Today's Message Index:
----------------------
1. 05:23 AM - Re: LED Ghosting (donjohnston)
2. 05:47 AM - Re: LED Ghosting (user9253)
3. 06:14 AM - Re: Question about Electrically dependent engine and power based (user9253)
4. 06:32 AM - Re: How to decide if a heat sink is required for a Rect Bridge (Sprocket)
5. 06:51 AM - Re: Z14 question about adding in external power Piper style jack (user9253)
6. 06:58 AM - Re: LED Ghosting (donjohnston)
7. 07:07 AM - Re: Re: LED Ghosting (Richard Girard)
8. 07:28 AM - Re: Re: LED Ghosting (Eric Page)
9. 08:07 AM - Re: LED Ghosting (donjohnston)
10. 09:05 AM - Re: Re: LED Ghosting (Robert L. Nuckolls, III)
11. 09:14 AM - Re: Re: LED Ghosting (Robert L. Nuckolls, III)
12. 12:09 PM - Re: LED Ghosting (donjohnston)
13. 03:13 PM - Re: How to decide if a heat sink is required for a Rect Bridge (Jeffrey W. Skiba)
14. 03:43 PM - Re: Re: LED Ghosting (Robert L. Nuckolls, III)
15. 04:49 PM - Re: LED Ghosting (donjohnston)
16. 06:48 PM - Re: How to decide if a heat sink is required for a Rect Bridge (Robert L. Nuckolls, III)
17. 06:49 PM - Re: Re: LED Ghosting (Robert L. Nuckolls, III)
18. 07:47 PM - Re: LED Ghosting (donjohnston)
19. 09:09 PM - Re: How to decide if a heat sink is required for a Rect Bridge (Jeffrey W. Skiba)
Message 1
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Subject: | Re: LED Ghosting |
Here's (what I think is) the correct circuit. Still not sure I can integrate this
into the existing PCB though.
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=425262#425262
Attachments:
http://forums.matronics.com//files/led_circuit_3_102.pdf
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Subject: | Re: LED Ghosting |
Your LED circuit 3.pdf looks correct to me.
--------
Joe Gores
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=425266#425266
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Subject: | Re: Question about Electrically dependent engine and |
power based
There is more than one way to wire an electrically dependent engine. The important
thing is that no single failure will stop the engine. The designer must
look at each component and ask, "If this part fails, what will happen and what
is the backup plan." Connecting directly to the battery eliminates some failure
points, but still leaves the battery connections. If you want to get engine
power from a different location than the battery bus, that is OK as long as
there is a plan B in case something fails. Plan B should preferably include
automatic (diodes) switching to another source or to another path from a single
source.
--------
Joe Gores
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=425268#425268
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Subject: | Re: How to decide if a heat sink is required for a |
Rect Bridge
It looks like you will only dissipate about 5 watts continuous power, which i
s well within the capability of the device. However, when you mount it, put
about a 3x3 piece of .063 aluminum underneath as a heat spreader to protect
the composite surface. Use a tiny amount of thermal grease between the cas
e and heat spreader.
Vern
==========================
==========================
Sent from my iThing. It is responsible for all gramma and typo terrors.
> On Jun 21, 2014, at 10:25 PM, "Jeffrey W. Skiba" <jskiba@icosa.net> wrote:
>
> Okay I have these Rect Bridge
> GBPC Series
> Digikey gbpc3502a
>
> 35 amp version
>
>
> I plan I using them to connect a device from two different dc batteries
> To run a load of about 6 amps continuous
> This is a composite airframe so no place to bolt directly to metal
>
> 1) Is a heat sink required ?
> 2) Would it be a good idea if one is not required
> 3) How do we tell how big of a heat sink we need ?
>
>
> Would a digikey part number hs114 work properly ?
> How can we tell ?
>
> Thanks
> Jeff.
> =C2=C2=B7=BA~=B0=C3=AD=C2=B2,=C3=9E=C3=99=C3=8A%=C2=A2=C2=BD
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-=C3=99=C2=A5
Message 5
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Subject: | Re: Z14 question about adding in external power Piper |
style jack
Looking at figure Z-31B, Piper Style Ground Power Jack, there is no indication
that the Ground PWR Contactor is energized. Once that contactor is energized
during a jump start, it will hold through its contacts. If the pilot neglects
to open the circuit breaker (or is not aware of the need), the ground PWR contactor
coil will discharge the battery, similar to forgetting to shutting off
the master. I suggest that an indicator light be connected across the contactor
coil of the ground PWR contactor.
--------
Joe Gores
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=425270#425270
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Subject: | Re: LED Ghosting |
Definite improvement! Probably usable. There's a small range where the MOSFET
controlled LEDs go out before the others. But it's such a small range that I doubt
it's an issue.
Now I have to see if it's a doable mod to the PCB.
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=425273#425273
Message 7
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Subject: | Re: LED Ghosting |
Paul, IMHO the variance in brightness would be a distraction the pilot
would not need to deal with when any of the warning LED's started lighting.
Even if you know that brightness is not an issue the difference would draw
the eye and the thinking away from the real problem. For that reason I
would want uniform brightness, but as I said, it's just my opinion.
Rick Girard
do not archive
On Thu, Jun 19, 2014 at 3:15 PM, Fisher Paul A. <FisherPaulA@johndeere.com>
wrote:
> FisherPaulA@johndeere.com>
>
> 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
> To: aeroelectric-list@matronics.com
> 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 . . .
>
>
--
Zulu Delta
Mk IIIC
Thanks, Homer GBYM
It isn't necessary to have relatives in Kansas City in order to be unhappy.
- Groucho Marx
Message 8
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Subject: | Re: LED Ghosting |
Don,
New diagram looked perfect. Glad to hear it works acceptably well. Hope you can
bodge it into your PCB for a permanent solution!
Eric
On Jun 22, 2014, at 8:57 AM, "donjohnston" <don@velocity-xl.com> wrote:
> Definite improvement! Probably usable. There's a small range where the MOSFET
controlled LEDs go out before the others. But it's such a small range that I
doubt it's an issue.
>
> Now I have to see if it's a doable mod to the PCB.
do not archive
Message 9
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Subject: | Re: LED Ghosting |
edpav8r(at)yahoo.com wrote:
> Don,
>
> New diagram looked perfect. Glad to hear it works acceptably well. Hope you
can bodge it into your PCB for a permanent solution!
>
> Eric
Thanks. Looks like I may be able to mod the board (I wish it didn't cost so much
to get these small one-off boards made :( ).
I was worried that I was going to run into the same problem with the LR3C voltage
regulator low voltage warning. But B&C apparently did it right. A 1.5K resistor
across the LEDs eliminates the ghosting but doesn't dim the LEDs when on.
WooHoo! :D
-Don
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=425280#425280
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Subject: | Re: LED Ghosting |
Your voltage measurements confirmed that the annunciator
output from your engine analyzer is decidedly not capable
of driving an incandescent bulb . . . in fact, it appears
that this particular output is not well thought out. Have
you had any contact with the factory about this? What
brand and model analyzer are we talking about. Are the
installation manuals available on line?
>Thanks. Looks like I may be able to mod the board (I wish it didn't
>cost so much to get these small one-off boards made :( ).
Emacs!
This is the best alternative for 'buffering' the
output port as it was handed to you. The size of
the resistor still leaves some risk for 'ghosting';
there might be sufficient leakage in their output
to produce a source-gate voltage that is greater than
the threshold voltage on the FET . . . typically
on the order of 2-3 volts.
A resistor on the order of 470 ohms is suggested.
>I was worried that I was going to run into the same problem with the
>LR3C voltage regulator low voltage warning. But B&C apparently did
>it right. A 1.5K resistor across the LEDs eliminates the ghosting
>but doesn't dim the LEDs when on. WooHoo! :D
That incandescent lamp driver was designed by yours
truly about 30 years ago for some devices being
offered to Cessna and Beech . . . it got folded into
the B&C products when I did their early designs.
But nobody was driving LEDs back then. Turn-off
resistors had to be added to accomodate the
conversion.
The FET buffer is the obvious 'fix' in this instance
but should not have been necessary.
Bob . . .
Message 11
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Subject: | Re: LED Ghosting |
At 08:57 AM 6/22/2014, you wrote:
>
>Definite improvement! Probably usable. There's a small range where
>the MOSFET controlled LEDs go out before the others.
The Perhelion dimmer is linear as opposed to duty-cycle
switched so yes, at some lower voltage, the gate-turn-on voltage
for the FET becomes a significant part of the supply
voltage out of the dimmer and LEDs controlled by the FET
will go out first.
A refinement of the design could consider duty-cycle
switched dimming or going to logic-level gate FET with
a much lower threshold voltage.
This has been an excellent study in the relative chaos
that can arise from poorly tested products. We were
recently discussing how poorly designed tachometer
circuits for sampling ignition signals can add risk
affecting engine performance.
This "ghosting" problem is a case where less than passing
grades on a manufacturer's homework caused a lot of unnecessary
work-arounds that are STILL less than ideal.
Bob . . .
Message 12
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Subject: | Re: LED Ghosting |
nuckolls.bob(at)aeroelect wrote:
> Your voltage measurements confirmed that the annunciator
> output from your engine analyzer is decidedly not capable
> of driving an incandescent bulb . . . in fact, it appears
> that this particular output is not well thought out. Have
> you had any contact with the factory about this? What
> brand and model analyzer are we talking about. Are the
> installation manuals available on line?
But... It does work with an incandescent bulb... As long as it's wired to 12v
and not a dimmer.
The Engine Analyzer is a Grand Rapids EIS 6000.
Doc's are here:
http://grtavionics.com/manualseis.html
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=425291#425291
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Subject: | How to decide if a heat sink is required for a |
Rect Bridge
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ClRoYW5rcw0KDQpKZWZmLg0K
Message 14
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Subject: | Re: LED Ghosting |
At 02:08 PM 6/22/2014, you wrote:
>
>
>nuckolls.bob(at)aeroelect wrote:
> > Your voltage measurements confirmed that the annunciator
> > output from your engine analyzer is decidedly not capable
> > of driving an incandescent bulb . . . in fact, it appears
> > that this particular output is not well thought out. Have
> > you had any contact with the factory about this? What
> > brand and model analyzer are we talking about. Are the
> > installation manuals available on line?
>
>
>But... It does work with an incandescent bulb... As long as it's
>wired to 12v and not a dimmer.
??? What size of bulb . . . how many milliamps
does the bulb draw?
The voltages you observed in circuit 2 say
that with JUST the two LEDS and their companion
resistor attached to the engine analyzer, all
measured voltage drops add up to the supply
voltage. This means that for that current level,
the engine analyzer will pull the lamp port
nearly to ground. I believe the resistor was
390 ohms . . . so load on the engine analyzer
in case #1 was 8.07/390 = 20.6 milliamps.
You added a resistor across the array in case
#3 which says that voltage across the 390 ohm
resistor dropped to 6.55 volts . . . so indeed,
current through the lamps went down to 6.55/390
equals 7.2 millimaps . . . approximately 1/3
that of case #1. Further, you cite 10.7 volts
across the 1K resistor for an additional
10.7 milliamps of load on the engine analyzer
lamp port . . . for a total of 17.9 milliamps
which is less than case #1. Yet you LOST some
voltage in the engine analyzer. Total voltage
drop in the lamps and resistor is 10.65 volts
with a system voltage of 12.37 . . . or 1.72
volts went missing in the engine analyzer's
lamp driver. In case #4 we see the same thing
happening . . . with the disappearance of about
1.5 volts.
The output switching device should not have that
much loss . . . I would expect tens of millvolts
tops. The voltages say yes, the LEDs are indeed
biased up significantly lighter when the anti-
ghosting resistor is added. But it's not clear
why.
>The Engine Analyzer is a Grand Rapids EIS 6000.
>Doc's are here:
>http://grtavionics.com/manualseis.html
>
Okay, the warning light output is described thusly:
Emacs!
The fact that it can 'shut down' automatically implies
some kind of protective 'smarts' on this pin. At the same
time, the rated switching current is more than
adequate to the task of handling either LED or incandescent
lamps . . . although the 'ghosting' phenomenon is not
understood.
Have you talked with GR about this? This still not
making sense.
Bob . . .
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Subject: | Re: LED Ghosting |
nuckolls.bob(at)aeroelect wrote:
> ??? What size of bulb . . . how many milliamps does the bulb draw?
>
> The voltages you observed in circuit 2 say that with JUST the two LEDS and their
companion resistor attached to the engine analyzer, all measured voltage drops
add up to the supply voltage. This means that for that current level, the
engine analyzer will pull the lamp port nearly to ground. I believe the resistor
was 390 ohms . . . so load on the engine analyzer in case #1 was 8.07/390
= 20.6 milliamps.
>
> You added a resistor across the array in case #3 which says that voltage across
the 390 ohm resistor dropped to 6.55 volts . . . so indeed, current through
the lamps went down to 6.55/390 equals 7.2 millimaps . . . approximately 1/3
that of case #1. Further, you cite 10.7 volts across the 1K resistor for an additional
10.7 milliamps of load on the engine analyzer lamp port . . . for a total
of 17.9 milliamps which is less than case #1. Yet you LOST some voltage in
the engine analyzer. Total voltage drop in the lamps and resistor is 10.65 volts
with a system voltage of 12.37 . . . or 1.72 volts went missing in the engine
analyzer's lamp driver. In case #4 we see the same thing happening . . .
with the disappearance of about 1.5 volts.
>
> The output switching device should not have that much loss . . . I would expect
tens of millvolts tops. The voltages say yes, the LEDs are indeed biased up
significantly lighter when the anti-ghosting resistor is added. But it's not
clear why.
>
> Have you talked with GR about this? This still not making sense.
> Bob . . .
The bulb I used is a bulb that I got from B&C with the LR3C. I hooked it up just
to see if it would behave properly (and it did). If you want, I can check
the specs on it.
I can't speak to or dispute the numbers or calculations that you present as that's
not my area of expertise. I can only say with certainty what happens when
the switch is thrown.
I have spoken to GRT as I mentioned in the original post. They said the alarm output
is designed for an incandescent bulb and that to make it work with an LED
I would have to put a 1.5K resistor across the LED. Now I didn't explain complex
(elaborate, convoluted, bizarre, whatever term you wish to use to describe
my annunicator panel) nature of the warning light I had. Only that I was using
an LED. They would have assumed that it was a single LED powered by a constant
power source.
I appreciate all the help and suggestions from everyone. I wish that this would
have been a simple fix but it would seem that something is going on inside the
engine analyzer that defies explanation.
-Don
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=425298#425298
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Subject: | How to decide if a heat sink is required for |
a Rect Bridge
At 05:11 PM 6/22/2014, you wrote:
In addition to the below: how do you know if you have to have a heat sink
Insulator ??? Do we have to with this type of installation ?
I originally was going to mount each one on
its own heat sink but now I am thinking all
three on the same heat sink, am I asking for electrical sparks ??
Why so many? Can you share a sketch of your
application?
Subject: AeroElectric-List: How to decide if a
heat sink is required for a Rect Bridge
Okay I have these Rect Bridge
GBPC Series
Digikey gbpc3502a
35 amp version
At 6A continuous in these devices, no heat sinking
is necessary
I plan on using them to connect a device from two different dc batteries
To run a load of about 6 amps continuous
This is a composite airframe so no place to bolt directly to metal
1) Is a heat sink required ?
2) Would it be a good idea if one is not required
3) How do we tell how big of a heat sink we need ?
Would a digikey part number hs114 work properly ?
How can we tell ?
If you were really pressing them to their
electrical limits, there ARE thermal dissipation
studies you can conduct to establish heat-sink
sizing. Here is but one of many examples . . .
http://tinyurl.com/lkly23x
These devices were chosen decades ago for
their mechanical conveniences in mounting
and attaching wires. The fact that they were
electrically ubber-robust wasn't a design
goal . . . it just turned out that way.
Unless they're mounted in a hot environment,
they're good for 6A without additional sinking.
Bob . . .
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Subject: | Re: LED Ghosting |
>
>I appreciate all the help and suggestions from everyone. I wish that
>this would have been a simple fix but it would seem that something
>is going on inside the engine analyzer that defies explanation.
Actually, it's very explainable . . . given all
the facts. Can you give me a name/number at GRT?
Bob . . .
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Subject: | Re: LED Ghosting |
Phone number for GRT is on their contact page.
http://www.grtavionics.com/contact.html
I don't recall who I spoke to about this.
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=425304#425304
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Subject: | How to decide if a heat sink is required for |
a Rect Bridge
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