Today's Message Index:
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1. 05:27 AM - Re: Electrical System Schematic Review (user9253)
2. 06:33 AM - Re: Redundant Power switching (user9253)
3. 03:00 PM - 9024 Development status (Robert L. Nuckolls, III)
4. 06:16 PM - Corrected Electrical Schematic for Review (jonlaury)
5. 06:17 PM - Z-32 Question (jonlaury)
6. 08:17 PM - Re: Z-32 Question (Robert L. Nuckolls, III)
7. 08:19 PM - Re: Corrected Electrical Schematic for Review (Robert L. Nuckolls, III)
Message 1
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| Subject: | Re: Electrical System Schematic Review |
The crowbar over-voltage module needs to be in parallel with contactor coil, not
in series as drawn. The way that it is now and in the event of an over-voltage
condition, even if the module shorts out, the circuit breaker will not trip
because the contactor coil will limit the current. Another way to look at is,
if the over-voltage module is replaced with a solid piece of wire, the contactor
will still function and the circuit breaker will not trip.
Also, the diode needs to be in series with the contactor coil to prevent reverse
polarity damage from the ground power. See Bob's drawing Z-31B.
Joe
http://www.aeroelectric.com/PPS/Adobe_Architecture_Pdfs/Z31K.pdf
--------
Joe Gores
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=305725#305725
Message 2
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| Subject: | Re: Redundant Power switching |
> If I bring separate bus power legs to a DPST to feed a single load, is the current
shared (i.e. halved) on the two poles/switches?
The simple answer to your question is, no, not necessarily.
I agree with the other posts above. The problem is that it is not clear exactly
how the circuit is wired and what is trying to be accomplished. If you can
post an electrical drawing of your circuit, it will be helpful. Do not be too
concerned about switch ratings as long as they are in the ballpark. If a switch
handles 10 percent more current than its rating, that does not mean that it
will be destroyed. Its life will be shortened but that might not matter. Supposing
that the life of a switch is rated at 10,000 cycles and due to higher
than rated current, it only lasts for 5,000 cycles. It will still last as long
as the airplane. Now I am not saying that switch ratings should be ignored.
But a switch will not blow up if slightly overloaded. I would use a switch
with the proper rating if available.
Joe
--------
Joe Gores
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=305742#305742
Message 3
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| Subject: | 9024 Development status |
The ECB layout has been checked against the
schematic and we'll order proof-of-concept boards
tonight.
The package of choice turned out to be a 15-pin,
d-sub connector shell. The board assembly solders
right to the pins of the connector and the shell
snaps over the assembly.
Emacs!
The draft software description is done. My software
guy says he can comb it out for me over the next few
days.
Depending on parts selection and installed
software, this particular design can become perhaps
a dozen different products. First release of the 9024
will offer a quad function device. The user will select
the desired function with jumpers in the mating
connector. This allows the owner/operator to stock
one spare device for up to four different applications
on the airplane
This one will be fun to put together. It's got up to
25 components soldered to two sides of a .8" x 1.1"
board!
Progress is happening . . .
Bob . . .
Message 4
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| Subject: | Corrected Electrical Schematic for Review |
After review by a group member, he pointed out that my alt#2 B lead was always
hot because it was connected to the upstream side of the battery contactor. As
it 's a relatively long fat wire, he suggested a separate contactor for it.
As I was figuring where to install it, I thought that the ground power contactor
is doing nothing most of its life and could serve as the #2 alt B lead contactor
as well.
I'd be grateful if any of you could take a look at the attached to see if I'm neglecting
something.
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=305867#305867
Attachments:
http://forums.matronics.com//files/z13_8q_mine_w_40a_contactor_126.pdf
Message 5
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If the feed wire from the main batt bus to the relay is protected by the 10a fuse,
why is it marked " * " ?
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=305869#305869
Message 6
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| Subject: | Re: Z-32 Question |
At 08:17 PM 7/21/2010, you wrote:
>
>If the feed wire from the main batt bus to the relay is protected by
>the 10a fuse, why is it marked " * " ?
>
Because the 10A (or larger) fuse exceeds the legacy
rule-of-thumb for protection size of long, always
hot feeders. Hence the alternate feed source "mini-
contactor" and a short feeder between that contactor
and the battery bus.
Bob . . .
Message 7
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| Subject: | Re: Corrected Electrical Schematic for Review |
At 08:14 PM 7/21/2010, you wrote:
>
>After review by a group member, he pointed out that my alt#2 B lead
>was always hot because it was connected to the upstream side of the
>battery contactor. As it 's a relatively long fat wire, he suggested
>a separate contactor for it.
>
>As I was figuring where to install it, I thought that the ground
>power contactor is doing nothing most of its life and could serve as
>the #2 alt B lead contactor as well.
>
>I'd be grateful if any of you could take a look at the attached to
>see if I'm neglecting something.
You could do that but the contactor needs to be a 4-terminal
device wired with three diodes like a cross-feed contactor
in Z-14. The way you have it wired now, the contactor may
not be assured a power source for closing it if the alternator
doesn't self-excite. Better that coil power is assured with
the appropriate array of diodes.
Also, you need to fix the ov protection on this contactor
per remarks offered earlier.
Bob . . .
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