Today's Message Index:
----------------------
1. 05:16 AM - Indicator light circuit with push to test (donjohnston)
2. 06:42 AM - Re: Indicator light circuit with push to test (JOHN TIPTON)
3. 07:00 AM - Re: Indicator light circuit with push to test (Bob McCallum)
4. 09:16 AM - Re: Indicator light circuit with push to test (Vern Little)
5. 09:26 AM - Re: Indicator light circuit with push to test (Robert L. Nuckolls, III)
6. 09:40 AM - Re: Indicator light circuit with push to test (donjohnston)
7. 02:08 PM - Re: Re: Indicator light circuit with push to test (Robert L. Nuckolls, III)
Message 1
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| Subject: | Indicator light circuit with push to test |
I'm working on an annunciator panel circuit that will have a push-to-test function
and dimmer. No problem there. :)
The challenge that I'm having is that some of the indicators will be powered by
the line which drives the device (pitot heat, fuel pump, etc.) and others will
be switched to ground.
I'd be fine if it weren't for the push-to-test function. :(
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=402318#402318
Message 2
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| Subject: | Re: Indicator light circuit with push to test |
There are push (to test) switches out there that are two (double) pole - use
one to power circuit, and one to earth circuit:
Here are a few:
http://www.e-switch.com/product/tabid/96/productid/60/sename/mdp-16-series-modular-pushbutton-switch-interchangeable-actuators/default.aspx
John
----- Original Message -----
From: "donjohnston" <don@numa.aero>
Sent: Sunday, June 09, 2013 1:15 PM
Subject: AeroElectric-List: Indicator light circuit with push to test
>
> I'm working on an annunciator panel circuit that will have a push-to-test
> function and dimmer. No problem there. :)
>
> The challenge that I'm having is that some of the indicators will be
> powered by the line which drives the device (pitot heat, fuel pump, etc.)
> and others will be switched to ground.
>
> I'd be fine if it weren't for the push-to-test function. :(
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=402318#402318
>
>
>
Message 3
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| Subject: | Indicator light circuit with push to test |
Don;
You indicate that "push to test" is no problem for you, but you're
struggling with the opposite polarities. One method would be to duplicate
whatever circuitry you intend to connect all of your indicators together to
accomplish the push to test on the other side of those lamps which are
switched opposite. Use a double pole "push to test" button with one pole
switching the "live" side lamps and the other pole switching the "ground"
side lamps.
Bob McC
> -----Original Message-----
> From: owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-
> server@matronics.com] On Behalf Of donjohnston
> Sent: Sunday, June 09, 2013 8:15 AM
> To: aeroelectric-list@matronics.com
> Subject: AeroElectric-List: Indicator light circuit with push to test
>
>
> I'm working on an annunciator panel circuit that will have a push-to-test
function and
> dimmer. No problem there. :)
>
> The challenge that I'm having is that some of the indicators will be
powered by the
> line which drives the device (pitot heat, fuel pump, etc.) and others will
be switched
> to ground.
>
> I'd be fine if it weren't for the push-to-test function. :(
>
>
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=402318#402318
>
>
>
>
>
>
>
> _-
> ====================================================
> ======
> _-
> ====================================================
> ======
> _-
> ====================================================
> ======
> _-
> ====================================================
> ======
>
>
Message 4
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| Subject: | Re: Indicator light circuit with push to test |
Here's what you need:
http://store.makerplane.org/annunciator-controller-il-4a-kitset/
This design provides for active high or active low inputs, push to test and
supports the connection of an external dimmer for night ops.
Vern
-----Original Message-----
From: donjohnston
Sent: Sunday, June 09, 2013 5:15 AM
Subject: AeroElectric-List: Indicator light circuit with push to test
I'm working on an annunciator panel circuit that will have a push-to-test
function and dimmer. No problem there. :)
The challenge that I'm having is that some of the indicators will be powered
by the line which drives the device (pitot heat, fuel pump, etc.) and others
will be switched to ground.
I'd be fine if it weren't for the push-to-test function. :(
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=402318#402318
-----
No virus found in this message.
Checked by AVG - www.avg.com
Message 5
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| Subject: | Re: Indicator light circuit with push to test |
At 07:15 AM 6/9/2013, you wrote:
>
>I'm working on an annunciator panel circuit that will have a
>push-to-test function and dimmer. No problem there. :)
>
>The challenge that I'm having is that some of the indicators will be
>powered by the line which drives the device (pitot heat, fuel pump,
>etc.) and others will be switched to ground.
>
>I'd be fine if it weren't for the push-to-test function. :(
Are these lamps incandescent or LED? Keep in mind that
the original application of lamps as annunciators for
important functions could not escape the fact that
a lamp's filament had a demonstrated service life which
was a tiny fraction of that for an airframe. It was prudent to
'test' each lamp before takeoff (or in flight should
a questionable condition be noted) to make sure that
the filament was intact and the lamp was CAPABLE of
doing its assigned task. Hence, legacy design philosophies
have birthed a plethora of press-to-test techniques.
Emacs!
The fixture shown above has a press-to-test feature
built in . . . which does a fine job of testing the
lamp. But what drives the lamp? A canopy open warning
switch, an low oil pressure switch, low voltage warning?
What confidence is gained for system performance knowing
that the lamp is good when the device driving that lamp
is subject to its own, possibly hidden failures?
PTT for lamps made sense when lamps had an MTBF that
was a fraction of that for the constellation of
other devices in the airplane. With LED annunciators,
the philosophy putting dip-sticks into system
functionality in pre-flight are changed.
Low oil pressure should be illuminated before the
engine is started. The canopy unlocked light can
be 'tested' by observing the condition of the light
after the master switch is on but before the canopy
is locked. Low volts light will be illuminated any
time the master is on but engine not running.
In other words, the greatest confidence in assessing
system integrity calls for and end-to-end testing
of the annunciated condition. This philosophy is
valid irrespective of the type of lamp used. Better
to poke a stick at the warning SENSOR and see
that it lights the lamp than to push a button that
lights all lamps thus encouraging you to believe that
all is right with the universe.
So before you spend $time$ and panel space crafting
a PTT system, see if you can figure out a way to build
end-to-end, check list functionality testing into all
the annunciated conditions before taking the active
for departure.
Bob . . .
Message 6
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| Subject: | Re: Indicator light circuit with push to test |
Hey Bob,
This will be a backlit panel using LEDs (Green, Red or Amber).
I see you point about the reliability of LEDs versus incandescent bulbs and that
makes perfect sense.
It just seems like every panel I've seen (and I'm pretty sure some where LEDs)
had a push-to-test switch. So I was just trying to follow (what I thought) was
best practices.
Thanks,
Don
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=402335#402335
Message 7
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| Subject: | Re: Indicator light circuit with push to test |
At 11:39 AM 6/9/2013, you wrote:
>
>Hey Bob,
>
>This will be a backlit panel using LEDs (Green, Red or Amber).
>
>I see you point about the reliability of LEDs versus incandescent
>bulbs and that makes perfect sense.
>
>It just seems like every panel I've seen (and I'm pretty sure some
>where LEDs) had a push-to-test switch. So I was just trying to
>follow (what I thought) was best practices.
Yep. That's a common feature in aviation . . . TRADITION
can plow deep furrows . . . and the young bucks are
reluctant to ask, "why is that there?" So some things
keep showing up on next year's models even when their
utility has long since passed . . . like avionics master
switches . . . battery ammeters . . . battery boxes . . .
I did have a conversation a few years ago with
a builder wanting to get some alternator noise
out of his ADF receiver. I asked why he still had
the ADF . . . did he shoot ADF approaches? No,
says he . . . he took the loop antenna off years
ago. It was already installed and he liked to
use it as an AM radio. Seems that FM reception
at altitude was problematic as stations with
shared frequencies appeared over horizon.
The noise turned out to be a ground loop in the
audio wiring. Hammers are likely to be around
for awhile too but I'm using mine less-and-less.
Bob . . .
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