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jpx(at)Qenesis.com
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 Posted: Sat Feb 23, 2008 4:24 pm Post subject: Low voltage indicator for LR3 |
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My notes from talking with someone at B&C is that pin 5 is a FET
output protected by a 1N4752 zener (which is 33V). Where does the
leakage come from ?
Jeff Page
Dream Aircraft Tundra #10
| Quote: | Time: 03:44:39 PM PST US
From: "Robert L. Nuckolls, III" <nuckolls.bob(at)cox.net>
Subject: Re: NEARLY ready for first flight
At 10:22 PM 2/20/2008 -0800, you wrote:
LEDs and incandescent lamps are not directly interchangeable
in this application. You need to add a resistor to the LR-3
terminals to get the LED to masquerade as an incandescent
device. I think 470 ohm, 1/2 watt between terminals 3 and
5 of the LR3. This applies to LEDs with built in resistors
that turn them into 12v devices.
If you're assembling your own LED indicator from scratch
then you need both a series AND a parallel resistor. Here's
one of several approaches that would work:
http://www.aeroelectric.com/Pictures/Schematics/LV_Led.jpg
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nuckolls.bob(at)cox.net
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| Posted: Sat Feb 23, 2008 9:55 pm Post subject: Low voltage indicator for LR3 |
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At 07:20 PM 2/23/2008 -0500, you wrote:
| Quote: |
My notes from talking with someone at B&C is that pin 5 is a FET
output protected by a 1N4752 zener (which is 33V). Where does the
leakage come from ?
Jeff Page
Dream Aircraft Tundra #10
|
If you study the schematic cited below, you'll see a resistor
connected from collector to base (or drain to gate if fet)
that generates an artificial leakage.
This leakage is overcome by the hard pull-down on the
LV warn comparator but insufficient to illuminate an
incandescent lamp. The purpose of that leakage is to
cause a steady illumination of the LV warn lamp should
power to the LV warn circuitry within the LR-3 be lost.
The leakage will partially bias the lamp drive and cause
the lamp to glow steady.
This design goal gets in the way of allowing an LED
to go completely dark. The tiny leakage current that
produced no light on an incandescent lamp produces
significant light in the LED. Hence, the load resistor
to make an LED look like an incandescent.
Bob . . .
| Quote: | >Time: 03:44:39 PM PST US
>From: "Robert L. Nuckolls, III" <nuckolls.bob(at)cox.net>
>Subject: Re: NEARLY ready for first flight
>At 10:22 PM 2/20/2008 -0800, you wrote:
> LEDs and incandescent lamps are not directly interchangeable
> in this application. You need to add a resistor to the LR-3
> terminals to get the LED to masquerade as an incandescent
> device. I think 470 ohm, 1/2 watt between terminals 3 and
> 5 of the LR3. This applies to LEDs with built in resistors
> that turn them into 12v devices.
>
> If you're assembling your own LED indicator from scratch
> then you need both a series AND a parallel resistor. Here's
> one of several approaches that would work:
>
> http://www.aeroelectric.com/Pictures/Schematics/LV_Led.jpg
--
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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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jpx(at)Qenesis.com
Guest
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| Posted: Sun Feb 24, 2008 3:51 pm Post subject: Low voltage indicator for LR3 |
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Hmmm. I am planning a circuit that will light that same LED when the
master or auxiliary contactor is engaged when the engine isn't running
(eg. left on after flight). They neglected to mention this bias
resistor when I called to ask about the circuitry inside. This will
change my design somewhat.
Do you know what the resistor value is ?
Thanks !
Jeff Page
Dream Aircraft Tundra #10
| Quote: | At 07:20 PM 2/23/2008 -0500, you wrote:
> My notes from talking with someone at B&C is that pin 5 is a FET
> output protected by a 1N4752 zener (which is 33V). Where does the
> leakage come from ?
> Jeff Page
> Dream Aircraft Tundra #10
If you study the schematic cited below, you'll see a resistor
connected from collector to base (or drain to gate if fet)
that generates an artificial leakage.
This leakage is overcome by the hard pull-down on the
LV warn comparator but insufficient to illuminate an
incandescent lamp. The purpose of that leakage is to
cause a steady illumination of the LV warn lamp should
power to the LV warn circuitry within the LR-3 be lost.
The leakage will partially bias the lamp drive and cause
the lamp to glow steady.
This design goal gets in the way of allowing an LED
to go completely dark. The tiny leakage current that
produced no light on an incandescent lamp produces
significant light in the LED. Hence, the load resistor
to make an LED look like an incandescent.
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cassius(at)cassius.org
Guest
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| Posted: Sun Feb 24, 2008 5:45 pm Post subject: Low voltage indicator for LR3 |
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I used a 470 ohm 1/2 W resistor (5 for $0.99 at Radio Shack) for our
installation.
Works great. LED is off most of the time; flashes when battery is
initially turned on.
-----------------
"With the possible exception of the equator, everything begins
somewhere."
C. S. Lewis
[quote] ------
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nuckolls.bob(at)cox.net
Guest
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| Posted: Mon Feb 25, 2008 5:38 pm Post subject: Low voltage indicator for LR3 |
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At 06:46 PM 2/24/2008 -0500, you wrote:
| Quote: |
Hmmm. I am planning a circuit that will light that same LED when the
master or auxiliary contactor is engaged when the engine isn't running
(eg. left on after flight). They neglected to mention this bias
resistor when I called to ask about the circuitry inside. This will
change my design somewhat.
Do you know what the resistor value is ?
|
It's big . . . but keep in mind that the current
through the resistor is multiplied by the gain
of the transistor.
If the LR-3 is getting its power from the main bus
the light will flash any time any battery is feeding
the bus -AND- the alternator is off. What's the need
for alternative "design"?
Bob . . .
| Quote: | Thanks !
Jeff Page
Dream Aircraft Tundra #10
>At 07:20 PM 2/23/2008 -0500, you wrote:
>>My notes from talking with someone at B&C is that pin 5 is a FET
>>output protected by a 1N4752 zener (which is 33V). Where does the
>>leakage come from ?
>>Jeff Page
>>Dream Aircraft Tundra #10
>
> If you study the schematic cited below, you'll see a resistor
> connected from collector to base (or drain to gate if fet)
> that generates an artificial leakage.
>
> This leakage is overcome by the hard pull-down on the
> LV warn comparator but insufficient to illuminate an
> incandescent lamp. The purpose of that leakage is to
> cause a steady illumination of the LV warn lamp should
> power to the LV warn circuitry within the LR-3 be lost.
> The leakage will partially bias the lamp drive and cause
> the lamp to glow steady.
>
> This design goal gets in the way of allowing an LED
> to go completely dark. The tiny leakage current that
> produced no light on an incandescent lamp produces
> significant light in the LED. Hence, the load resistor
> to make an LED look like an incandescent.
--
269.20.9/1295 - Release Date: 2/23/2008 9:35 PM
incoming mail is certified Virus Free.
Checked by AVG.
|
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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jpx(at)Qenesis.com
Guest
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| Posted: Thu Feb 28, 2008 2:22 pm Post subject: Low voltage indicator for LR3 |
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At 06:46 PM 2/24/2008 -0500, you wrote:
| Quote: | Hmmm. I am planning a circuit that will light that same LED when the
master or auxiliary contactor is engaged when the engine isn't running
(eg. left on after flight). They neglected to mention this bias
resistor when I called to ask about the circuitry inside. This will
change my design somewhat.
Do you know what the resistor value is ?
|
It's big . . . but keep in mind that the current
through the resistor is multiplied by the gain
of the transistor.
If the LR-3 is getting its power from the main bus
the light will flash any time any battery is feeding
the bus -AND- the alternator is off. What's the need
for alternative "design"?
Bob . . .
I am wiring per Z-13/8.
If I have a main alternator failure, the LR-3 indicator will tell me.
I switch on the Endurance bus and switch off the main bus, the
indicator will go out, since there is no power there at all.
At this point, I need to switch on the aux alternator. As drawn,
there is no low voltage indicator to show if this alternator is
working. In an emergency, I might forget to do this. I usually good
with checklists, but an indicator would be helpful.
This also means there are 3 switches I could accidentally leave on
after a flight or maintenance that would ensure a depleted battery
before the next flight.
I could have 3 indicators for the switches and 2 low voltage
indicators. However, I really only need 1 indicator that indicates
low voltage in flight while running on either alternator, acting as an
idiot light after shutdown.
By adding another pole to the endurance bus and aux alternator
switches (main bus already has a usable switched to ground pole on its
switch), I can easily sense the switch positions. However, to avoid
an indicator continuously lit in flight, these contacts need to
activate a low voltage detector with a threshold abow the normal
battery voltage, but below the charging voltage.
So depending on the value of the internal resistor driving the gate of
the FET, it could turn on my LED, which is essentially pulled to
ground from battery voltage through a 680 ohm resistor.
Jeff Page
Dream Aircraft Tundra #10
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nuckolls.bob(at)cox.net
Guest
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| Posted: Fri Feb 29, 2008 5:48 pm Post subject: Low voltage indicator for LR3 |
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| Quote: |
I am wiring per Z-13/8.
If I have a main alternator failure, the LR-3 indicator will tell me.
I switch on the Endurance bus and switch off the main bus, the
indicator will go out, since there is no power there at all.
|
Yes, but this is a plan-B activity that is only expected to
be implemented in case of a rare event . . . failure of the
main alternator.
| Quote: | At this point, I need to switch on the aux alternator. As drawn,
there is no low voltage indicator to show if this alternator is
working. In an emergency, I might forget to do this.
|
Failure of the main alternator is not an emergency. It's
an emergency only if you have no alternatives i.e, you
have no back up engine driven power source and you haven't
the foggiest notion of how long your battery will run goodies
in the endurance mode.
| Quote: | I usually good
with checklists, but an indicator would be helpful.
|
How about a voltmeter. Does one of your relatively low
power digital panel-wiggets have a voltmeter function?
| Quote: | This also means there are 3 switches I could accidentally leave on
after a flight or maintenance that would ensure a depleted battery
before the next flight.
|
Are there no electro-whizzies on the panel that stay
lit up when the endurance bus is hot? . . . and three
switches? What's going to stay on un-annunciated besides
the e-bus alternate feed switch? Oh, yeah, the aux alternator
switch being left on would leave a hundred+ millamps of draw
on the battery.
| Quote: | I could have 3 indicators for the switches and 2 low voltage
indicators. However, I really only need 1 indicator that indicates
low voltage in flight while running on either alternator, acting as an
idiot light after shutdown.
|
| Quote: | By adding another pole to the endurance bus and aux alternator
switches (main bus already has a usable switched to ground pole on its
switch), I can easily sense the switch positions. However, to avoid
an indicator continuously lit in flight, these contacts need to
activate a low voltage detector with a threshold abow the normal
battery voltage, but below the charging voltage.
So depending on the value of the internal resistor driving the gate of
the FET, it could turn on my LED, which is essentially pulled to
ground from battery voltage through a 680 ohm resistor.
|
I think you're making this more complicated than
it needs to be. If the scenario that creates the situation
you're guarding against happens every fifth flight, there's
a significant human factors consideration for adding the
extra indication/warning features. But your adding "stuff"
to a system to remind you that you've just experienced
a main alternator failure. Therefore, in addition a need for
getting out the toolbox after you land, you need additional
reminding to shut off the aux alternator and e-bus alternate
feed switches?
I considered low voltage warning lights for the e-bus architecture
some years ago but decided against it. Flying on the e-bus only
whether supported by the SD-8 or not is an extra-ordinary happening.
An event that should cause give the pilot a heightened awareness
of protocols for a sweat-free termination of the flight.
Bob . . .
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jpx(at)Qenesis.com
Guest
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| Posted: Mon Mar 03, 2008 8:18 pm Post subject: Low voltage indicator for LR3 |
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| Quote: | Failure of the main alternator is not an emergency. It's
an emergency only if you have no alternatives i.e, you
have no back up engine driven power source and you haven't
the foggiest notion of how long your battery will run goodies
in the endurance mode.
|
I can turn it into an emergency by thinking the aux alternator is
maintaining the battery when I have not remembered to turn it on.
| Quote: | How about a voltmeter. Does one of your relatively low
power digital panel-wiggets have a voltmeter function?
|
I will likely have a Dynon product, so yeah, it will have a low
voltage alarm, but idiot lights are still useful sometimes.
| Quote: | > This also means there are 3 switches I could accidentally leave on
> after a flight or maintenance that would ensure a depleted battery
> before the next flight.
Are there no electro-whizzies on the panel that stay
lit up when the endurance bus is hot? . . . and three
switches? What's going to stay on un-annunciated besides
the e-bus alternate feed switch? Oh, yeah, the aux alternator
switch being left on would leave a hundred+ millamps of draw
on the battery.
|
Yeah, the Dynon being lit up might be a good clue 
| Quote: | I think you're making this more complicated than
it needs to be. If the scenario that creates the situation
you're guarding against happens every fifth flight, there's
a significant human factors consideration for adding the
extra indication/warning features. But your adding "stuff"
to a system to remind you that you've just experienced
a main alternator failure. Therefore, in addition a need for
getting out the toolbox after you land, you need additional
reminding to shut off the aux alternator and e-bus alternate
feed switches?
|
Far more likely that I bump a switch accidentally and don't notice it
is on. With the Dynon lit up, then I suppose the only switch that
requires an indicator is the aux alternator.
| Quote: | I considered low voltage warning lights for the e-bus architecture
some years ago but decided against it. Flying on the e-bus only
whether supported by the SD-8 or not is an extra-ordinary happening.
An event that should cause give the pilot a heightened awareness
of protocols for a sweat-free termination of the flight.
|
Unfortunately, the low voltage indicator in my Cessna is the radios
going out after the battery is mostly discharged. The slight
difference between a little charge and a little discharge on a small
gauge in front of the passenger is insufficient. I do not anticipate
a engine failure, but I have had an alternator failure already in my
short flying career and one in pretty much every car I have owned. So
I would like something better in my Tundra.
Jeff Page
Dream Aircraft Tundra #10
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JohnInReno
Joined: 08 Sep 2007
Posts: 150
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| Posted: Thu Mar 06, 2008 10:57 am Post subject: Low voltage indicator for LR3 |
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My "spam can" doesn't have much in the way of a low voltage warning but
the Garmin x96 does! I found a data field that displays volts and an
alarm that allows you to set the voltage threshold.
johninreno
Jeff Page wrote:
| Quote: |
> Failure of the main alternator is not an emergency. It's
> an emergency only if you have no alternatives i.e, you
> have no back up engine driven power source and you haven't
> the foggiest notion of how long your battery will run goodies
> in the endurance mode.
|
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John Morgensen
RV-9A - Born on July 3, 2013
RV4 - for sale |
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