Today's Message Index:
----------------------
1. 12:28 AM - Re: Re: isolation circuit (Robert L. Nuckolls, III)
2. 04:19 AM - Re: isolation circuit (jamesneely)
3. 06:36 AM - Re: "Hockey Puck" GPS receiver that uses RS-232 (Glaeser, Dennis A)
4. 08:20 AM - Re: Re: "Hockey Puck" GPS receiver that uses RS-232 ()
5. 10:38 AM - Polyfuses for aircraft? (Robert L. Nuckolls, III)
6. 01:33 PM - Re: Polyfuses for aircraft? (bcondrey)
7. 01:34 PM - Fusible Links and Bus Interconnects (tx_jayhawk)
8. 02:29 PM - Re: Fusible Links and Bus Interconnects (Robert L. Nuckolls, III)
9. 02:39 PM - Re: Re: Polyfuses for aircraft? (Robert L. Nuckolls, III)
10. 03:07 PM - Re: Re: Polyfuses for aircraft? ()
11. 04:52 PM - PA-22 system (jetech)
12. 06:39 PM - EFIS brown out protection (Paul Eckenroth)
Message 1
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| Subject: | Re: isolation circuit |
At 09:57 PM 3/25/2009, you wrote:
>
>Thanks Bob, but I'm not having any luck with that product ID. Which
>relay is it? There's a dpdt miniature part #275-249
>James
>
Hmmmm . . . I guess I don't know where you are located.
That website link was to a Radio Shack part. The relay
is a sealed, low power 12v, dpdt device. Do you have
access to a Radio Shack store?
The part suggested is a Tyco part. Here's the data
sheet:
http://relays.tycoelectronics.com/datasheets/OMI-2P.pdf
If you don't have access to Radio Shack then any
other small signal relay will do (2A or
less contacts).
Bob . . .
----------------------------------------)
( . . . a long habit of not thinking )
( a thing wrong, gives it a superficial )
( appearance of being right . . . )
( )
( -Thomas Paine 1776- )
----------------------------------------
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| Subject: | Re: isolation circuit |
When I tried the link it didn't get me to that part, but it looks like that's the
one I found one their site. Given the info on the data sheet, I think my problem
is solved. Thanks to you, and all the others that chimed in.
We have "the Source" here in the frozen north, a subsidiary of Radio Shack. I'll
have no trouble getting what I need.
Thanx again,
James
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=236193#236193
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| Subject: | Re: "Hockey Puck" GPS receiver that uses RS-232 |
Needless to say, I was surprised at GRT's comment about panel mounted
GPSs not sending the time, and based on your info maybe it's only IFR
units (?). They all have it of course, but obviously some don't pass
that info along in the serial data stream. I don't know why, and
haven't taken the time to investigate further.
Thanks,
Dennis
-------------------
From: Normand Biron
Date: Wed Mar 25 - 12:56 PM
The Garmin GNC250XL is a panel mount unit that sends date/time
information.
Norm
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| Subject: | Re: "Hockey Puck" GPS receiver that uses RS-232 |
For 3k you only get so much...
-----Original Message-----
From: owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of
Glaeser, Dennis A
Sent: Thursday, March 26, 2009 9:32 AM
Subject: AeroElectric-List: Re: "Hockey Puck" GPS receiver that uses
RS-232
<dennis.glaeser@eds.com>
Needless to say, I was surprised at GRT's comment about panel mounted
GPSs not sending the time, and based on your info maybe it's only IFR
units (?). They all have it of course, but obviously some don't pass
that info along in the serial data stream. I don't know why, and
haven't taken the time to investigate further.
Thanks,
Dennis
-------------------
From: Normand Biron
Date: Wed Mar 25 - 12:56 PM
The Garmin GNC250XL is a panel mount unit that sends date/time
information.
Norm
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| Subject: | Polyfuses for aircraft? |
I've been working with a variety of polyfuses
on the bench and have completed some tests in the
chamber. I've killed a few of the critters that
suffered heat-sinking effects of vibration
resistant mounting. These guys first fail shorted.
Depending on source impedance, they either pull
the supply voltage down . . . or blow up and go open.
I'll continue to evaluate mounting techniques
but I gotta tell you that I'm not enthusiastic about
these parts. It's a poor design that pivots about
assembly processes.
Decades of aviation experience have demonstrated
numerous recipes for success that have performed well.
It's unfortunate that LSE saw fit to install
the crowbar ov protection. Were it not for this
feature, there would be no good reason why these
systems couldn't be powered through 5A fuses at
the battery bus. But as soon as you add a requirement
for the 5A, crowbar-friendly breaker, robustness of
always-hot feeders from the bus must be greater than
the legacy design philosophies dictate.
If the LSE products had been designed in compliance
with Mil-STD-704/DO-160 guidelines, there would be no need
to incorporate a second layer of OV protection
and we wouldn't be having this conversation.
I'm not finished with the tinkering. However, I am 90%
sure that the parts being tested are not going to
exhibit equal-to-or-better performance than ingredients
and processes which go into demonstrable recipes for success.
LSE's recommended installation philosophies
will FUNCTION as advertised but are contrary
to contemporary aviation design philosophies for
protection of feeders in the power distribution
system. It's unlikely that the 'Connection will
recommend any alternatives for incorporating LSE
products into OBAM aircraft. Installers should
comply with LSE recommendations.
Bob . . .
----------------------------------------)
( . . . a long habit of not thinking )
( a thing wrong, gives it a superficial )
( appearance of being right . . . )
( )
( -Thomas Paine 1776- )
----------------------------------------
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| Subject: | Re: Polyfuses for aircraft? |
Bob,
Earlier you had mentioned that it would take a 30 amp fuse to guarantee that the
5 amp breaker would trip first from a crowbar event. I'm not enthusiastic about
that much current being allowed through - what CB size would be required
to guarantee that the 5 amp up front would trip first? Would a 7.5 in back be
OK or would it have to be significantly larger? Would this be of benefit over
a large (30 amp) fuse?
These wouldn't be in flight resettable devices but would reduce the amount of current
allowed in the always hot wires. In theory the only thing that they're
protecting against is a dead short in the airframe wiring since anything past
the 5 amp panel critters (wiring, maybe a switch and the actual ignition box)
would trip them first.
Bob
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=236266#236266
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| Subject: | Fusible Links and Bus Interconnects |
I was looking at an old Z drawing (Z-13/20 but that doesn't really matter for the
purpose of my question), and it raises some questions that I I am struggling
to recall the rationale.
1) What is the theory behind those connections (typically between busses and contactors)
they specify minimum length (6" or less). Examples I am thinking of
are between battery contactor and battery bus, battery bus and e-bus contactor,
e-bus contactor and standby alt shunt, etc.? Is it voltage drop along the
wire or something else?
2) There is a fusible link shown between the battery bus and e-bus contactor (which
ultimately connects to the e-bus when switched on). Since all of the loads
on the busses are separately fused, what exactly is the fusible link protecting
against?
3) I've noticed all of the designs show a fusible link in-line with the alt field
breaker. Why are two circuit protection devices in-line with no loads between
them? Seems redundant.
4) I've seen some people put fusible links in-line between the main and e-bus diode
feed. Not sure I appreciate why that is needed?
5) Are there any limits as to how short or how long the fusible links should be?
Thanks,
Scott
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=236267#236267
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| Subject: | Re: Fusible Links and Bus Interconnects |
At 03:31 PM 3/26/2009, you wrote:
>
>I was looking at an old Z drawing (Z-13/20 but that doesn't really
>matter for the purpose of my question), and it raises some questions
>that I I am struggling to recall the rationale.
>
>1) What is the theory behind those connections (typically between
>busses and contactors) they specify minimum length (6" or
>less). Examples I am thinking of are between battery contactor and
>battery bus, battery bus and e-bus contactor, e-bus contactor and
>standby alt shunt, etc.? Is it voltage drop along the wire or something else?
These notations suggest that connected devices should
be adjacent to each other. If you gotta go 10" for the
conductor, then so be it. But close proximity in
the airplane is a design goal.
>2) There is a fusible link shown between the battery bus and e-bus
>contactor (which ultimately connects to the e-bus when switched
>on). Since all of the loads on the busses are separately fused,
>what exactly is the fusible link protecting against?
Z-13/20 was eliminated from the z-figures. After
some considerable, afer-the-fact consideration I
decided I could claim to have been hung over when
I did it. It's just too clumsy. Z-12 or Z-14 are
better integrations of an SD-20 with a larger main
alternator.
>3) I've noticed all of the designs show a fusible link in-line with
>the alt field breaker. Why are two circuit protection devices
>in-line with no loads between them? Seems redundant.
Long lengths of wire (greater than 6" in the FAA
world) need some form of fault protection. Unless
your main bus is located within 6" of the breaker,
then protection is generally advised. Further, it
must be MUCH more robust than the 5A breaker which
is expected to operate FIRST during a crowbar ov event.
>4) I've seen some people put fusible links in-line between the main
>and e-bus diode feed. Not sure I appreciate why that is needed?
If it's not on my drawings, it's not advised by
me. Fuses, breakers, fusible links, polyfuses, etc
are NOT interchangeable technologies. I've shown
fusible links in a very few locations and only
after consideration for their operating characteristics.
>5) Are there any limits as to how short or how long the fusible
>links should be?
Fusible links smoke insulation. They don't want
to be too short for thermal characteristics. 6"
is a good number used on many cars. But certainly
no longer.
Bob . . .
----------------------------------------)
( . . . a long habit of not thinking )
( a thing wrong, gives it a superficial )
( appearance of being right . . . )
( )
( -Thomas Paine 1776- )
----------------------------------------
Message 9
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| Subject: | Re: Polyfuses for aircraft? |
At 03:28 PM 3/26/2009, you wrote:
><bob.condrey@baesystems.com>
>
>Bob,
>
>Earlier you had mentioned that it would take a 30 amp fuse to
>guarantee that the 5 amp breaker would trip first from a crowbar
>event. I'm not enthusiastic about that much current being allowed
>through - what CB size would be required to guarantee that the 5 amp
>up front would trip first? Would a 7.5 in back be OK or would it
>have to be significantly larger? Would this be of benefit over a
>large (30 amp) fuse?
Do your own tests. Put in any size fuse you like
and deliberately crowbar the downstream breaker.
Once you find a fuse that stays put after a half
dozen trips, go up one more size. Since this
is hard-fault protection only, you don't need to
upsize the wire. 20AWG is still good.
>These wouldn't be in flight resettable devices but would reduce the
>amount of current allowed in the always hot wires. In theory the
>only thing that they're protecting against is a dead short in the
>airframe wiring since anything past the 5 amp panel critters
>(wiring, maybe a switch and the actual ignition box) would trip them first.
Now you understand the struggle for
reconciling LSE recommendations with
contemporary design goals. I haven't figured
out a way to do it yet. There is probably some
form of polyfuse that would meet reliability
goals . . . but not the ones I have on hand
now. Assuming the magic device could be identified,
now we need to insure that folks can get them
and that other folks don't substitute them.
I don't like "fine tuning" a design like this.
I'm working a serious accident right now that
involved total loss of dual electronic ignition
where rudimentary design goals were not established,
understood and met.
Risk of engine failure due poor hacks is greater
than risk of fire if you roll it up into a ball.
Until some better idea emerges, wire it per
LSE recommendations . . .
Bob . . .
----------------------------------------)
( . . . a long habit of not thinking )
( a thing wrong, gives it a superficial )
( appearance of being right . . . )
( )
( -Thomas Paine 1776- )
----------------------------------------
Message 10
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| Subject: | Re: Polyfuses for aircraft? |
I have also thought of testing a slow-blo (20) style ATC for this
mission. We'll give it a go. LSE likes to tie the 5 amp breaker right to
the battery post, so a bit more testing each way.
Glenn
-----Original Message-----
From: owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of
Robert L. Nuckolls, III
Sent: Thursday, March 26, 2009 5:39 PM
Subject: Re: AeroElectric-List: Re: Polyfuses for aircraft?
<nuckolls.bob@aeroelectric.com>
At 03:28 PM 3/26/2009, you wrote:
><bob.condrey@baesystems.com>
>
>Bob,
>
>Earlier you had mentioned that it would take a 30 amp fuse to
>guarantee that the 5 amp breaker would trip first from a crowbar
>event. I'm not enthusiastic about that much current being allowed
>through - what CB size would be required to guarantee that the 5 amp
>up front would trip first? Would a 7.5 in back be OK or would it
>have to be significantly larger? Would this be of benefit over a
>large (30 amp) fuse?
Do your own tests. Put in any size fuse you like
and deliberately crowbar the downstream breaker.
Once you find a fuse that stays put after a half
dozen trips, go up one more size. Since this
is hard-fault protection only, you don't need to
upsize the wire. 20AWG is still good.
>These wouldn't be in flight resettable devices but would reduce the
>amount of current allowed in the always hot wires. In theory the
>only thing that they're protecting against is a dead short in the
>airframe wiring since anything past the 5 amp panel critters
>(wiring, maybe a switch and the actual ignition box) would trip them
first.
Now you understand the struggle for
reconciling LSE recommendations with
contemporary design goals. I haven't figured
out a way to do it yet. There is probably some
form of polyfuse that would meet reliability
goals . . . but not the ones I have on hand
now. Assuming the magic device could be identified,
now we need to insure that folks can get them
and that other folks don't substitute them.
I don't like "fine tuning" a design like this.
I'm working a serious accident right now that
involved total loss of dual electronic ignition
where rudimentary design goals were not established,
understood and met.
Risk of engine failure due poor hacks is greater
than risk of fire if you roll it up into a ball.
Until some better idea emerges, wire it per
LSE recommendations . . .
Bob . . .
----------------------------------------)
( . . . a long habit of not thinking )
( a thing wrong, gives it a superficial )
( appearance of being right . . . )
( )
( -Thomas Paine 1776- )
----------------------------------------
Message 11
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|
After looking at the Z-13/8 schematic and trying to figure out the best layout
for the old tripacer I think I am close to having a initial plan.
For those not familiar with the PA-22, there is an electrical box mounted under
the pilots seat on the front side of the seat structure. This box houses the
original starter contactor, start button, regulator, and some fuses. The battery
is located under the co-pilots seat.
I would like to fit the batt bus (FH-6 block), Batt contactor, Starter contactor,
push to start, alternator current limiter, two shunts main/aux, and the relay
for the HD E-buss circuit under the seat. The push to start circuit will be
hooked from the main bus side of the batt contactor to a CB then to the starter
contactor. The CB will also be with the under seat components.
We removed the original brake cylinder from under the pilots seat so I am trying
to figure out the best method to get these components under the seat. I would
like to find some avionics tray slides and fit everything on a slide out tray,
width would be limited but there would be some depth.
The starter and alternator cables will run forward 70" and 80" to their units (Sky-tec
and L-40). The
The behind the panel components will be the main buss, E-bus, and F1 test receptacle.
On the cabin side of the firewall will be the main controller/regulator (LR3C-14),
Aux regulator (PMR1C and OV kit), and ground system (GB24).
The battery will have its original local ground.
I have a question:
Can the circuit that runs from the SD-8 shunt to the batt side of the batt contactor
instead be fused at the batt bus using an ATC fuse?
I welcome any suggestions to what I have planned so far.
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=236301#236301
Message 12
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| Subject: | EFIS brown out protection |
Would an aux battery feed to the E Buss through a solid state contactor keep
the voltage from sagging if the contactor is energized by the starter
switch. The E Buss feed from the Main Buss is through a diode.
I will appreciate any facts and/ or opinions,
Paul Eckenroth
N509RV
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