Today's Message Index:
----------------------
1. 07:12 AM - Switches (Sam Marlow)
2. 07:51 AM - Re: Switches (Robert L. Nuckolls, III)
3. 08:03 AM - Re: Switches (Bruce Gray)
4. 09:29 AM - OVM nuisance trips during engine start (Ken)
5. 12:34 PM - Re: Dual shunts and amp gauge (Steve & Denise)
6. 08:11 PM - Re: OVM nuisance trips during engine start (Robert L. Nuckolls, III)
Message 1
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--> AeroElectric-List message posted by: Sam Marlow <sam.marlow@adelphia.net>
I'm looking for another red power switch similar to the red split rocker
Cessna type switch for my Aux battery power. Also I haven't been able to
find the wide white rocker engraved switches,as seen in the Gulf Coast
Avionics catalog. Anybody have any ideas, and yess I've Googled for
them, to confusing, with all the choices. Help would be appreciated!
Message 2
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--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <nuckollsr@cox.net>
At 10:04 AM 4/3/2006 -0400, you wrote:
>--> AeroElectric-List message posted by: Sam Marlow <sam.marlow@adelphia.net>
>
>I'm looking for another red power switch similar to the red split rocker
>Cessna type switch for my Aux battery power. Also I haven't been able to
>find the wide white rocker engraved switches,as seen in the Gulf Coast
>Avionics catalog. Anybody have any ideas, and yess I've Googled for
>them, to confusing, with all the choices. Help would be appreciated!
Carling used to make the split rocker for Cessna in a
style that matched all the other switches used on the
panel. I don't know if that was consistent throughout the
history of rockers on Cessnas products nor do I know
what they're using today.
Going with rocker switches on your project invariably locks
you down to the single supplier who offers that switch and
the style may not be available in all the popular switching
functions.
Places to begin looking include the Carling site at:
http://rocker-switches.carlingtech.com/index.asp#Full-Sized%20Rocker%20Switches
Honeywell
http://content.honeywell.com/sensing/prodinfo/tr/
NKK
http://www.nkkswitches.com/
Eaton/Cuttler-Hammer
http://commercialcontrols.eaton.com/VCBU/catalog/index.html
ITT-Cannon
http://www.ittcannon.com/products/products.asp?pid=1027&cf=pl
etc.
These listings just scratch the surface of the range
of styles and functionality of rocker switches. Once you've
identified the manufacturer of choice, you need to locate
inventory for sale. Due to the huge variability of products
by even a single manufacturer, it's unlikely that you'll find
anyone who stocks the full range of any particular product.
This is why I've advised builders to consider purchasing and
properly storing a complete set of spare rocker switches for
their project . . . especially if one selects switches from
a relatively low-profile manufacturer. This is a hedge against
style changes and/or changes of stocking distributors ideas of
what they want to keep on the shelves.
Good luck!
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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--> AeroElectric-List message posted by: "Bruce Gray" <Bruce@glasair.org>
Honeywell Microswitch AML 34 series.
Bruce
www.glasair.org
-----Original Message-----
From: owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Sam
Marlow
Sent: Monday, April 03, 2006 10:04 AM
Subject: AeroElectric-List: Switches
--> AeroElectric-List message posted by: Sam Marlow
<sam.marlow@adelphia.net>
I'm looking for another red power switch similar to the red split rocker
Cessna type switch for my Aux battery power. Also I haven't been able to
find the wide white rocker engraved switches,as seen in the Gulf Coast
Avionics catalog. Anybody have any ideas, and yess I've Googled for
them, to confusing, with all the choices. Help would be appreciated!
Message 4
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| Subject: | OVM nuisance trips during engine start |
--> 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.
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.
Ken
Message 5
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| Subject: | Re: Dual shunts and amp gauge |
--> AeroElectric-List message posted by: "Steve & Denise" <sjhdcl@kingston.net>
I countersunk the mounting holes in my 60A shunt so its no longer 'as new'.
I'll buy another one from B&C. Thanks for the offer!
Steve
RV7A
> Time: 03:45:59 PM PST US
> From: "Robert L. Nuckolls, III" <nuckollsr@cox.net>
> Subject: Re: AeroElectric-List: Dual shunts and amp gauge
>
> --> AeroElectric-List message posted by: "Robert L. Nuckolls, III"
<nuckollsr@cox.net>
>
> At 03:34 PM 4/1/2006 -0500, you wrote:
>
> >--> AeroElectric-List message posted by: "Steve & Denise"
> ><sjhdcl@kingston.net>
> >
> >I have single battery/dual alt setup. I also have EI volt/amp gauge.
> >
> >The amp gauge works using an external shunt but the value of the shunt
must
> >be known in order for
> >the gauge to work properly. Therefore my gauge is VA-1A-60, works with
> >50mV/60amp shunt.
> >
> >The shunt wires to the aux alternator lead is 50mv/10A and therefore may
not
> >work properly. I
> >would like to replace this aux shunt with 50mV/60amp so that I can switch
> >from MAIN alterntor
> >to AUX alternator and read the current on the EI gauge.
> >
> >Is there any harm in using 50mV/60amp shunt for the aux alt when
> >aeroelectric connection shows 50mv/10A?
>
> No. If you have a 10A shunt from either me or B&C, I'll
> swap it for a 60A.
>
> 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 6
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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 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 . . .
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