Today's Message Index:
----------------------
1. 06:32 AM - Re: Off Delay Cabin Light (Eric M. Jones)
2. 07:28 AM - Re: Re: Off Delay Cabin Light (Charlie England)
3. 07:28 AM - Re: Re: Off Delay Cabin Light (Roger & Jean)
4. 09:15 AM - Re: Off Delay Cabin Light (user9253)
5. 09:15 AM - Re: Re: Off Delay Cabin Light (Robert L. Nuckolls, III)
6. 10:08 AM - fuse link to replace fuse in low current applications? (Charlie England)
7. 10:48 AM - Re: LED Ghosting (user9253)
8. 11:27 AM - Re: fuse link to replace fuse in low current applications? (Robert L. Nuckolls, III)
9. 12:02 PM - Re: Re: LED Ghosting (Robert L. Nuckolls, III)
10. 01:16 PM - Re: Re: LED Ghosting (Fisher Paul A.)
11. 01:49 PM - Re: fuse link to replace fuse in low current applications? (Charlie England)
12. 02:36 PM - Re: fuse link to replace fuse in low current applications? (Sacha)
13. 05:50 PM - Re: LED Ghosting (donjohnston)
Message 1
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Subject: | Re: Off Delay Cabin Light |
Rumen asked two things that I should have mentioned.
The mysterious resistor is the LED current-limiting resistor. Since I don't know
what LEDs you are using I can't specify it, but basically the resistor is:
R=((Vbus ) -- LED Voltage drop--1.2V) /amps you want the LEDs to run at.
This should work at 28V too. with a 35V capacitor.
You can use an amazing number of LEDs here in series/parallel, but when they turn
off and the final appearance is difficult to predict without a bench test.
So plan on that.
--------
Eric M. Jones
www.PerihelionDesign.com
113 Brentwood Drive
Southbridge, MA 01550
(508) 764-2072
emjones(at)charter.net
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=425127#425127
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Subject: | Re: Off Delay Cabin Light |
On 6/18/2014 6:21 PM, user9253 wrote:
>
> Thanks Eric, the download worked for me.
>
> --------
> Joe Gores
>
Heads up;
The link does not work if access is attempted from an email. It does
work if access is attempted from the forum.
I normally read Matt's lists via email, & couldn't load the link. I
clicked on the 'read the topic online' link, let that page load in my
browser, and then downloaded the drawing using the link in the browser page.
Charlie
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Subject: | Re: Off Delay Cabin Light |
> The mysterious resistor is the LED current-limiting resistor. Since I
> don't know what LEDs you are using I can't specify it, but basically the
> resistor is:
> R=((Vbus ) -- LED Voltage drop--1.2V) /amps you want the LEDs to run at.
>
> This should work at 28V too. with a 35V capacitor.
>
> You can use an amazing number of LEDs here in series/parallel, but when
> they turn off and the final appearance is difficult to predict without a
> bench test. So plan on that.
Eric,
another thing you might consider is connecting the
capacitor to the common on the switch and be able
to select either +12V or Ground. This would give
you the ability to use it as a delayed turn off or have
the option of instant shut off. No extra components,
just rewire the switch.
Roger
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Subject: | Re: Off Delay Cabin Light |
A diode may be required in the main 12 Volt wire. If the light is on and then
the master switch is shut off, other aircraft loads will be in parallel with R1
and short it to ground, thus no delay. If the light switch is turned on after
the master switch is shut off, then there is no power available to turn on
the transistor.
Here is the desired the desired functionality as I see it:
If the light switch is on and the master is on, then the light should stay on.
If the light switch is on, when the master is turned off, the light should stay
on for a while and then shut off automatically.
If the master has been off and then the light switch is turned on, the light should
come on for a while and then shut off automatically.
If the light switch is off, the light should be off.
Perhaps a new microprocessor-controlled product with the above features would sell.
--------
Joe Gores
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=425132#425132
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Subject: | Re: Off Delay Cabin Light |
At 06:21 PM 6/18/2014, you wrote:
>
>Thanks Eric, the download worked for me.
The LM395 is an interesting part for linear operations
but it's not a very good switch. The full-ON saturation
voltage for this part is about 1.5 volts. An alternative
on Eric's theme would use a simple MOS-Fet . . .
http://tinyurl.com/mtnd86d
In the full-ON state, voltage drop across the FET
would be quite low . . . millivolts. When given
command of the cabin light during the delay-OFF
operation, the light would stay full-ON until the
transistor begins to loose conduction as the gate
voltage falls. Assuming conductivity over a gate voltage
decay from 4 to 2 volts, the time constants shown on
the diagram will offer delay on the order of 1 to 2
minutes. Your results may vary . . . fiddle with the
size of the 1M resistor to achieve your design goals.
Bigger resistor - longer delay.
I can't imagine any LED cabin light needing more than
a couple hundred mA of operating current. The LED dome
lights in my truck only run 120 mA and are plenty
bright. At these current levels, no heat-sinking for
the FET is necessary . . . bolting it to the box
that houses the assembly will be plenty of heatsink
for up to several amps of controlled lamp load.
The only time the transistor dissipates significant
energy is during the dimming interval. All other times
it is full-OFF or full-ON and dissipates no significant heat.
Bob . . .
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Subject: | fuse link to replace fuse in low current applications? |
I'm installing an 'alternative engine' using a fuel/ignition controller
driving automotive style injectors & coil-near-plugs. My first draft for
power distribution included individual fuses & B+ lines to each coil pack
and to the injectors, to avoid one coil or injector failure taking out
multiple the coils or injectors.
Given the rarity of coil/injector failures, it seems reasonable to
eliminate the multiple joints (along with weight & wiring complexity) of
multiple fuses, & just use soldered-in fuse links instead of filling a fuse
block with fuses.
What say you?
Thanks,
Charlie
Message 7
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Subject: | Re: LED Ghosting |
Resistors can make the oil pressure LED the same brightness as the others under
one set of conditions. But when the conditions change (reduced dimmer voltage)
the brightness of all LEDs will no longer be the same.
The only way for all LEDs to have the same brightness under all conditions is if each circuit has the same components. A relay can be used to switch the oil pressure LED to make that circuit the same as the other LEDs that use mechanical contacts. Here are possible relays to use: http://tinyurl.com/pt9yd6v or http://tinyurl.com/o3g77dc or http://tinyurl.com/q28mku6
Another option is to modify the other LED circuits to match the oil pressure circuit.
Adding a diode to those other circuits might do the trick. The only way
to find out is to try it.
The relay is a sure thing but costs more and is harder to install and is less
reliable then a solid state solution. Diodes may or may not work but are very
inexpensive and easy to install.
--------
Joe Gores
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=425139#425139
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Subject: | Re: fuse link to replace fuse in low current applications? |
At 12:07 PM 6/19/2014, you wrote:
>I'm installing an 'alternative engine' using a
>fuel/ignition controller driving automotive
>style injectors & coil-near-plugs. My first
>draft for power distribution included individual
>fuses & B+ lines to each coil pack and to the
>injectors, to avoid one coil or injector failure
>taking out multiple the coils or injectors.
>
>Given the rarity of coil/injector failures, it
>seems reasonable to eliminate the multiple
>joints (along with weight & wiring complexity)
>of multiple fuses, & just use soldered-in fuse
>links instead of filling a fuse block with fuses.
It's a juggling act for risk. Your assessment appears
sound. I think I'd use butt-spliced links and put the
wires under the legacy 'fire sleeve' but that's a
process detail. What size wires make up your feeders
to the loads?
Bob . . .
Message 9
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Subject: | Re: LED Ghosting |
At 12:47 PM 6/19/2014, you wrote:
Resistors can make the oil pressure LED the same brightness as the
others under one set of conditions. But when the conditions change
(reduced dimmer voltage) the brightness of all LEDs will no longer be the same.
Quite true. Stings of led's driven in parallel from a common dimmer
will vistually track each other only when all the strings are
identical. From a pure physics perspective, LED light output is
proportional to the current in the device . . . for values at or
below the device's rated operating point.
The only way for all LEDs to have the same brightness under all
conditions is if each circuit has the same components. A relay can
be used to switch the oil pressure LED to make that circuit the same
as the other LEDs that use mechanical contacts. Here are possible
relays to use: http://tinyurl.com/pt9yd6v or
http://tinyurl.com/o3g77dc or http://tinyurl.com/q28mku6
The quest for intensity tracking between the various
indicators is purely a matter of average current through the
devices. Suppose the annunciator panel featured in the
start of this thread had two LEDs in some slots, and
single LEDs in others. It's entirely possible that they
could be made to appear identical at some level of illumination
by juggling their series resistors . . . but a bit
of pencil whipping of the numbers will show that as
supply voltage is reduced, the current through a series
string of 2 LEDs will fall off faster than for a single
LED.
The use of a relay to energize an LED string to
emulate the performance of an oil pressure
switch isn't the issue. For all practical
purposes, hard contacts and transistors produce
the same behavior when turned ON for any given
level of 'balanced' illumination. The variances
of configuration don't come into play until the
illumination is adjusted to some new value.
This is why duty cycle switched dimming works so well
for mixed configurations of LED illumination. When you duty-cycle
switch the LED, peak light output remains constant while
the eye integrates a reduced average energy into a perceived
level of brightness that will be more uniform across mixed
configurations.
I wrote the spec for a mix illumination dimmer control
for the Gates Piaggio GP-180 program where the design
goal was to dim 5v incandescent, 28v incandescent and
and 115vac electro-luminescent from a single knob.
Nobody stood up and offered a proposal for that
spec (about 1985). With micro-controllers and lookup
table driven power supplies, it could be done today
but not easily back then.
Joe is right, unless the constellation of illumination
sources have the same configuration, they will not
track each other well with simple adjustment of applied
voltage.
Bob . . .
Message 10
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Subject: | Re: LED Ghosting |
I'm confused by this thread. Back to the original issue - why is it important
that all of the LEDs in the annunciator panel have the same brightness? Don't
you just need to know if any particular one is on or off? Aren't they used to
indicate a problem? I would hope that during most flights they would all be
off. And if more than one of them was on, I certainly wouldn't be worried about
one being brighter or dimmer than another - I'd be busy looking for a place
to land!
I do appreciate the electronics discussion about the physics of getting them to
the same brightness. I just don't understand why that is important in this use
case.
Paul A. Fisher
RV7A N18PF
-----Original Message-----
From: owner-aeroelectric-list-server@matronics.com [mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Robert L. Nuckolls, III
Sent: Thursday, June 19, 2014 2:01 PM
Subject: Re: AeroElectric-List: Re: LED Ghosting
--> <nuckolls.bob@aeroelectric.com>
At 12:47 PM 6/19/2014, you wrote:
Resistors can make the oil pressure LED the same brightness as the others under
one set of conditions. But when the conditions change (reduced dimmer voltage)
the brightness of all LEDs will no longer be the same.
Quite true. Stings of led's driven in parallel from a common dimmer
will vistually track each other only when all the strings are
identical. From a pure physics perspective, LED light output is
proportional to the current in the device . . . for values at or
below the device's rated operating point.
The only way for all LEDs to have the same brightness under all conditions is if each circuit has the same components. A relay can be used to switch the oil pressure LED to make that circuit the same as the other LEDs that use mechanical contacts. Here are possible relays to use: http://tinyurl.com/pt9yd6v or http://tinyurl.com/o3g77dc or http://tinyurl.com/q28mku6
The quest for intensity tracking between the various
indicators is purely a matter of average current through the
devices. Suppose the annunciator panel featured in the
start of this thread had two LEDs in some slots, and
single LEDs in others. It's entirely possible that they
could be made to appear identical at some level of illumination
by juggling their series resistors . . . but a bit
of pencil whipping of the numbers will show that as
supply voltage is reduced, the current through a series
string of 2 LEDs will fall off faster than for a single
LED.
The use of a relay to energize an LED string to
emulate the performance of an oil pressure
switch isn't the issue. For all practical
purposes, hard contacts and transistors produce
the same behavior when turned ON for any given
level of 'balanced' illumination. The variances
of configuration don't come into play until the
illumination is adjusted to some new value.
This is why duty cycle switched dimming works so well
for mixed configurations of LED illumination. When you duty-cycle
switch the LED, peak light output remains constant while
the eye integrates a reduced average energy into a perceived
level of brightness that will be more uniform across mixed
configurations.
I wrote the spec for a mix illumination dimmer control
for the Gates Piaggio GP-180 program where the design
goal was to dim 5v incandescent, 28v incandescent and
and 115vac electro-luminescent from a single knob.
Nobody stood up and offered a proposal for that
spec (about 1985). With micro-controllers and lookup
table driven power supplies, it could be done today
but not easily back then.
Joe is right, unless the constellation of illumination
sources have the same configuration, they will not
track each other well with simple adjustment of applied
voltage.
Bob . . .
Message 11
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Subject: | Re: fuse link to replace fuse in low current applications? |
On 6/19/2014 1:26 PM, Robert L. Nuckolls, III wrote:
> <nuckolls.bob@aeroelectric.com>
>
> At 12:07 PM 6/19/2014, you wrote:
>> I'm installing an 'alternative engine' using a fuel/ignition
>> controller driving automotive style injectors & coil-near-plugs. My
>> first draft for power distribution included individual fuses & B+
>> lines to each coil pack and to the injectors, to avoid one coil or
>> injector failure taking out multiple the coils or injectors.
>>
>> Given the rarity of coil/injector failures, it seems reasonable to
>> eliminate the multiple joints (along with weight & wiring complexity)
>> of multiple fuses, & just use soldered-in fuse links instead of
>> filling a fuse block with fuses.
>
> It's a juggling act for risk. Your assessment appears
> sound. I think I'd use butt-spliced links and put the
> wires under the legacy 'fire sleeve' but that's a
> process detail. What size wires make up your feeders
> to the loads?
>
>
> Bob . . .
Design size *could* be as small as 22ga (actually, 20ga would be
adequate for a single feed to power 4 ignition coils). The injectors get
22ga to each injector.
I'd like to feed each coil & injector with 22ga, but realize that the
4-step-smaller criteria for the link is tough to achieve (26ga link).
In the 'Book', it mentions a 4-6" length for the fuse link. Any reason
not to go a bit shorter, with the link and an inch or two of the heavier
wire under the 'fire sleeve'?
Thanks,
Charlie
Message 12
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Subject: | fuse link to replace fuse in low current applications? |
> I think I'd use butt-spliced links
Bob, just curious, would solder splices also be acceptable?
Message 13
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Subject: | Re: LED Ghosting |
FisherPaulA(at)johndeere. wrote:
> I'm confused by this thread. Back to the original issue - why is it important
that all of the LEDs in the annunciator panel have the same brightness? Don't
you just need to know if any particular one is on or off? Aren't they used
to indicate a problem? I would hope that during most flights they would all be
off. And if more than one of them was on, I certainly wouldn't be worried about
one being brighter or dimmer than another - I'd be busy looking for a place
to land!
>
> I do appreciate the electronics discussion about the physics of getting them
to the same brightness. I just don't understand why that is important in this
use case.
>
> Paul A. Fisher
> RV7A N18PF
>
> --
Valid question.
The master warning panel (I should probably refer to it as an annunicator panel)
also has indicators for when the fuel pump is on and pitot heat is on (those
indicators are amber where the low oil pressure, door unsafe, etc. are red).
So you're flying along at night and you have the pitot heat or fuel pump on. The
LEDs are rather bright so you dim the indicators. Once you dim those LEDs to
a comfortable brightness, that low oil pressure LED will not illuminate at all.
Hopefully tomorrow I will be able to get the voltage readings requested. I also
got the MOSFET today so I'll give that a go as well.
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=425151#425151
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