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hammer408(at)comcast.net
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 Posted: Sun Mar 01, 2009 9:48 am Post subject: Wiring / Relay Question |
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Bob
I've placed my Battery Bus Firewall forward next to the Battery Contactor,
just above the 60 amp current limiter. I have a 14 g (15 amp) wire going
from battery bus thru firewall to a 7104 relay, as per the Heavy Duty E bus
configuration.
My question, should I use an additional relay or "something" between the
Battery Bus (15amp - 14 g wire)-firewall forward - and the relay which is
next to my E-Bus - mounted on sub-panel - for added safety?
Thanks
Henry
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nuckolls.bob(at)aeroelect
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| Posted: Wed Mar 04, 2009 6:02 am Post subject: Wiring / Relay Question |
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At 02:50 PM 3/1/2009, you wrote:
| Quote: |
<hammer408(at)comcast.net>
Bob
I've placed my Battery Bus Firewall forward next to the Battery Contactor,
just above the 60 amp current limiter. I have a 14 g (15 amp) wire going
from battery bus thru firewall to a 7104 relay, as per the Heavy Duty E bus
configuration.
|
I'm not sure I'm seeing a good mental image of
your installation. I presume the 60A limiter is
your b-lead protection, normally this goes next
to the starter contactor which is usually on
the upper port corner of the firewall co-located
with a loadmeter shunt (if you have one).
| Quote: | My question, should I use an additional relay or "something" between the
Battery Bus (15amp - 14 g wire)-firewall forward - and the relay which is
next to my E-Bus - mounted on sub-panel - for added safety?
|
If you have a relay mounted next to the e-bus
inside the aircraft, then you have it on the wrong
end of the wire. The purpose of the e-bus
alternate feed relay is to serve as a sort of
mini-battery contactor for this feed line . . .
it should be mounted as close as practical
to the battery bus fuse that feeds it.
Do I interpret correctly that your battery bus
is under the cowl?
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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hammer408(at)comcast.net
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| Posted: Sun Mar 08, 2009 7:05 am Post subject: Wiring / Relay Question |
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Bob:
Sorry for the confusion:
My battery bus IS firewall forward under the cowl. Looking at your Z-32
(Heavy Duty E-Bus Feed), I missed the "*" that represents the 6 inch rule.
My mounting is :
Battery Bus (under cowl)------(14awg )---FIREWALL ---- (14 awg)----s704-1
relay----to E-bus switch & E-Bus
( this run is about 2 1/2 feet from
Battery Bus to Relay)
I just need to ask the question - what harm would it be if I just left my
runs as depicted above. I am fused (15 amp) on the Battery side, so my
firewall penetration is protected. Or am I missing some other caveat ??
Henry
---
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nuckolls.bob(at)aeroelect
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| Posted: Sun Mar 08, 2009 12:16 pm Post subject: Wiring / Relay Question |
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At 01:08 PM 3/8/2009, you wrote:
| Quote: |
<hammer408(at)comcast.net>
Bob:
Sorry for the confusion:
My battery bus IS firewall forward under the cowl. Looking at your Z-32
(Heavy Duty E-Bus Feed), I missed the "*" that represents the 6 inch rule.
My mounting is :
Battery Bus (under cowl)------(14awg )---FIREWALL ---- (14 awg)----s704-1
relay----to E-bus switch & E-Bus
( this run is about 2 1/2 feet from
Battery Bus to Relay)
I just need to ask the question - what harm would it be if I just left my
runs as depicted above. I am fused (15 amp) on the Battery side, so my
firewall penetration is protected. Or am I missing some other caveat ??
|
It would probably cause a bureaucrat with a rulebook
to fuss but the risks are low for doing as you've
suggested. I presume you have other wires coming through
the firewall along with the e-bus feeder that are
receiving due diligence with respect to wire protection
and firewall integrity?
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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steve(at)tomasara.com
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| Posted: Mon Mar 09, 2009 5:49 am Post subject: Wiring / Relay Question |
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And there's a third option, (maybe mentioned in your book?), and that is
to put a resistor in parallel with the landing light switch to keep the
bulb warm when off via a trickle current to serve the dual purpose of
reducing cold-filament in-rush and also to increase bulb vibrational
durability. But I don't know if the trickle current would be about the
same to serve both purposes and I don't know if you come out ahead on
bulb life with a trickle current when applied to such a low duty cycle bulb.
Bob, do you have any pro/con thoughts about this approach?
Seems like this approach would make it relatively straight forward to
add a "bulb failure" warning for the landing light bulb that would work
when the switch is off (i.e. when it's still light outside and you might
have time to order a new one before your next night flight) but I'm also
guessing most bulbs fail right at turn-on...
Until I can afford to install an HID landing light, it would be nice to
have both a very bright and a high confidence landing light (I only have
one) but with traditional halogens, life and brightness seem to need to
be traded off with each other...
Steve.
*
| Quote: | **At 01:03 PM 3/8/2009, you wrote:
>
>Interesting traces Bob,
>
>What do you think would have the better reliability in the field for
>a 150W halogen landing light (without a surge suppressor), A S704-1
>relay with an ~16V transient suppressor for the catch diode, or a
>S701-1 switch connecting directly to the lamp?
>I'm not sure how to trade off the bigger contacts, but they bounce
>longer, dilemma...
Gee . . . you noticed! It's a credit to your curiosity
combined with an awareness of the need for trade-offs.
I an my contemporaries were faced with thousands of
such questions over our careers . . . with input from
a host of special interests that included marketing,
purchasing, inventory management, manufacturing
engineers and other systems guys who regarded every
one else's specialty as witchcraft.
Going for lower parts count is always a good lick.
The 150W lamp presents a problem of sorts. It takes
right at 9.5A in normal operation. But given what
we know of a switch's ability to CARRY current after
the bouncing is over, I'd bet that an S701 combined
with a Cantherm MF72-3D25 inrush limiter (3 ohms
cold) will limit your inrush to under 5 amps and toss
off only 9 x .044 = 0.37 volts in operation.
See:
http://www.cantherm.com/products/thermistors/cantherm_mf72.pdf
and
http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=317-1234-ND <http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=317-1234-ND>
This would be the lowest parts count solution I can
deduce and I think it has a fair shot at satisfactory
performance.
I'll do some thinking about practical ways to mount
the inrush limiter so that it is well supported,
well connected, but not thermally deprived of the
ability to warm up.
In the GP-180, one of the guys crimped flexible
leadwires to the part, wrapped it with a couple
of layers of fiberglas door gasket for a wood
burning stove and clamped the assembly into the
inside surface of the Grimes lamp fixture housing.
Kinda clumsy but it worked. Their first efforts
took too much heat out of the thing which caused
catastrophic stresses from power dissipation.
Bob . . .
**
*
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nuckolls.bob(at)aeroelect
Guest
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| Posted: Mon Mar 09, 2009 7:18 am Post subject: Wiring / Relay Question |
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At 09:46 AM 3/9/2009, you wrote:
| Quote: |
And there's a third option, (maybe mentioned in your book?), and
that is to put a resistor in parallel with the landing light switch
to keep the bulb warm when off via a trickle current to serve the
dual purpose of reducing cold-filament in-rush and also to increase
bulb vibrational durability. But I don't know if the trickle
current would be about the same to serve both purposes and I don't
know if you come out ahead on bulb life with a trickle current when
applied to such a low duty cycle bulb.
|
| Quote: | Bob, do you have any pro/con thoughts about this approach?
|
That would work.
| Quote: | Seems like this approach would make it relatively straight forward
to add a "bulb failure" warning for the landing light bulb that
would work when the switch is off (i.e. when it's still light
outside and you might have time to order a new one before your next
night flight) but I'm also guessing most bulbs fail right at turn-on...
|
Yeah . . . but the halogens are so much tougher
than the original sealed beams, it's now quite
likely that your modern lamps will run the lifetime
of the airplane. Wig-wag service is more stringent
but still.
| Quote: | Until I can afford to install an HID landing light, it would be nice
to have both a very bright and a high confidence landing light (I
only have one) but with traditional halogens, life and brightness
seem to need to be traded off with each other...
|
By the time you're ready to install HID, you'll probably
have to make a choice between HID and LED . . . those
little guys are romping right up the capabilities ladder.
Keep in mind that it takes VERY LITTLE exterior lighting
make an effective landing on a real runway. I once took
a guy flying in our J-3 using a 6v fisherman's lantern
(3 watts!) for forward lighting. It was plenty of light
to get the wheels on the ground gently.
Study your probable mission profiles before you
launch into expensive decisions. In the mean time
a halogen lamp with inrush limiting is the least
expensive, lowest energy (doesn't consume power
when OFF) way to go.
Bob . . .
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hammer408(at)comcast.net
Guest
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| Posted: Mon Mar 09, 2009 1:22 pm Post subject: Wiring / Relay Question |
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Yes Bob:
For my firewall penetration point I have a Stainless Steel flange and use
firesleeve inside the flange with another firesleeve outside clamped
together and packed with fireproof putty. Other wires include 8 awg wire
from 60 amp current limiter to main bus. From the Battery Bus - 14 awg (15
amp) to E-Bus relay ,hobbs meter, fuel boost, co monitor, 12 volt accessory
and ELT.
Henry
---
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