Today's Message Index:
----------------------
1. 06:42 AM - Re: OVM nuisance trips during engine start (Ken)
2. 07:10 AM - Re: Z-13 Component Locations for RV-7 (Robert L. Nuckolls, III)
3. 12:03 PM - Re: Why use starter contactor? (Robert L. Nuckolls, III)
4. 12:56 PM - intercom ground loop? (Mickey Coggins)
5. 01:45 PM - Re: OVM nuisance trips during engine start (Robert L. Nuckolls, III)
6. 05:19 PM - B&C SD 8 alternator (Chris Hukill)
7. 07:39 PM - Re: power for headsets (James Freeman)
8. 08:00 PM - Re: power for headsets (Alan K. Adamson)
9. 08:28 PM - Re: B&C SD 8 alternator (Hinde, Frank George (Corvallis))
Message 1
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Subject: | Re: OVM nuisance trips during engine start |
--> AeroElectric-List message posted by: Ken <klehman@albedo.net>
Thank you for your thoughts Bob.
I considered adding a diode in series with the 392 R resistor to pull up
the reference voltage quicker but discarded the idea. I was thinking
that while the voltage was rising immediately after cranking, such a
diode would give the trigger voltage a 0.6 volt headstart so to speak.
As you point out though that doesn't matter if the reference voltage
doesn't sag in the first place. Have to check again but I think I'm just
barely seeing over 12 volts at the time that I start cranking so not
much headroom to bring the ref. voltage up to 12 volts before cranking.
Maybe there's a schottky type diode in my junk pile... er..parts bin.
This is an EFI engine so it does not normally need much cranking. I will
try this diode on one of the OVM's this morning but it will take awhile
before I know whether it does the trick.
My analog scope is not the greatest tool for capturing one shot
transients. I've been searching for a low cost portable or laptop DSO
for the last couple of days as I'd also like some proof that my ignition
is not occasionally missing a beat. There are a couple of offerings that
seem like they might be useful in the $200 to $400. range. The
megasquirt backup fuel injection that I'm using has datalog capability
to a laptop and that is opening my eyes a bit to how useful digital
recording can be.
Ken
Robert L. Nuckolls, III wrote:
>--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <nuckollsr@cox.net>
>
>At 12:23 PM 4/3/2006 -0400, you wrote:
>
>
>
>>--> AeroElectric-List message posted by: Ken <klehman@albedo.net>
>>
>>Well now that I also have some hours on the engine and am on record as
>>saying that nuisance OVM trips should not be tolerated, I must report
>>that I am experiencing an OVM crowbar trip about every 10 th start or
>>start attempt. This is a 12 volt Z-14 with small AGM batteries that
>>parallel during cranking. Usually both homebuilt OVM's trip. If they
>>trip it is usually on the first start (or start attempt) of the day and
>>then no more on that day.
>>
>>My theory is that the cranking voltage is sagging way below the 12 volt
>>zener and dragging the reference voltage down faster than it is dragging
>>down the trigger voltage. (The time constant of the trigger circuit is
>>higher than the time constant of the RC reference filter) My first
>>inclination was to just add a lot of capacitance across the zener,
>>especially since I haven't upgraded my 4.7 uF cap there to the 22 uF
>>that is shown on the latest revision. However that would mean that after
>>cranking ceases, the rising voltage would drive up the trigger voltage
>>faster than the reference voltage and again possibly cause a trip. I am
>>planning to try an intermediate experiment with a 68uF cap just for love
>>of an experiment on one of the OVMs.
>>
>>
>
> Ken, thank you for sharing this with us. Another thing to
> consider is putting a diode in series with the 392 ohm
> resistor. This will keep the momentary brown-out spike from
> pulling down on the capacitor during the transient.
>
>
>
>
>>I think the best solution however is to use a lower voltage zener
>>perhaps 8 or 9 volts and adjust the appropriate resistor values. I
>>believe that would tend to make the circuit imune to low 8 or 9 volt
>>cranking voltages and still retain acceptable accurancy. After all the
>>24 volt version uses a 12 volt zener and I suspect it is imune to this
>>type of tripping?? I plan to do that on at least one of my OVM's and
>>will report the results. The engine cranks briskly and has fairly short
>>starter wires. The cranking voltage does drop enough to cause my EIS4000
>>engine monitor to reset however.
>>
>>
>
> Have you ever put a 'scope on it to find out how low it
> goes? It would be interesting to know. Also, since I'm
> phasing out the MBS4991 trigger diode for all future
> production, I have an inventory that I'm going to offer
> for those who would like to fabricate the original circuit
> that was not plagued with the phenomenon you've identified.
>
> In any case, I think your analysis has merit and adding the
> diode would break the pull-down path during brownout time.
>
> Bob . . .
>
>
>
Message 2
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Subject: | Re: Z-13 Component Locations for RV-7 |
--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <nuckollsr@cox.net>
At 08:01 PM 3/27/2006 -0800, you wrote:
>--> AeroElectric-List message posted by: "PIAVIS" <piavis@comcast.net>
>
>I'm starting to figure out where all the components for the Z-13 system get
>located in my RV-7. I'm tempted to have everything except the main current
>limiter and the battery/starter contactors on the hot side of the firewall,
>with everything else on the cold side. Is this how most have installed the
>system?
Not sure what you mean by "everything" . . .
As a general rule, battery contactors mount as close as practical
to batteries. Starter contactors as close as practical to starters.
Place other equipment items so as to minimize the numbers of wires
passing through the firewall.
Bob . . .
< What is so wonderful about scientific truth...is that >
< the authority which determines whether there can be >
< debate or not does not reside in some fraternity of >
< scientists; nor is it divine. The authority rests >
< with experiment. >
< --Lawrence M. Krauss >
Message 3
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Subject: | Re: Why use starter contactor? |
--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <nuckollsr@cox.net>
At 11:18 AM 1/27/2006 -0600, you wrote:
>--> AeroElectric-List message posted by: "Dave Morris \"BigD\""
><BigD@DaveMorris.com>
>
>At 09:59 AM 1/27/2006, you wrote:
> >
> >If you
> >get in a crash and the engine is ripped off, I don't think the battery
> >cable will be you only problem. George
> >
>
>It may not be, but it could mean the difference between walking away doused
>in gasoline, and walking away on fire, hoping somebody can get to you
>quickly enough to put out the flames.
>
>This happened to a friend of mine who would have walked away from a crash
>if it had not been for that one little spark. I'm putting a starter
>contactor on the firewall to absolutely shut off any possibility of the fat
>wire going to the starter chafing against baffling material or anything
>else in the event the engine decides to leave its normal upright, and
>locked position.
>
>What's a few bucks, guys? My experience with this friend of mine has made
>me a believer in steel braided fuel hose, Earl's fittings, Nomex clothing,
>and a lot of other things that may cost a few dollars extra, but could
>avoid years of skin graft surgery.
The external contactor has nothing to do with crash safety.
We recommended an external starter contactor for use with
ALL starters having modern automotive style contactor/engagement
solenoids. This policy was adopted by B&C from day-one in spite
of the fact that their new light-weight offering already had
a "useful" contactor built in. The reasoning was based on starter's
need for a low impedance path between battery and the solenoid winding
for energetic engagement of pinion gear and max performance closure
of the built in contactor mechanism. The reason for this is explained
at:
http://aeroelectric.com/articles/strtctr.pdf
The external contactor recommended is MUCH less abusive of the starter
switch. Failure of many starter manufacturers to recognize this stress
is root cause of premature failures of the ACS off-l-r-both-start
ignition switch of some years back when an AD was issued to replenish
the start switch contacts within the switch and to add a diode across
the switch to mitigate inductive effects for breaking the circuit.
The original AD placed the diode in the wrong place as I've described
in . . .
http://aeroelectric.com/articles/spikecatcher.pdf
A later edition of the AD corrected the error and repositioned the
diode. The diode only mitigates the switch-break-spike condition,
not the switch-make-inrush condition. The larger than usual inrush
is still present and is still a life limiting effect on the ACS or
any other style switch.
When PM starters came along, the wiring techniques recommended by
B&C and the 'Connection were not compatible with starter motors which
generated strong energies during wind-down and caused undesirable
delays in pinion gear engagement.
This is what prompted Figure Z-22 of
http://aeroelectric.com/articles/Rev11/AppZ_R11F.pdf
where a boost relay is used to relived panel mounted starter switches
of the stresses cited. Reasoning was that I'd much rather replace a
$5 relay under the cowl than ANY switch on the panel, especially
an off-l-r-both-start keyswitch.
I'll stand by the recommendations for wiring as show in either
Z-22 (boost relay) or any other Z-figure where and external
contactor is shown. It's a system performance, service life
and cost of ownership consideration.
------------------------------
Here's an excerpt from an earlier post . . .
I am designing my electrical system very similar to Z-11 with the exception
of the essential bus and a keyed starter. My new Lycoming engine came
with an SkyTec starter so I assume I'll need to use a relay as shown in
Z-14. Does this mean I don't need a starter contactor? Does this relay
replace the contactor or is it additional to it? Thanks
Matt
A problem arises when the starter utilizes a permanent
magnet motor. These motors are also efficient generators
During spin-down of the motor after the starter
is de-energized, the motor puts out a substantial amount
of power sufficient to KEEP the pinion gear solenoid
ENGAGED for several seconds after you release the pushbutton.
The technique described in our wiring diagrams was
developed as a compromise between maintaining good
starter solenoid/contactor performance with a variety
of starter switches.
Problems with the philosophy didn't arise until the
permanent magnet motor showed up. Again, we sought
a solution that maintained performance of the starter's
built in solenoid/contactor system that did not
transfer the system's unique loads to the circuitry
that controls the starter. Hence, the "boost" relay
described in Figure Z-22.
One COULD choose to use the boost relay with ANY
of the modern, lightweight starters that feature
electro-mechanically engaged pinion gears. This
would move the ideal alternator b-lead feedpoint
from a contactor on the firewall down to the
main power terminal of the starter solenoid/
contactor assembly.
-----------------------------------------
Bob . . .
Message 4
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Subject: | intercom ground loop? |
--> AeroElectric-List message posted by: Mickey Coggins <mick-matronics@rv8.ch>
My flightcom 403 intercom has a ground wire, and the
case itself is grounded. Will I be creating a ground
loop if the case itself is grounded to the airframe
via the panel? Should I try to isolate the intercom
from the panel?
Thanks,
--
Mickey Coggins
http://www.rv8.ch/
#82007 finishing
do not archive
Message 5
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Subject: | Re: OVM nuisance trips during engine start |
--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <nuckollsr@cox.net>
At 09:14 AM 4/4/2006 -0400, you wrote:
>--> AeroElectric-List message posted by: Ken <klehman@albedo.net>
>
> Thank you for your thoughts Bob.
>
>I considered adding a diode in series with the 392 R resistor to pull up
>the reference voltage quicker but discarded the idea. I was thinking
>that while the voltage was rising immediately after cranking, such a
>diode would give the trigger voltage a 0.6 volt headstart so to speak.
>As you point out though that doesn't matter if the reference voltage
>doesn't sag in the first place. Have to check again but I think I'm just
>barely seeing over 12 volts at the time that I start cranking so not
>much headroom to bring the ref. voltage up to 12 volts before cranking.
>Maybe there's a schottky type diode in my junk pile... er..parts bin.
>This is an EFI engine so it does not normally need much cranking. I will
>try this diode on one of the OVM's this morning but it will take awhile
>before I know whether it does the trick.
I don't think there's an issue with how fast the ref
voltage comes up, we just want to keep it from being pulled down
during the locked-rotor inrush current that every starter imposes
on a battery for the first few milliseconds while the motor
is spinning up. See:
http://www.aeroelectric.com/Pictures/Curves/99_Saturn_SL1.jpg
Here we see bus voltage dipping to 7.5 volts and it takes
about 600 mS before the voltage rises above 12v. All during
this time, vref in the ov module is going to be something
lower than 12v. 392 ohms and 22uf has a time constant of
8.6 milliseconds; the brownout interval is significantly longer.
http://www.aeroelectric.com/Pictures/Curves/99_Saturn_SL1_2.gif
This is a tighter view that shows the slope of the voltage
during starter spin-up.
There's no 'load' on Vref, it's a sinking reference that's
keeping the ref point from rising at trip time. The only reason
for the 392 resistor is to bias the zener into a low impedance
region of relatively stable voltage. You could replace the 392
ohm resistor with something much higher and also make the 'problem'
go away . . . but Vref will fall slightly with the lower bias
current and have a slight effect on setpoint stability.
I think the diode in series is the best bet. A 1N4000 series
would be fine . . . or a 1N4148/914 would work good too. What
ever you can put your hands on easiest.
>My analog scope is not the greatest tool for capturing one shot
>transients. I've been searching for a low cost portable or laptop DSO
>for the last couple of days as I'd also like some proof that my ignition
>is not occasionally missing a beat. There are a couple of offerings that
>seem like they might be useful in the $200 to $400. range. The
>megasquirt backup fuel injection that I'm using has datalog capability
>to a laptop and that is opening my eyes a bit to how useful digital
>recording can be.
You got that right. I beat that drum every chance I get at RAC.
We've been able to walk up to a $30,000 car for 20 years, plug
in and have it spill it's guts. We STILL can't do that on a
$5-$20 million bizjet's systems.
Keep an eye on ebay for a TDS-210 scope. GREAT value. Even at
new prices, the TDS-210 cost 1/2 of the first good scope I
ever owned and it does 10 times as much. If the tornado
sirens go off while I'm at the bench, the TDS-210 goes with
me to the 'fraid-hole with me.
Bob . . .
Message 6
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Subject: | B&C SD 8 alternator |
--> AeroElectric-List message posted by: "Chris Hukill" <cjhukill@cox.net>
Has anyone installed the B&C SD8 alternator on the RV10? I am trying to determine
if there is any interference problems with the firewall.
Thanks for any info.
Chris Hukill
Message 7
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Subject: | Re: power for headsets |
--> AeroElectric-List message posted by: James Freeman <flyeyes@mac.com>
On Apr 1, 2006, at 8:33 AM, Mickey Coggins wrote:
> --> AeroElectric-List message posted by: Mickey Coggins <mick-
> matronics@rv8.ch>
>
> I'm about to install the headset and mic jacks, and I'm
> wondering if there is an "industry standard" way to
> provide power for ANR type headsets. I've got the
> Bose, and they want USD 31 for a special jack, and
> USD 195 for the new headset cord. That would buy
> a lot of batteries.
>
> Is there a better way?
>
> Thanks!
> --
> Mickey Coggins
> http://www.rv8.ch/
> #82007 finishing
>
Mickey--the Bose (a.k.a. "Redel") connectors are rapidly becoming a
de facto standard in new factory GA aircraft. I have flown or ridden
on four fixed-wing aircraft and two helicopters built since '03 and
all had the "bose" connectors paralleled to the old standard headset
jacks. They work fine in parallel, and you can mix and match
headsets on then intercom.
When I fly the Cirrus, I use Telex ANR headsets with the new
connector, and I usually use an old Bose headset in the RV with a
battery pack.
As I type this, I have two of the Bose connectors sitting on my desk,
waiting for a rainy day to install them in the RV-8.
All of the headset manufacturers (Bose, Telex, Lightspeed, and Peltor
at least) will sell a headset wired this way. If you can build an
airplane, you can install the connector yourself.
You could also buy a female plug like the one in the battery pack for
your Bose and wire that for power (If you have the old ones with a
separate battery pack)
James
Message 8
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Subject: | power for headsets |
--> AeroElectric-List message posted by: "Alan K. Adamson" <aadamson@highrf.com>
one note on this.
I believe the DC also uses a similar jack - HOWEVER, there are 8 pin and 6
pin. To my knowledge, only DC uses the 8. Everyone else uses the 6 (better
known as the Bose connector).
Alan
-----Original Message-----
From: owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of James
Freeman
Sent: Tuesday, April 04, 2006 10:34 PM
Subject: Re: AeroElectric-List: power for headsets
--> AeroElectric-List message posted by: James Freeman <flyeyes@mac.com>
On Apr 1, 2006, at 8:33 AM, Mickey Coggins wrote:
> --> AeroElectric-List message posted by: Mickey Coggins <mick-
> matronics@rv8.ch>
>
> I'm about to install the headset and mic jacks, and I'm wondering if
> there is an "industry standard" way to provide power for ANR type
> headsets. I've got the Bose, and they want USD 31 for a special jack,
> and USD 195 for the new headset cord. That would buy a lot of
> batteries.
>
> Is there a better way?
>
> Thanks!
> --
> Mickey Coggins
> http://www.rv8.ch/
> #82007 finishing
>
Mickey--the Bose (a.k.a. "Redel") connectors are rapidly becoming a
de facto standard in new factory GA aircraft. I have flown or ridden
on four fixed-wing aircraft and two helicopters built since '03 and
all had the "bose" connectors paralleled to the old standard headset
jacks. They work fine in parallel, and you can mix and match
headsets on then intercom.
When I fly the Cirrus, I use Telex ANR headsets with the new
connector, and I usually use an old Bose headset in the RV with a
battery pack.
As I type this, I have two of the Bose connectors sitting on my desk,
waiting for a rainy day to install them in the RV-8.
All of the headset manufacturers (Bose, Telex, Lightspeed, and Peltor
at least) will sell a headset wired this way. If you can build an
airplane, you can install the connector yourself.
You could also buy a female plug like the one in the battery pack for
your Bose and wire that for power (If you have the old ones with a
separate battery pack)
James
Message 9
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Subject: | B&C SD 8 alternator |
--> AeroElectric-List message posted by: "Hinde, Frank George (Corvallis)" <frank.hinde@hp.com>
It works on the 7 and come to think of it, as this is where you would
fit the standard (read God awful) vacuum pump I can't see why it would
not fit.
Frank
Do not archive
-----Original Message-----
From: owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Chris
Hukill
Sent: Tuesday, April 04, 2006 5:14 PM
Subject: AeroElectric-List: B&C SD 8 alternator
--> AeroElectric-List message posted by: "Chris Hukill"
--> <cjhukill@cox.net>
Has anyone installed the B&C SD8 alternator on the RV10? I am trying to
determine if there is any interference problems with the firewall.
Thanks for any info.
Chris Hukill
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