. Kinda like the Amish, I suppose, but I guess I could get used to it. Actually, flying a 30 year old airplane, I have little choice. :-( -- Jay Honeck Iowa City, IA Pathfinder N56993 www.AlexisParkInn.com "Your Aviation Destination" |
#35
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: Personally, I think the dimmer circuitry in the Cherokee is perhaps the
: dumbest thing I've seen in aviation. Even I, as a total neophyte, can see : that the system is hopelessly obtuse. : Strangely, older Cherokees had a much simpler dimmer circuit. I wonder why : Piper made it so complex later on, and I wonder if they've corrected this : mess in their new planes? I won't debate the older vs. newer circuit too much, except to say that it moves the heat loss from a rheostat to a transistor. Both are linear "regulators", but due to the changing load requirements a resistor makes a very poor choice. My plane's the older variety, and the lights are off for about 75% of the travel of the dimmer. The other 25% goes from off to full bright, and makes the last 25% of the rheostat coils have to dissipate all the power. They're both a bit clunky (PWM being more efficient, but prone to noise as previously mentioned). Aside from this being an AIRPLANE, the transistor setup is CHEAPER and "better" from the linearity and robustness standpoint (TO-3 package 2N3055 is a tough transistor that can dissipate a lot of power). In reality, the 20W or so max is negligible power lost (1-2A draw) and a decent compromise for complexity and noise immunity. Still better are LEDs... less power, and even a linear regulator won't have to dissipate much. Hope that helps describe why they went to it. -Cory -- ************************************************** *********************** * The prime directive of Linux: * * - learn what you don't know, * * - teach what you do. * * (Just my 20 USm$) * ************************************************** *********************** |
#36
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Hope that helps describe why they went to it.
Thanks, Cory! Do you know if there's a legal way to put LEDs in my plane? -- Jay Honeck Iowa City, IA Pathfinder N56993 www.AlexisParkInn.com "Your Aviation Destination" |
#37
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"Jay Honeck" wrote in message news:rkp4c.18266$mM.131800@attbi_s02...
And it's not even for the Dept. of Defense! :-) For those of you thinking about airplane ownership (and I know you're lurking out there!), we just got the bill to replace one of the two dimmer switches (and a few light bulbs) in our Pathfinder's panel. $104 in parts, 5 hours labor (It's a real bitch to diagnose and get at in a Cherokee...). Total: $429.73. Gotta love aviation. That is why alot of us are building experimental planes. I have owned several certified ships and "Never" again will I get screwed......Happy Flying. Ben Haas N801BH |
#38
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On Sat, 13 Mar 2004 08:10:48 -0800, Jim Weir wrote:
Had a double helping of bitch flakes this morning, did we Stu? Jim Man, I just couldn't resist! Stu Gotts shared these priceless pearls of wisdom: -Oh no! Someone having the audacity to disagree with King Weir! -That'll make him spit out his morning latte! Stand by for the flames. Jim Weir (A&P/IA, CFI, & other good alphabet soup) VP Eng RST Pres. Cyberchapter EAA Tech. Counselor http://www.rst-engr.com |
#40
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And please to add: http://www.awp.faa.gov/new/fsdo/ans_jan2_98.htm http://www.awp.faa.gov/new/fsdo/ans_july1_97.htm http://www.awp.faa.gov/new/fsdo/ans_apr3_99.htm Jim shared these priceless pearls of wisdom: -On 13 Mar 2004 22:26:18 GMT, ospam (JohnN3TWN) -wrote: - -snip - -By the way, I'd enjoy arguing regulations with you....as chief inspector for a -repair station, that's what I do for a living. Unfortunately, my responses may -be a little delayed if it involves quoting regs. I surf news groups from home -and all my reg stuff is at work. - -http://www.access.gpo.gov/nara/cfr/w...4cfrv1_04.html - -enjoy - -TC Jim Weir (A&P/IA, CFI, & other good alphabet soup) VP Eng RST Pres. Cyberchapter EAA Tech. Counselor http://www.rst-engr.com |
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