---------------------------------------------------------- AeroElectric-List Digest Archive --- Total Messages Posted Sun 05/30/10: 4 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 06:00 AM - Re: D-subminiature Connectors (James Kilford) 2. 06:01 AM - Re: Gauge wiring best practice (James Kilford) 3. 11:23 AM - Re: IVO Prop Electronic CB report (Robert L. Nuckolls, III) 4. 06:57 PM - Re: IVO Prop Electronic CB report (Dennis & Anne Glaeser) ________________________________ Message 1 _____________________________________ Time: 06:00:33 AM PST US Subject: Re: AeroElectric-List: D-subminiature Connectors From: James Kilford Nice one, thank you. That's excellent & timely advice. James On Sat, May 29, 2010 at 12:49 PM, wrote: > > 5/29/2010 > > Hello Fellow Builders, Here is what we are writing about: > > http://en.wikipedia.org/wiki/D-subminiature > > Bob Nuckolls writes: "It's a fact that the majority of d-sub connectors come > with > short, slotted-head 4-40 jack screws that are EXCEEDINGLY > difficult to work with in confined spaces traversed by wire > bundles." ..and ... "the inconvenience of stock, slot-head jack-screws." > > {RESPONSE} He offers a screw handling solution here: > > http://tinyurl.com/34nrdd5 > > I'd like to offer another solution -- use #4-40 machine screws with hex > socket (Allen wrench) drive heads. The hex socket drive head allows one to > manuever the small screws in a manner vastly superior to a straight slot or > phillips drive head screw. > > See here for a source of such screws: > > http://www.microfasteners.com/catalog/products/SSC.cfm > > Here is just one source of tools for handling these screws: > > http://www.bondhus.com/ > > Conventional Allen wrenches work fine for most handling of these screws, but > these Prohold tools will give even more control if needed: > > http://www.bondhus.com/features/prohold/body-0.htm > > 'OC' Says: "The best investment we can make is the effort to gather and > understand knowledge." > > PS: An aerospace vehicle with hex socket or Torx / six lobe / star drive > fasteners is much easier to work on than a vehicle with straight slot or > Phillips drive fasteners. See here for some handy tool kits to work with the > hex socket or Torx / six lobe / star drive fasteners: > > http://www.chapmanmfg.com/ > > ======================================================= > > Time: 10:28:24 AM PST US > From: "Robert L. Nuckolls, III" > Subject: Re: AeroElectric-List: Gauge wiring best practice > > > I would like to make the panel easily disconnectable, and I'm going to > be using something like Tyco AMP MATE-N-LOK connectors for connecting > other things to the panel. (These are multi-way locking connectors, > with crimped pins, supporting various wire gauges -- 10-30AWG at > least). > > Keep in mind that every connector interface adds three new > joints to every wire. Running lots of electro-goodies through a > single connector adds a single point of failure for all > those electro-goodies........ > > BIG SKIP > > > Probably no functional differences. However, it's > been my observation over the years that spending a lot > of time adding complexity for some perceived future > convenience has a poor return on investment. Suggest > you 'enhance' the stock jack-screws and wire each > instrument as a stand-alone system while minimizing > features shared with other systems. > > Bob . . . > > ________________________________ Message 2 _____________________________________ Time: 06:01:04 AM PST US Subject: Re: AeroElectric-List: Gauge wiring best practice From: James Kilford Bob, Thanks for the insights. Perhaps with some smallish changes to the panel, to make it easily removable, it will become easier to implement a fewer-connections electrical installation. The standard DB9s _are_ a pain, but your suggestions, and the others', are definitely going to make life easier... James On Fri, May 28, 2010 at 6:29 PM, Robert L. Nuckolls, III wrote: > > > I would like to make the panel easily disconnectable, and I'm going to > be using something like Tyco AMP MATE-N-LOK connectors for connecting > other things to the panel. (These are multi-way locking connectors, > with crimped pins, supporting various wire gauges -- 10-30AWG at > least). > > Keep in mind that every connector interface adds three new > joints to every wire. Running lots of electro-goodies through a > single connector adds a single point of failure for all > those electro-goodies. > > To connect the UMA instruments, I figure I can go one of two ways: > > 1) wire each UMA-supplied DB9 connector straight through to the power > bus, ground bus, and sender. The downside is that I'd have to screw / > unscrew many connectors to disconnect the 8 or so UMA instruments, > which might be quick tricky behind the panel. > > 2) wire all the DB9 connectors to a multi-way MATE-N-LOK plug behind > the panel, and then wire a MATE-N-LOK socket to the various sensors > and whatnot. This would give me the big advantage of being able to > disconnect all engine instruments in one connector. > > I don't see any downside to this, but any input would be greatly > appreciated. > > You can do this . . . but you'll never find it done > on production aircraft either commercial or military. > It's a little-value-added activity that does add > significant cost-of-ownership and reduces reliability. > > You can replace the stock jack-screws with devices > having extended handles designed for access with > the bare fingers. > > It's a fact that the majority of d-sub connectors come with > short, slotted-head 4-40 jack screws that are EXCEEDINGLY > difficult to work with in confined spaces traversed by wire > bundles. Theres a host of fingers-only, d-sub retention > systems including Positronics V-series and mil-spec slide > locks. There's also a handy but seldom offered wire-bale- > and-clip that used to be VERY popular on printer connectors. > These are easy to incorporate into new products were you want > to order thousands . . . but unfortunately, they're not > often found as catalog items. > > The computer world has offered a variety of extended jack-screw > handles, most of which can be operated with the bare fingers. > My personal choice is the DIY extended jackscrew fabricated > from a piece of 4-40 screw and 3/16" hex threaded spacer. > See: > > http://tinyurl.com/34nrdd5 > > When accessed with the nifty miniature nut-driver from > Xcelite (or similar) one can get a better feel of just > how tight the screw is when replacing it . . . and > it's a light-year away from the inconvenience of > stock, slot-head jack-screws. > > Secondly, I note that each of the instruments requires a 12V supply > and a ground. Can all these engine instruments be connected together > at the instrument panel and then run to the power bus and ground bus > in two "big" wires, or should I run two separate wires back for each > instrument? > > Failure-tolerant design suggests that every electro-whizzie > be treated as a separate system . . . i.e. no single failure > affects more than one system. Just how much your personal > design goals tolerate risks for merging systems is up to > you. What you propose will FUNCTION as expected as long > as everything is working right. > > Also, I've read what it says about grounding, etc., in the > AeroElectric Connection, and the possibility for errors because of > resistance through different ground paths. However, I find that the > UMA instruments have in general four connections: +12V, GND, sensor > +ve, sensor -ve, all connected via a DB-9 socket. Does this mean that > the sensor input has a sort of privileged design because it has its > own ground going direct the instrument? The two grounds could be > connected internally I guess, but I can't work out what difference > that would make! > > Probably no functional differences. However, it's > been my observation over the years that spending a lot > of time adding complexity for some perceived future > convenience has a poor return on investment. Suggest > you 'enhance' the stock jack-screws and wire each > instrument as a stand-alone system while minimizing > features shared with other systems. > > Bob . . . > ________________________________ Message 3 _____________________________________ Time: 11:23:56 AM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: IVO Prop Electronic CB report At 07:43 PM 5/29/2010, you wrote: Bob, I built the 'Prop Pitch Current Limiter and Electronic CB' circuit last week and tested it today. It works as expected, with one minor difficulty - the Amber LED doesn't come on! It flashes briefly when the switch is released, but that's it. The Green LED is lit when the motor is in operation, and the CB feature works great - the motor stops when the current is a bit over 9 amps. The IRFP3703 barely gets warm, but the 0.2 ohm resister does get warm (not too hot to touch - didn't measure). What would cause the Amber LED to not come on? Could I have installed it backwards? (I double checked, but Murphy's Law has not been repealed) One of my EAA Chapter buddies has an O-scope I can borrow, so what (and how) to check? The amber light will illuminate only while the circuit is POWERED UP and in a current limited mode. This is when the voltage across the source shunts of Q114 exceed the Vbe drop of Q115. Q115 collector goes low and does two things: (1) it deprives Q114 of gate drive thus limiting total motor current to some value that provides one Vbe drop of voltage across the source shunts. This is where current limiting happens. During this time, Q115 is in a linear mode of operation. (2) Q115 also pulls down on the base of Q103 which should switch it on "hard" . . . i.e. collector rises very close to level of applied voltage. This causes C112 to charge through R106 until the voltage reaches the magnitude of zener conduction. When the zener starts to conduct, it pulls up firmly (through 1K and zener) on the base of Q115 which should turn it on hard (switch mode) and deprive Q114 of ALL gate drive, thus shutting the motor OFF. As long as power remains applied, Q103 and Q115 should remain turned on hard (Q103 collector near applied votlage, Q115 collector near ground) and the amber LED should be illuminated and the motor should remain un-powered. As soon as you release the switch, the Q115/Q103 "latch" should release. The capacitor discharges through R106, a forward biased collector-base junction of Q103, R104 and R119. The prepares the circuit for the next operating cycle. A voltmeter or scope reading at collector of Q103 should show a very low voltage (under 1 volt) while the motor is running mid stroke. When the stroke limit is reached, the voltage should jump to approximately applied voltage and remain there after the motor shuts down with the prop pitch switch still held. During this time, the amber LED should be lit. If you trigger the 'scope on the rising edge of the voltage at collector of Q103 and use the other channel to watch the gate drive to Q114, gate drive should go away 100-200 milliseconds after Q103 collector goes high. Bob . . . ________________________________ Message 4 _____________________________________ Time: 06:57:37 PM PST US From: "Dennis & Anne Glaeser" Subject: AeroElectric-List: RE: IVO Prop Electronic CB report I discovered a wiring error in my circuit. Hopefully tomorrow I can fix it and re-test. 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