Today's Message Index:
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1. 12:30 PM - Re: Forest of Tabs in Multiple Locations (MFleming)
2. 01:01 PM - Re: Forest of Tabs in Multiple Locations (rockitdoc)
3. 08:07 PM - Common ground on LM335 doesn't work but common power does? (rparigoris)
Message 1
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| Subject: | Re: Forest of Tabs in Multiple Locations |
So, would it better if the forest of tabs was not grounded at the sub panel and
keep the connecting wire?
>From reading your book I thought it is better for all grounds to be tied to a
central ground location.
--------
Michael Fleming
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http://forums.matronics.com/viewtopic.php?p=501159#501159
Message 2
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| Subject: | Re: Forest of Tabs in Multiple Locations |
nuckolls.bob(at)aeroelect wrote:
> At 11:29 AM 3/19/2021, you wrote:
>
> >
> > A fellow RV-7 builder has a B&C forest of tabs located on the pilot side of
the firewall with battery ground attaching on the hot side.
> >
> > They also have a small cluster of tabs on the sub panel. This group of tabs
is electrically bonded to the sub panel and has a 14awg wire connecting the
sub panel tabs to the firewall tabs. This cluster on the sub panel is for the
avionics grounds.
> >
> > Should the sub panel tabs be isolated from the sub panel or is it OK the way
it is?
>
> The 14AWG jumper adds no value in a metal
> airplane. I can be deleted and avionics grounded
> at the sub-panel.
>
>
>
> Bob . . .
>
> Un impeachable logic: George Carlin asked, "If black boxes
> survive crashes, why don't they make the whole airplane
> out of that stuff?"
So, given the choice: 1) ground tab forest grounded to airframe locally at ground
tab mount, or 2) ground tab forest grounded by wire running to battery ground
at firewall, which is more 'desirable'? Either?
--------
RV14A
Began 7-23-20
Fuse and tail Completed 2-20-21
Wiring in Process
Waiting on Wings, Finish, Engine
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http://forums.matronics.com/viewtopic.php?p=501160#501160
Message 3
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| Subject: | Common ground on LM335 doesn't work but common power |
does?
Hi Group Have some Gremlins visiting at hangar and wondering why they are now playing
nice. We have a Ilec SC7 variometer. It has a momentary switch that will
measure temperature. The temperature sender is a ST LM335 temperature sender.
It I think uses Zener technology. The Ilec provides 3 volts to the sender. The
LM335 has 3 leads, power, ground and you can add a trimmer pot. We are just
using 2 legs like the factory sender is using. Now for our problem, the factory
sender wired direct works perfect. Perhaps 1 or 2 degree changes. We decided
we want 6 channels. Purchased a nice ro9tary switch from McMaster good for 2
amps and 30 volts DC. We bread boarded 6 senders with a common ground and switched
power. Channels would go bonkers from time to time. It would act like the
sender was shorted which would have temp fall way down and it would climb back
up, then do it again. We were first using a very precise power supply that
we can vary voltage. We went from 12 to 14.5 volts, same problem. We had grounds
at power supply. Then we switched grounds to the ground at Ilec. No joy. We
tried a battery, no joy. We bypassed the switch completely, no joy, it's not
the switch. We had things on a bread board, made soldered connections, no joy?
Then we decided to share power and switch grounds. All is well? Anyone have any
ideas why switching power to senders and using common ground would give problems
but sharing power and switching grounds make things OK? BTW we have a handful
of senders, we tried many, when grounds were shared random flakiness. Thx.
Ron P. P=Perplexed!
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