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
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--> 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
> <<I have a question about wiring the fuel injected and coil over plug
> 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
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| Subject: | Oil level switch |
--> AeroElectric-List message posted by: "Gary Casey" <glcasey@adelphia.net>
<<Subject: Re: AeroElectric-List: GM low oil sensor
--> AeroElectric-List message posted by: Finn Lassen
<finnlassen@netzero.net>
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
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| Subject: | one last contactor diode question |
--> AeroElectric-List message posted by: "Gary Casey" <glcasey@adelphia.net>
<<In truth, the best, most effective and
safest transient suppression is accomplished with a diode placed
immediately across the inductive element - period. All other methods
using resistors, capacitors, varistors, transorbs etc are far inferior
and thus far less desirable. Don't know how these myths get started...
Steve >>
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
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| Subject: | Re: 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
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| Subject: | Re: one last contactor diode question |
--> AeroElectric-List message posted by: Canyon <steve.canyon@verizon.net>
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
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| Subject: | Re: AeroElectric-List Digest: 29 Msgs - 03/17/03 |
--> AeroElectric-List message posted by: MikeM <mladejov@ced.utah.edu>
> 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
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| Subject: | Re: Archer Comm antenna hookup |
--> AeroElectric-List message posted by: Julia <wings97302@yahoo.com>
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 <wings97302@yahoo.com> 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
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| Subject: | neat site for 0-Rings |
--> AeroElectric-List message posted by: Julia <wings97302@yahoo.com>
check out www.allorings.com -neat site for all your o-ring needs
---------------------------------
Message 9
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| Subject: | Turn coordinator noise |
--> AeroElectric-List message posted by: "Shay King" <shaking@eircom.net>
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
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| Subject: | re: Archer Comm antenna hookup |
--> AeroElectric-List message posted by: "David.vonLinsowe" <David.vonLinsowe@delphi.com>
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 <wings97302@yahoo.com>
Subject: AeroElectric-List: Archer Comm antenna hookup
--> AeroElectric-List message posted by: Julia <wings97302@yahoo.com>
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
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| Subject: | Re: Oil level switch |
--> AeroElectric-List message posted by: Finn Lassen <finnlassen@netzero.net>
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" <glcasey@adelphia.net>
>
><<Subject: Re: AeroElectric-List: GM low oil sensor
>
>--> AeroElectric-List message posted by: Finn Lassen
><finnlassen@netzero.net>
>
>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
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| Subject: | Re: RG Batteries at UAP/NAPA |
--> AeroElectric-List message posted by: Van Caulart <etivc@iaw.on.ca>
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
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| Subject: | Re: European hole spacing |
--> AeroElectric-List message posted by: "Tony Babb" <tonybabb@alejandra.net>
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.
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