---------------------------------------------------------- AeroElectric-List Digest Archive --- Total Messages Posted Tue 03/18/03: 13 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 05:49 AM - two computers (klehman@albedo.net) 2. 06:03 AM - Oil level switch (Gary Casey) 3. 06:08 AM - one last contactor diode question (Gary Casey) 4. 06:28 AM - Re: Oil level switch (Benford2@aol.com) 5. 08:29 AM - Re: one last contactor diode question (Canyon) 6. 10:30 AM - Re: AeroElectric-List Digest: 29 Msgs - 03/17/03 (MikeM) 7. 10:34 AM - Re: Archer Comm antenna hookup (Julia) 8. 02:07 PM - neat site for 0-Rings (Julia) 9. 02:08 PM - Turn coordinator noise (Shay King) 10. 03:31 PM - Re: Archer Comm antenna hookup (David.vonLinsowe) 11. 09:06 PM - Re: Oil level switch (Finn Lassen) 12. 09:11 PM - Re: RG Batteries at UAP/NAPA (Van Caulart) 13. 09:40 PM - Re: European hole spacing (Tony Babb) ________________________________ Message 1 _____________________________________ Time: 05:49:00 AM PST US From: klehman@albedo.net Subject: AeroElectric-List: two computers --> AeroElectric-List message posted by: klehman@albedo.net This is a very general question and note that my thoughts are the opinion of a builder who has not flown yet. However I'd suggest that high voltage coil joiners can be an excellant solution for the ignition although not really suitable for coil on plugs. Joiners are multiple diode strings that have proven to be very very reliable. If one diode shorts it has no effect. One can always measure the forward voltage drop annually. As long as it does not drop significantly from the 60 volts (approx.) of a new unit, you can be assured that all is well. If one whole diode string shorts, again the engine keeps running. Therefore one can run two otherwise independant ignition units each from its own electrical system (if you are using two electrical systems). Coil joiners get more complex with waste-fire systems since one of each plug pairs operates with reverse polarity, but there are several options. For coil on plugs, I'd consider switching the coil power supply and all the triggers to insure that a shorted driver does not prevent the second system from functioning. Or insure that you can maintain flight with one dead cylinder. Note that a 4 cylinder engine will lose AT LEAST 40% power in an airplane with one dead cylinder due to pumping losses and the other cylinders operating at lower rpm, etc. My own solution for two efi computers is to also feed them from different electrical systems. I then fitted extra injector(s) with a separate filter, fuel rail and regulator for the second system. However the 12 volt feed to the extra injector(s) will normally be switched off (one SPST switch) unless it is required and the primary system is turned off first. To avoid the weight of a third fuel pump it will also require a fuel valve selection to pressurize the second fuel rail on my implementation. Overkill? - probably, but a Megasquirt efi computer is only $110. (check out the web site) and the rest was recycled. Too many auto engine conversions have come out of the sky due to single component failures in ignition and fuel systems. Unlike cars or certified installations built in quantity, these systems are always unique in some aspects and not near as well tested. Without redundancy, unique failure modes will continue to show up, in my opinion. Just last week I heard of a crankshaft sensor failure (in flight) that several people have claimed for years to be as reliable as dirt. It was as reliable as dirt WHEN installed in the factory in a car... Ken > < engines. > I see how you wire two hot busses from 2 batteries to the two computers. > But how do I wire the fuel injectors and the coils to the two separate > batteries? What do you think would work the best? > Thanks, > Leonard>> ________________________________ Message 2 _____________________________________ Time: 06:03:47 AM PST US From: "Gary Casey" Subject: AeroElectric-List: Oil level switch --> AeroElectric-List message posted by: "Gary Casey" < AeroElectric-List message posted by: Finn Lassen If I remember correctly, one side if the switch is already grounded to the oil pan. I put a hi-intensity LED in my panel, connected to +12V on one side via a (470 or 4700 ohm?) resistor and the other side of the LED to the wire from the switch. You could get more fancy: one side of a relay coil to +12V and the other side of the coil to the switch. Then use the relay contacts as you see fit to drive a lamp, audible alarm or whatever.>> Remember that oil level switches in automotive engines are used to check the oil BEFORE starting, not during operation. They are shut off while the engine is running as the oil level will normally drop below the switch level. Even if the switch is mounted low enough to work during operation there is some concern that aeration and turbulence will cause false actuation. If you just wire it to a light, the light may be on all the time the engine is running. Gary Casey ________________________________ Message 3 _____________________________________ Time: 06:08:01 AM PST US From: "Gary Casey" Subject: AeroElectric-List: one last contactor diode question --> AeroElectric-List message posted by: "Gary Casey" <> One last question, honest. I heard once somewhere that the starter contactor will be less "vigorous" in opening the contacts with a diode across it and therefore will be slightly more likely to weld than with no diode. In my Cardinal the ignition switch lasted for 30 years without a diode, but the AD was just complied with which resulted in new contacts AND a diode across the starter contactor. hmm.. Gary Casey ________________________________ Message 4 _____________________________________ Time: 06:28:52 AM PST US From: Benford2@aol.com Subject: Re: AeroElectric-List: Oil level switch --> AeroElectric-List message posted by: Benford2@aol.com In a message dated 3/18/2003 7:04:25 AM Mountain Standard Time, glcasey@adelphia.net writes: > > > Remember that oil level switches in automotive engines are used to check > the > oil BEFORE starting, not during operation. They are shut off while the > engine is running as the oil level will normally drop below the switch > level. Even if the switch is mounted low enough to work during operation > there is some concern that aeration and turbulence will cause false > actuation. If you just wire it to a light, the light may be on all the > time > the engine is running. > > Gary Casey > Very good point. The oil pressure gauge and light is the one thing ya need to keep an eye on. ________________________________ Message 5 _____________________________________ Time: 08:29:11 AM PST US From: Canyon Subject: Re: AeroElectric-List: one last contactor diode question --> AeroElectric-List message posted by: Canyon Gary Casey wrote: >One last question, honest. I heard once somewhere that the starter >contactor will be less "vigorous" in opening the contacts with a diode >across it and therefore will be slightly more likely to weld than with no >diode. In my Cardinal the ignition switch lasted for 30 years without a >diode, but the AD was just complied with which resulted in new >contacts AND >a diode across the starter contactor. hmm.. --- Hi Gary, First, I don't mind questions -- I just figured folks were tired of my 'firm' answers on diode suppression stuff. Second, I'll offer two answers. The simple answer is yes, there will be a very small difference with and without the diode which you would only know about if you made lab condition measurements and is of no practical consequence as the time difference is tiny compared to the time line of the total system characteristics. The longer answer is that starter contactors I'm familiar with will store a little more energy than most smaller relays because they have more inductance. As a consequence they are likely to take longer than the typical smaller relays to open. The extra time with any of these is mostly dependent on the inductance of the coil -- and natural resonances due to the combined effects of internal coil and system distributed reactances of the application. The transient frequency produced will be a function of this resonance factor but the coil will attempt to begin oscillation at its natural frequency and at a peak voltage of L(di/dt) caused by the switch's abrupt opening. Note that system dt is heavily influenced by the distributed reactances of the circuit but driven by the switch's opening speed, which for typical switches is relatively slow compared to semiconductor switches. The energy stored in the coil will be determined by L(i 2/2) and will be dissipated as heat in the diode within essentially the first half cycle of the attempted oscillation of the circuit, quenching switch contact arc before it really gets started good. But without knowing the exact parameters involved with typical starter contactors and switches, it is not possible for me to characterize the time delay exactly. All of these factors can be lab condition measured and results determined definitively. My background is with complex systems for military, commercial and industrial systems so my practical experience doesn't encompass very much purely aviation-typical component experience and I would defer to Bob for estimates of times for this in practice. This list is very fortunate to have Bob here with a vast amount of on target practical experience and real professional background and advice. However, I have spent a LOT of time with similar components and would be very much surprised if he disagreed with my statement that the time delay opening a starter contactor with diode suppression is of no practical consequence. Just make sure the diode suppressors are installed with short leads as close to the coil as is practical. Regards, Steve ________________________________ Message 6 _____________________________________ Time: 10:30:57 AM PST US From: MikeM Subject: AeroElectric-List: Re: AeroElectric-List Digest: 29 Msgs - 03/17/03 --> AeroElectric-List message posted by: MikeM > Subject: AeroElectric-List: Microair comm and Flightcom 403 intercom wiring > > I'm wiring up a Flightcom 403 intercom to my Microair radio. The intercom wiring > diagram seems pretty clear...the only connections it has to the radio are the > PTT, headphone, mic, and avionics ground (shown tied to the same ground point > as the radio). No problems there. Just wondering about the radio wiring though...does > the Mic Ground (also called Mic Lo, pin 2 on the Microair) need to > be tied to ground to make the communication with the intercom work, or can it > just be left unconnected? > > Thanks, > > --Mark Navratil It has been my experience that the pins labelled "Mic Lo" on most radios are just internally tied to the radio's "Power Ground" pin. Take an Ohmmeter, and measure the resistance between Pin2 on the MicroAir, and whatever pin is the MicroAir's Power ground pin. If you read a dead short, then you can consider pin 2 to be just another ground connection on the MicroAir. While you are at it, measure between the MicroAir's case and its Power Ground pin. This still leaves open the question of how to connect the "Mic Out" from the intercom to the "Mic Input" of the MicroAir? If you use a shielded wire, the question is what to do with the shield: 1. connect both ends of the shield; one end to Intercom ground, other end to MicroAir Mic LO. 2. Connect the shield to Intercom ground, leave the MicroAir end open. 3. Connect the shield to MicroAir MicLo, leave the intercom end open. 4. Dont bother shielding the Mic line, i.e. use an unshielded wire. Guess what? In 97% of installations, where the power grounds from all of the individual avionics items are short (less than a few feet), and are terminated at a "common" ground terminal, any of the four methods above will work just fine. The mic line audio level is sufficiently high, and is at a low enough impedance, that even shielding is optional (good practise, but optional). Shielding audio lines usually involves keeping RF from the transmitter out of them, and has little to do with preventing capacitive coupling at audio frequencies. In methods 2 thru 4, you are relying on the fact that both the intercom and MicroAir are already connected together through their respective power grounds. The Mic signal return path is through the power wiring via the common ground point. In method 1, you are slightly lowering the ground path resistance by shunting the preexisting ground path with a direct connection between the two units (thru the shield). Practically, with method 1 you may reduce 20mOhms of ground impedance to 10mOhms... In high-quality audio, data aquisition and instrumentation applications, the SigHi-SigLo nomenclature implies an isolated, differential signal pair which is isolated (optically, transformer, differential instrumentation amplifier) from ground. This is done to break "ground loops", and to prevent "common mode" noise from coupling into the desired signals. However, in avionics I have never seen anything but SigLo just being another "GROUND" pin... If the MicroAir MicLo pin is isolated from ground, then only Method 1 above will work, and my hat is off to MicroAir. Mike Mladejovsky (one Czech to another) Gray haired PhDEE Instrumentation Engineer Skylane '1MM Pacer '00Z ________________________________ Message 7 _____________________________________ Time: 10:34:06 AM PST US From: Julia Subject: Re: AeroElectric-List: Archer Comm antenna hookup --> AeroElectric-List message posted by: Julia I got the following from Bob himself - so I guess I had it backwards incase anyone else is interested. Bob writes: You have it just backwards! The center conductor connects to the the insulated little piece of aluminum which spaced from the main part of the antenna forms a capacitor which feeds the rest of the antenna. This devive is called a "Gamma" match. With this device there are enough antenna parameteres that the antenna can be tuned as perfectly as is possible. Julia wrote:--> AeroElectric-List message posted by: Julia I'm hooking up my bob archer comm antenna -the one for the wing tips - I lost the directions? does this sound right - the center coax cable wire goes to the terminal which connects to most of the metal on the antenna -the other antenna terminal seams to be insulated from the rest of the antenna itself - this secound terminal on the antenna just goes to a smaller section of metal which is insulated from the rest of the antenna - i'm assuming this would be the ground? thanks --------------------------------- --------------------------------- ________________________________ Message 8 _____________________________________ Time: 02:07:50 PM PST US From: Julia Subject: AeroElectric-List: neat site for 0-Rings --> AeroElectric-List message posted by: Julia check out www.allorings.com -neat site for all your o-ring needs --------------------------------- ________________________________ Message 9 _____________________________________ Time: 02:08:48 PM PST US From: "Shay King" Subject: AeroElectric-List: Turn coordinator noise --> AeroElectric-List message posted by: "Shay King" Dear Bob, I've installed a cheap turn coordinator in my CH701. It's causing noise in the headset when intercom on, or when transmitting. No noise when receiving only. I've looked at some of your suggestions in the archive and will try some of them tommorrow. Is it likely that if I had bought an expensive instrument that it wouldn't cause noise problems? Regards, Shay King. ________________________________ Message 10 ____________________________________ Time: 03:31:06 PM PST US Subject: AeroElectric-List: re: Archer Comm antenna hookup From: "David.vonLinsowe" --> AeroElectric-List message posted by: "David.vonLinsowe" I just converted mine to Bob's antenna's. It's the other way around. The center conductor of the coax goes to small section of aluminum. The rest of the antenna is grounded. Also be certain that if you have any lights in the tips that the wires run up the front leg of the antenna. The antennas work great even with the strobes out there flashing away! I picked up 5 1/2 mph on the top end by moving the COM, VOR/GS, marker beacon and transponder antennas out of the breeze Dave RV-6 The need for (more) speed----> Time: 06:46:27 PM PST US From: Julia Subject: AeroElectric-List: Archer Comm antenna hookup --> AeroElectric-List message posted by: Julia I'm hooking up my bob archer comm antenna -the one for the wing tips - I lost the directions? does this sound right - the center coax cable wire goes to the terminal which connects to most of the metal on the antenna -the other antenna terminal seams to be insulated from the rest of the antenna itself - this secound terminal on the antenna just goes to a smaller section of metal which is insulated from the rest of the antenna - i'm assuming this would be the ground? thanks ________________________________ Message 11 ____________________________________ Time: 09:06:17 PM PST US From: Finn Lassen Subject: Re: AeroElectric-List: Oil level switch --> AeroElectric-List message posted by: Finn Lassen Well, that is not the case for the Mazda 13-B rotary. I sure would like to know if I have developed an oil leak while airborne. A sensor that doesn't work that way is worthless in my opinion. Finn Gary Casey wrote: >--> AeroElectric-List message posted by: "Gary Casey" > >< >--> AeroElectric-List message posted by: Finn Lassen > > >If I remember correctly, one side if the switch is already grounded to >the oil pan. >I put a hi-intensity LED in my panel, connected to +12V on one side via >a (470 or 4700 ohm?) resistor and the other side of the LED to the wire >from the switch. > >You could get more fancy: one side of a relay coil to +12V and the other >side of the coil to the switch. >Then use the relay contacts as you see fit to drive a lamp, audible >alarm or whatever.>> > >Remember that oil level switches in automotive engines are used to check the >oil BEFORE starting, not during operation. They are shut off while the >engine is running as the oil level will normally drop below the switch >level. Even if the switch is mounted low enough to work during operation >there is some concern that aeration and turbulence will cause false >actuation. If you just wire it to a light, the light may be on all the time >the engine is running. > >Gary Casey > > ________________________________ Message 12 ____________________________________ Time: 09:11:34 PM PST US From: Van Caulart Subject: AeroElectric-List: Re: RG Batteries at UAP/NAPA --> AeroElectric-List message posted by: Van Caulart FYI I just happened into A UAP/NAPA store the other day looking for the flasher unit to power the landing/taxi light combo and I found that they now carry a complete line of RG Batteries. The line up is marketed to recreational toy like ATV's, jet skies, boats and such. The 18XL is a 300CCA 20ah 18lb beast which measures 12" long 4" wide and 8" in height. The complete "prosport" line is crossed referenced to other RG battery manufacturers. The "good ole boy" (best customer) price was $89Cdn. roughly $60US. When I told my AME about this his eyes just lit up and he said "sounds great stick one in the plane and save the "pink" one for the annual." I love this mechanic. Each time I show him a better way and he's satisfied that it is better, he'll find a legal way to sign it off. BTW the alternating flasher is one used on a school bus and is rated for two sealed beams or a number of bulbs. I'll pick up the flasher unit this week. PeterVC ________________________________ Message 13 ____________________________________ Time: 09:40:00 PM PST US From: "Tony Babb" Subject: Re: AeroElectric-List: European hole spacing --> AeroElectric-List message posted by: "Tony Babb" aaah, been there, done that !!. Publishing hard copy for outside of N & S America can be tricky. Generally you'll see two or four ring binders outside the N & S America using A4 paper and generally you'll see 3 ring binders in the US using 8.5 x 11 paper. I know there are exceptions but generally true. Also, don't forget A4 is a little bit longer and a little bit narrower than 8.5 x 11 so may stick out of the binder. If you print from softcopy you have to watch margins etc. FWIW we ended up designing a page size that was a little bit narrower than 8.5 inches and a little bit shorter than A4 (11 inches) so we knew the contents of each page would be the same no matter what size paper was used. Then printed some on A4 with four holes and some on 8.5 x 11 with three holes. The extra trouble and expense is just not worth it unless you have large volumes of print in mind for both markets.