Today's Message Index:
----------------------
1. 05:52 AM - Re: Dimmers (John Schroeder)
2. 06:45 AM - twisted wiring (Alex Balic)
3. 06:47 AM - using the battery buss (Alex Balic)
4. 07:12 AM - Re: Dimmers (Robinson, Chad)
5. 07:53 AM - Re: using the battery buss (Robert L. Nuckolls, III)
6. 07:59 AM - Re: twisted wiring (Robert L. Nuckolls, III)
7. 08:31 AM - Re: Dimmers (Ashcraft, Keith -AES)
8. 08:32 AM - Powering LEDs (Eric M. Jones)
9. 09:09 AM - Re: Dimmers (Robert L. Nuckolls, III)
10. 09:14 AM - Dimmers (Bob Kuc)
11. 09:36 AM - Re: Dimmers (John Schroeder)
12. 09:54 AM - Re: Powering LEDs (John R)
13. 10:25 AM - Re: Powering LEDs (Robert L. Nuckolls, III)
14. 10:40 AM - Contactors (Steve Sampson)
15. 11:06 AM - Substitute for Shoo Goo (Gilles.Thesee)
16. 11:49 AM - Re: Substitute for Shoo Goo (Robert L. Nuckolls, III)
17. 03:16 PM - diodes (dschaefer1@kc.rr.com)
18. 03:31 PM - Re: Dimmers (plaurence@the-beach.net)
19. 04:44 PM - Re: Contactors (Robert L. Nuckolls, III)
20. 05:01 PM - Re: diodes (Robert L. Nuckolls, III)
21. 05:01 PM - Re: Dimmers (caspainhower@aep.com)
22. 05:05 PM - Microair 706 and Audio Iso Amp (Robert L. Nuckolls, III)
23. 05:46 PM - Updated instructions for Audio Iso Amp (Robert L. Nuckolls, III)
24. 06:14 PM - Fuel Pump Popping OV CB (Jon Finley)
25. 06:35 PM - Watsonville Seminar Nov 8/9 (Robert L. Nuckolls, III)
26. 07:28 PM - Re: Updated instructions for Audio Iso Amp (J. Oberst)
27. 08:08 PM - Re: Fuel Pump Popping OV CB (Robert L. Nuckolls, III)
28. 08:12 PM - Re: Updated instructions for Audio Iso Amp (Robert L. Nuckolls, III)
29. 09:30 PM - Alternator Noise in Headset - Epilogue? (Pete Waters)
30. 09:39 PM - Re: Updated instructions for Audio Iso Amp (caspainhower@aep.com)
Message 1
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--> AeroElectric-List message posted by: John Schroeder <jschroeder@perigee.net>
Chad -
Where is your website to see the panel?
Thanks,
do not archive.
John
On Wed, 22 Oct 2003 00:20:16 -0400, Robinson, Chad
<crobinson@rfgonline.com> wrote:
> --> AeroElectric-List message posted by: "Robinson, Chad"
> <crobinson@rfgonline.com>
>
>> I looked around on his website, and didn't see any article boosting the
>> "voltage" to an LED... and as you say, it really wouldn't do much
>> (except posssibly overheat the current-limiting resistor I suppose...)
>
> John, you made a good point about pulse width modulation (PWM) to make
> LEDs seem brighter at the same power levels, but I'd like to respond to
> this other point. Yes and no. A higher voltage WOULD make the LED
> brighter, because it's the difference between the supply voltage and the
> LED's forward voltage drop that determines the drop across the resistor,
> and thus the current flow through the whole shebang.
>
> Normally, you look at the data sheet for the LED and see that it has,
> say, a 1.7V drop and a max current rating of 50mA. So maybe you knock
> off 5mA to keep them living as long as possible and end up with 45mA.
> Now supposing you have an "ideal" main bus voltage of 13.8V. That means
> you're dropping 12.1V across the resistor. E = I * R, so 12.1V = 0.045 *
> R. Solving for R, you get a resistance of about 269 ohms. Interestingly
> enough, you can find 270 ohm resistors fairly readily (red purple
> brown), so that makes a good size.
>
> [ I didn't mean for that explanation to patronize anybody, but it's been
> a while since I last saw it mentioned, and it's sort of a regular
> question so I figured I'd make a round of it for the benefit of the
> lurkers. Bob, maybe you should make a FAQ? =) ]
>
> I think Bob's point was that even the biggest LEDs (and these are
> monsters, please note) only have a 4V drop, so there's still plenty of
> room to calculate decent limiting resistors for this (200 ohms gives you
> roughly 50mA here, for instance). So it's a puzzle as to why somebody
> would need to boost the voltage. Normally, all that matters is that
> you're a certain amount above the forward voltage drop of the diode.
>
> May I take a guess? Betcha these aren't for LEDs. Switch mode regulators
> are quite similar to the inverters used to power EL light strips, and
> I've seen a few mentions of those mentioned recently. They require AC to
> excite them, usually at anywhere from 100-400 volts, so it's definitely
> a "step up" application. Also, I looked at RST's site, at Jim Weir's
> articles, and it looks like his "mother of all lamp dimmers" was
> designed for lamps, not LEDs (although it could certainly handle both,
> to an extent).
>
> There are some advantages to both designs, but gosh, look at all the
> parts. =) With LEDs drawing as little power as they do, it's probably
> overkill. (That's a hypocritical statement for anybody who's seen my
> glass cockpit design, but what the hey. <grin>)
>
> Regards,
> Chad
>
>
--
Message 2
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--> AeroElectric-List message posted by: Alex Balic <alex157@direcway.com>
Does anyone foresee any value in twisting the strobe wiring to reduce RF
output? I know that most of the interference comes from the power supply,
and not the wire, but it seems that the high voltage pulsing within the
strobe head supply wire would cause some kind of output..... Would twisting
the wires even have an effect in this situation?
Message 3
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| Subject: | using the battery buss |
--> AeroElectric-List message posted by: Alex Balic <alex157@direcway.com>
Bob mentioned that all electronic engine controls should be run from the
Battery bus - including the fuel pumps- is the purpose of this primarily to
eliminate the contactor as a source of unwanted intermittent interruption?
Message 4
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--> AeroElectric-List message posted by: "Robinson, Chad" <crobinson@rfgonline.com>
> <... much more efficient - linear regulators dissipate any
> excess power as heat, so you use the same amount of power ...>
> <... All things considered, I'd stick with a linear design
> like B&C's ...>
> I thought a linear regulator varied the voltage to the lights
> and wouldn't work on a LED - that they are either on or off
> and you need to flash them to make them look dim. Could I
> use a linear regulator? And how is it different from a pot?
> Wondering if I'm asking the right questions now ... Jim S.
Nope, you can use a linear regulator here. Treat an LED like a light bulb with
some special characteristics, namely, voltage has to be above the forward voltage
drop or it won't turn on, and they require a current limiting resistor to
control the current flow. It's actually the CURRENT flow that determines the LED's
brightness, but we know through Ohm's law that they're related: voltage =
current * resistance.
Suppose you flipped what I said earlier about changing the resistance to make it
dimmer or brighter? Instead, you boost or drop the voltage, which is what the
regulator does? The current will naturally increase or decrease, and the LED
will get brighter or dimmer.
LEDs really have two big advantages IMHO. First, they last a very long time - not
forever, but it feels like it compared to a light bulb. They'll outlast your
plane, anyway - we're talking 100,000 hours here, depending on how much current
you shove through them, and many manufacturers list lifetime as "time to half
brightness", not even when the thing actually dies completely. Second, they
don't consume very much current all things considered, so they can be more efficient
(little to no waste heat).
There are limits to how bright they can get, though. Jeff Wilson (www.jbwilco.com/Cozyweb), a gentleman I'm collaborating with on my glass cockpit display (www.lucubration.com, although I've made progress I haven't had a chance to log - our firstborn is 7 weeks out now!) is an engineer with ST (to establish his credentials) and spent a great deal of time experimenting with arrays of white LEDs to replace wing lights. He wasn't able to find a satisfactory and cost-effective solution, at least not so far.
Regards,
Chad
Message 5
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| Subject: | Re: using the battery buss |
--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <bob.nuckolls@cox.net>
At 08:47 AM 10/22/2003 -0500, you wrote:
>--> AeroElectric-List message posted by: Alex Balic <alex157@direcway.com>
>
>Bob mentioned that all electronic engine controls should be run from the
>Battery bus - including the fuel pumps- is the purpose of this primarily to
>eliminate the contactor as a source of unwanted intermittent interruption?
That's one reason . . . but a small one.
When I walk up to a J-3 and turn ON two toggle switches, the
mags are "hot" and the engine will run. When I set down in
a Sundowner and turn the keyswitch to "BOTH", I can prop the
engine and it will run. One airplane has no electrical system,
the other has an electrical system . . . but in neither
case does the engine depend on the electrical system for
operation. When I walk up to any rental airplane available
to me, I know (because of what I carry in my flight bag)
that as long as the engine runs, I'll arrive comfortably
at an airport of my choice irrespective of any failure
in the electrical/avionics systems of that airplane.
Now, lets add some product that improves engine performance
but requires electrical power to function. Why would one willingly
give up system reliability features to acquire a modicum of
performance features? As a former owner/operator of a rental
fleet, I can tell you that I wouldn't even consider modifying
one of the airplanes with electronic ignition and/or a FADEC system.
Why? Return on investment just isn't there. Even on an airplane
that rents 30-40 hours a month, I couldn't pay for a certified
FADEC in any reasonable period of time in fuel savings. I'm
not sure the numbers would justify putting a $low$ Jeff or Klaus
ignition system on a rental machine.
All of these "enhancements" require electrical power to keep
the engine running. Therefore, any engine so fitted should
have enough independent sources of power to keep probability
of electrically induced stoppage to some level on a par
with dual magnetos of yore.
(1) We know that parts count is inversely related to
reliability. So, it behooves us to MINIMIZE parts count
between electrically critical engine components and
their power sources.
(2) It's also useful to keep engine operation as independent
as possible from electrical system operation. Suppose you
smell bad stuff in the cockpit and it's not gasoline
fumes? First reaction is to shut down the DC power master
switches . . . it's really handy if you can do this and
not have the engine continue to run.
With one or two $LOW$ ignition systems, this is pretty
easy. FADECs are more problematic. I don't know what the
REAL current requirements are for these systems but some
of the wire and fuse sizes specified by the system designers
are scarry.
Bob . . .
Message 6
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| Subject: | Re: twisted wiring |
--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <bob.nuckolls@cox.net>
At 08:44 AM 10/22/2003 -0500, you wrote:
>--> AeroElectric-List message posted by: Alex Balic <alex157@direcway.com>
>
>Does anyone foresee any value in twisting the strobe wiring to reduce RF
>output? I know that most of the interference comes from the power supply,
>and not the wire, but it seems that the high voltage pulsing within the
>strobe head supply wire would cause some kind of output..... Would twisting
>the wires even have an effect in this situation?
The shielded-triple wire supplied in the installation kits
for strobes IS twisted . . . but if it were not, it wouldn't
make any difference. Just the fact that the wires between strobe
heads and power supplies are closely bundled breaks 99% of
the noise propagation potential. Shielding takes out the
majority of the last 1%. Wether or not it's twisted is of
no practical consequence.
Most noise problems with strobes is related to audio rate
CONDUCTED noise coming out the power supply leads and propagating
around the airplane on the bus. When encountered, this noise
is easy to fix.
Bob . . .
Message 7
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--> AeroElectric-List message posted by: "Ashcraft, Keith -AES" <Keith.Ashcraft@itt.com>
Hi All,
Another way to control a LEDs brightness is to modulate its "ON" time. Still limit
the current to around 20mA, but modulate the "ON" time. PWM (pulse width modulation)
is what it is referred to. A 555 timer chip, will work, but now you
are getting into a more complicated scenario, and is it worth it?
Keith
Zenith CH701
Tail 98% --kit
All else ----scratch
N 38.9947
W 105.1305
Alt. 9,100'
Robinson, Chad wrote:
--> AeroElectric-List message posted by: "Robinson, Chad" <mailto:crobinson@rfgonline.com> <crobinson@rfgonline.com>
<... much more efficient - linear regulators dissipate any
excess power as heat, so you use the same amount of power ...>
<... All things considered, I'd stick with a linear design
like B&C's ...>
I thought a linear regulator varied the voltage to the lights
and wouldn't work on a LED - that they are either on or off
and you need to flash them to make them look dim. Could I
use a linear regulator? And how is it different from a pot?
Wondering if I'm asking the right questions now ... Jim S.
Nope, you can use a linear regulator here. Treat an LED like a light bulb with
some special characteristics, namely, voltage has to be above the forward voltage
drop or it won't turn on, and they require a current limiting resistor to
control the current flow. It's actually the CURRENT flow that determines the LED's
brightness, but we know through Ohm's law that they're related: voltage =
current * resistance.
Suppose you flipped what I said earlier about changing the resistance to make it
dimmer or brighter? Instead, you boost or drop the voltage, which is what the
regulator does? The current will naturally increase or decrease, and the LED
will get brighter or dimmer.
LEDs really have two big advantages IMHO. First, they last a very long time - not
forever, but it feels like it compared to a light bulb. They'll outlast your
plane, anyway - we're talking 100,000 hours here, depending on how much current
you shove through them, and many manufacturers list lifetime as "time to half
brightness", not even when the thing actually dies completely. Second, they
don't consume very much current all things considered, so they can be more efficient
(little to no waste heat).
There are limits to how bright they can get, though. Jeff Wilson (www.jbwilco.com/Cozyweb), a gentleman I'm collaborating with on my glass cockpit display (www.lucubration.com, although I've made progress I haven't had a chance to log - our firstborn is 7 weeks out now!) is an engineer with ST (to establish his credentials) and spent a great deal of time experimenting with arrays of white LEDs to replace wing lights. He wasn't able to find a satisfactory and cost-effective solution, at least not so far.
Regards,
Chad
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Message 8
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--> AeroElectric-List message posted by: "Eric M. Jones" <emjones@charter.net>
Remember before running off to build some led lights, that leds are DIODES
and they cannot be put in parallel, without a current limiting resistor.
The reasonable way to make an led assembly is to put several leds in series
with ONE limiting resistor.
For example-- if the power supply is 14.5V and the individual led Vf
(voltage drop) is 2 volts, you can string seven of these leds in series with
a series resistor (in this case E=IR; pick the current; 0.5V/.020A=25 ohms).
This string (whose length is limited only by the available drive voltage)
can conveniently be put into a parallel-connected assembly (whose width is
limited only by the available current). Remember to calculate the power
dissipated in the resistor (I x I x R; in this case .02 x .02 x 25=.01W).
The dissipated power in a single led operated from 14.5V at .02A would be
about 30X as much. This often fools first timers.
Squash the notion that leds need to be pulsed to change their intensity.
This errant notion comes from the way digit displays are lighted by
microprocessors. It is also electrically very noisy. Regular leds behave
pretty much like regular filament lamps to changing voltage.
One more thing to watch for! Leds usually have a poor reverse voltage
withstand, usually only 4-5 volts. So you can easily blow them up by reverse
voltage or ESD static.
I don't know what Jim Weir was thinking. It must be hard to come up with an
article every month.
Regards,
Eric M. Jones
www.PerihelionDesign.com
113 Brentwood Drive
Southbridge MA 01550-2705
Phone (508) 764-2072
Email: emjones@charter.net
"A man's got to know his limitations."
(Clint Eastwood's Dirty Harry in Magnum Force, 1973)
Message 9
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--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <bob.nuckolls@cox.net>
At 12:20 AM 10/22/2003 -0400, you wrote:
>--> AeroElectric-List message posted by: "Robinson, Chad"
><crobinson@rfgonline.com>
>
> > I looked around on his website, and didn't see any article boosting the
> > "voltage" to an LED... and as you say, it really wouldn't do much
> > (except posssibly overheat the current-limiting resistor I suppose...)
>
>John, you made a good point about pulse width modulation (PWM) to make
>LEDs seem brighter at the same power levels, but I'd like to respond to
>this other point. Yes and no. A higher voltage WOULD make the LED
>brighter, because it's the difference between the supply voltage and the
>LED's forward voltage drop that determines the drop across the resistor,
>and thus the current flow through the whole shebang.
>
>Normally, you look at the data sheet for the LED and see that it has, say,
>a 1.7V drop and a max current rating of 50mA. So maybe you knock off 5mA
>to keep them living as long as possible and end up with 45mA. Now
>supposing you have an "ideal" main bus voltage of 13.8V. That means you're
>dropping 12.1V across the resistor. E = I * R, so 12.1V = 0.045 * R.
>Solving for R, you get a resistance of about 269 ohms. Interestingly
>enough, you can find 270 ohm resistors fairly readily (red purple brown),
>so that makes a good size.
>
>[ I didn't mean for that explanation to patronize anybody, but it's been a
>while since I last saw it mentioned, and it's sort of a regular question
>so I figured I'd make a round of it for the benefit of the lurkers. Bob,
>maybe you should make a FAQ? =) ]
>
>I think Bob's point was that even the biggest LEDs (and these are
>monsters, please note) only have a 4V drop, so there's still plenty of
>room to calculate decent limiting resistors for this (200 ohms gives you
>roughly 50mA here, for instance). So it's a puzzle as to why somebody
>would need to boost the voltage. Normally, all that matters is that you're
>a certain amount above the forward voltage drop of the diode.
>
>May I take a guess? Betcha these aren't for LEDs. Switch mode regulators
>are quite similar to the inverters used to power EL light strips, and I've
>seen a few mentions of those mentioned recently. They require AC to excite
>them, usually at anywhere from 100-400 volts, so it's definitely a "step
>up" application. Also, I looked at RST's site, at Jim Weir's articles, and
>it looks like his "mother of all lamp dimmers" was designed for lamps, not
>LEDs (although it could certainly handle both, to an extent).
I've looked over Jim's schematic at:
http://www.rst-engr.com/kitplanes/KP0010/KPsch.jpg
This is a variable duty-cycle oscillator driving an array of
switches that modulate current flow through an LED/Resistor
combination.
First, let's consider the LED/Resistor combo at R8, R9, D1
A pair of 180 ohm resistors in parallel yields a combined
resistance of 90 ohms. A single 91 or 100 ohm resistor would
suffice here too . . . it's not apparent why he chooses to
parallel two devices . . . perhaps this was what he had in
the junkbox.
Okay, 14v supply fed to this resistor/lamp combo though a
saturated switch (Q2) says the current through the diode
is (14-2)/90 = 133 milliamperes. So, if the LED is rated
at 30 ma, one might reasonably deduce that maximum duty
cycle for operating at 133 mA PEAK is on the order of
22%
Now the question is, what is the apparent brightness
difference between two LEDs, on operated at 133 mA peak
and 22% and one operated at 30 mA and 100%? We do
know that the tends to be a peak intensity responder.
Its reasonable to infer that the eye might perceive
that the 133/22 lamp is brighter than the 30/100
lamp. 4x as bright? No, just because you whang
a LED at 4x its rated current doesn't mean that you
get 4x light. Even if it were 4x as bright in terms
of measured output, can you look at three lamps of
varying intensity and tell me if #1 is 2x the light
of #2 and #3 is 10x the light output of #1? I suspect
not.
I suspect this article was written some time ago and
perhaps before the virtual flood of high intensity
lamps came onto the market in a variety of colors.
I find it a weak idea to electronically fool our eyes
into believing a barely adequate single LED is superior
to running two or three LEDs . . . it's not like they
are expensive.
The strongest arguments against this technique of
intensity enhancement are: (1) What happens if a component
in the oscillator fails and the system goes to 100%
duty cycle? Do the LED go belly up? Do the resistors
smoke? and (2) what is the relative reliability of
a system that uses a single adjustable duty-cycle
controller for all of the LEDs in the system? One
part can crap and either smoke or shut down the whole
system.
The next revision to lighting chapter in the 'Connection
will touch on LEDs as primary illumination sources for
both annunicators and general panel illumination. If I were
building an airplane today, I find it attractive to
consider making the panel floods from an array of LEDs
powered from its own lithium or alkaline battery pack.
Completely independent of ship's power.
Bob . . .
Message 10
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--> AeroElectric-List message posted by: "Bob Kuc" <bkuc1@tampabay.rr.com>
Jim wrote an article on how to get more light from an LED. Basically by
flashing the LED at 120 Hz with 1/4 duty you can use higher voltage through
the LED that what it was rated for, the eye sees the brighter light as
steady.
His article can explain it much better that I can. Here is the link to
Jim's article and schematic on how to build it. It does contain a pot to
adjust the brightness http://www.rst-engr.com/kitplanes/KP0010/KP0010.htm
I used this schematic to drive three jumbo defused LEDs that allows me to
light my panel from my overhead console. While I was testing this in my
garage on late evening, my wife decided to go to bed, looked in the garage
and saw that it was dark, locked it up with me still in the garage.
Needless to say, scared the begeezus out of here when I started to bang on
the garage door :-)
----- Original Message -----
From: "Robert L. Nuckolls, III" <bob.nuckolls@cox.net>
Subject: Re: AeroElectric-List: Dimmers
> --> AeroElectric-List message posted by: "Robert L. Nuckolls, III"
<bob.nuckolls@cox.net>
>
> At 11:20 AM 10/21/2003 -0400, you wrote:
> >--> AeroElectric-List message posted by: "Bob Kuc"
<bkuc1@tampabay.rr.com>
> >
> >Jim,
> >I am doing the same thing on my velocity. However, I put my largish LEDs
in
> >the overhead console. I have three of them that light up the whole
panel.
> >While I am not flying yet, I have sat in the garage with all the lights
out
> >and it does light up the panel very nicely, but not that brightly. I am
not
> >planning on putting a dimmer on. If you look at Jim Weir's site, he had
an
> >article that used an op amp to oscillate to get a higher voltage through
the
> >LEDs.
>
> ??? Even the highest voltage LEDs are on the order of 4 volts. Can
> you describe why some kind of "boost" was necessary?
>
> Bob . . .
>
---
Message 11
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--> AeroElectric-List message posted by: John Schroeder <jschroeder@perigee.net>
Chad -
To get relatively uniform dimming/illumination from a linear regulator on
a string of LED's you should have them in parallel. Correct?
Thanks,
John
> Nope, you can use a linear regulator here. Treat an LED like a light
> bulb with some special characteristics, namely, voltage has to be above
> the forward voltage drop or it won't turn on, and they require a current
> limiting resistor to control the current flow.
Message 12
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| Subject: | Re: Powering LEDs |
--> AeroElectric-List message posted by: John R <jrourke@allied-computer.com>
Your numbers are correct in an ideal world - but if the voltage were to
fall to 12.6 or even 12 volts, the LEDs will have less than 1.7 volts
across each one (on average), and they will get *very* dim (luminance is
not linear with voltage)... I'd put no more than 5 in series (given Vled
of 2.0 volts) or maybe even only 4, so that they will always function
even in cases of power anomalies (no, I'm not going to use the word
"emergency"! :-)
But you do make a good point - much simpler than PWM, and not much
wastge heat in the resistor, since it is so much smaller. Of course I
wouldn't do a series string like this with incandescents because of the
relatively high failure rate, but LEDs are so long-lived that I think it
would be acceptable. And if you want redundancy, use two strings of 4
LEDs each, each with a current-limiting resistor of 330 ohms 1/4-watt
resistors (drop of maximum 14.5-8 volts or 6.5 volts/.02A = .13 watts)
-John R.
P.S.: BTW, I googled for "Jim Weir LED" and found the articles - he
actually covers both methods;
<http://www.rst-engr.com/kitplanes/KP0009A/KP0009A.htm> describes series
LED operation, and
<http://www.rst-engr.com/kitplanes/KP0010/KP0010.htm> shows a
dimming/boosting PWM circuit.
I think he's using the LM324 because it probably makes a bit less
electrical noise than a 555, and may be more flexible in drive
capability to multiple transistors (although I'm sure you could adapt a
555 to do something similar, still with fewer parts)
Eric M. Jones wrote:
>--> AeroElectric-List message posted by: "Eric M. Jones" <emjones@charter.net>
>
>Remember before running off to build some led lights, that leds are DIODES
>and they cannot be put in parallel, without a current limiting resistor.
>
>The reasonable way to make an led assembly is to put several leds in series
>with ONE limiting resistor.
>For example-- if the power supply is 14.5V and the individual led Vf
>(voltage drop) is 2 volts, you can string seven of these leds in series with
>a series resistor (in this case E=IR; pick the current; 0.5V/.020A=25 ohms).
>
>This string (whose length is limited only by the available drive voltage)
>can conveniently be put into a parallel-connected assembly (whose width is
>limited only by the available current). Remember to calculate the power
>dissipated in the resistor (I x I x R; in this case .02 x .02 x 25=.01W).
>The dissipated power in a single led operated from 14.5V at .02A would be
>about 30X as much. This often fools first timers.
>
>Squash the notion that leds need to be pulsed to change their intensity.
>This errant notion comes from the way digit displays are lighted by
>microprocessors. It is also electrically very noisy. Regular leds behave
>pretty much like regular filament lamps to changing voltage.
>
>One more thing to watch for! Leds usually have a poor reverse voltage
>withstand, usually only 4-5 volts. So you can easily blow them up by reverse
>voltage or ESD static.
>
>I don't know what Jim Weir was thinking. It must be hard to come up with an
>article every month.
>
>Regards,
>Eric M. Jones
>www.PerihelionDesign.com
>113 Brentwood Drive
>Southbridge MA 01550-2705
>Phone (508) 764-2072
>Email: emjones@charter.net
>
> "A man's got to know his limitations."
> (Clint Eastwood's Dirty Harry in Magnum Force, 1973)
>
>
>
>
Message 13
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| Subject: | Re: Powering LEDs |
--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <bob.nuckolls@cox.net>
>
>Squash the notion that leds need to be pulsed to change their intensity.
>This errant notion comes from the way digit displays are lighted by
>microprocessors. It is also electrically very noisy. Regular leds behave
>pretty much like regular filament lamps to changing voltage.
I don't think this was the foundation of the philosophy. At the
time the article was done, I suspect Jim was trying to increase
perceived brightness by duty-cycle switching power at an elevated
peak level . . . adjusting intensity over the min to max bright
by adjusting duty-cycle from 0% to max bright was a fallout of
the pulsed control philosophy
>One more thing to watch for! Leds usually have a poor reverse voltage
>withstand, usually only 4-5 volts. So you can easily blow them up by reverse
>voltage or ESD static.
I've not found this to be a real toe-stubber. I've run repeated
bench tests applying 30V reverse voltage to high intensity red
and white LEDs with no damage.
>I don't know what Jim Weir was thinking. It must be hard to come up with an
>article every month.
Reading from the text of his article, it WAS his intention
to take advantage of peak handling capabilities of LEDs combined
with characteristics of the human eye to get more "brightness"
without over-stressing the devices . . . a relatively cool idea
if the parts counts and failure modes were not so discouraging.
Bob . . .
Message 14
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--> AeroElectric-List message posted by: "Steve Sampson" <SSampson.SLN21@london.edu>
Why do contactors normally have one side labelled to the battery and the
other to the load? They would appear to be a symmetrical device from the
internal diagram in Bob's book.
The reason for the question is that I am wiring up the firewall of an RV9a
and am using basically diags Z9 and Z24 (to control an internally regulated
alternator). Placement of the contactor to kill the supply from the
alternator means the wiring would be simpler if the device was wired
'backwards'. In fact the current will also flow through it backwards in that
if a contactor is normally handling current flowing from a battery to
devices this contactor will be handling current flowing from an alternator
to a battery.
The specific units concerned are the VANS Master Relay and the VANS ND 60
amp alternator.
Message 15
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| Subject: | Substitute for Shoo Goo |
--> AeroElectric-List message posted by: "Gilles.Thesee" <Gilles.Thesee@ac-grenoble.fr>
Hi Bob and all,
Shoo goo is not available on this side of the pond. Do you think the regulat
glue supplied with my hot glue gun could be a good replacement ?
Thanks
Gilles Thesee
Message 16
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| Subject: | Re: Substitute for Shoo Goo |
--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <bob.nuckolls@cox.net>
At 08:05 PM 10/22/2003 +0200, you wrote:
>--> AeroElectric-List message posted by: "Gilles.Thesee"
><Gilles.Thesee@ac-grenoble.fr>
>
>Hi Bob and all,
>
>Shoo goo is not available on this side of the pond. Do you think the regulat
>glue supplied with my hot glue gun could be a good replacement ?
No, hot melts are a whole other attachment technology. The
more generic, industrial equivalent of Shoe Goo is E-6000
offered by Eclectic Products (also makes Shoe Goo). Check with
hardware and craft stores. If push comes to shove, I could
get some and send it to you. This is a unique product with
extra-ordinary capabilities. There are undoubtedly other products
with similar capabilities but I've not researched any.
Bob . . .
Message 17
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--> AeroElectric-List message posted by: dschaefer1@kc.rr.com
Bob ... can you remind me why there are so many diodes on the various
contactors? I'm building the 'all electric' airplane and don't really know
why they are there.
Regards,
David
Message 18
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--> AeroElectric-List message posted by: plaurence@the-beach.net
Hey guys,
I've got the solution.
First, use the PWM to brighten the LEDS and keep the life in the 20,000 hour range.
Second, Move to South Florida, you'll never notice the extra heat.
Cheers,
Peter
Well, I was trying to keep my reply uncharacteristically simple and
> direct... yes, a higher supply voltage will increase the Vdrop across
> the resistor, which increases the current in both the resistor and the
> LED, which increases the heat dissipated by the resistor, and light
> output of the LED... to a point. (LEDs have ratings for a reason; too
> much and they will indeed glow more brightly - for a while. Maybe even
> REAL bright. and then, real DARK! :-)
>
> But in any event, although I'm not certain what Bob's "???"
> specifically referred to (you're probably right), I was just thinking
> that if you wanted to boost an LED's output, you generally don't do it
> by throwing more voltage at it - and if you did, using an oscillator
> to do it is the long way 'round to end up at the same problem - the
> higher voltage across the resistor generates a lot of wasted heat,
> which is what we're trying to avoid.
>
> I vote for the PWM as the most likely explanation for a design
> involving an oscillator.Yes, it's somewhat more complex (although a
> 556, a few caps and resistors will do the trick nicely I should
> think), but does not create much excess heat, and can function both as
> a dimmer and a "booster".
>
> I'd like to find the article though.
>
> -John
>
>
> Robinson, Chad wrote:
>
> >--> AeroElectric-List message posted by: "Robinson, Chad"
> ><crobinson@rfgonline.com>
> >
> >
> >
> >>I looked around on his website, and didn't see any article boosting
> >>the "voltage" to an LED... and as you say, it really wouldn't do
> >>much (except posssibly overheat the current-limiting resistor I
> >>suppose...)
> >>
> >>
> >
> >John, you made a good point about pulse width modulation (PWM) to
> >make LEDs seem brighter at the same power levels, but I'd like to
> >respond to this other point. Yes and no. A higher voltage WOULD make
> >the LED brighter, because it's the difference between the supply
> >voltage and the LED's forward voltage drop that determines the drop
> >across the resistor, and thus the current flow through the whole
> >shebang.
> >
> >Normally, you look at the data sheet for the LED and see that it has,
> >say, a 1.7V drop and a max current rating of 50mA. So maybe you knock
> >off 5mA to keep them living as long as possible and end up with 45mA.
> >Now supposing you have an "ideal" main bus voltage of 13.8V. That
> >means you're dropping 12.1V across the resistor. E = I * R, so 12.1V
> >= 0.045 * R. Solving for R, you get a resistance of about 269 ohms.
> >Interestingly enough, you can find 270 ohm resistors fairly readily
> >(red purple brown), so that makes a good size.
> >
> >[ I didn't mean for that explanation to patronize anybody, but it's
> >been a while since I last saw it mentioned, and it's sort of a
> >regular question so I figured I'd make a round of it for the benefit
> >of the lurkers. Bob, maybe you should make a FAQ? =) ]
> >
> >I think Bob's point was that even the biggest LEDs (and these are
> >monsters, please note) only have a 4V drop, so there's still plenty
> >of room to calculate decent limiting resistors for this (200 ohms
> >gives you roughly 50mA here, for instance). So it's a puzzle as to
> >why somebody would need to boost the voltage. Normally, all that
> >matters is that you're a certain amount above the forward voltage
> >drop of the diode.
> >
> >May I take a guess? Betcha these aren't for LEDs. Switch mode
> >regulators are quite similar to the inverters used to power EL light
> >strips, and I've seen a few mentions of those mentioned recently.
> >They require AC to excite them, usually at anywhere from 100-400
> >volts, so it's definitely a "step up" application. Also, I looked at
> >RST's site, at Jim Weir's articles, and it looks like his "mother of
> >all lamp dimmers" was designed for lamps, not LEDs (although it could
> >certainly handle both, to an extent).
> >
> >There are some advantages to both designs, but gosh, look at all the
> >parts. =) With LEDs drawing as little power as they do, it's probably
> >overkill. (That's a hypocritical statement for anybody who's seen my
> >glass cockpit design, but what the hey. <grin>)
> >
> >Regards,
> >Chad
> >
> >
> >
> >
>
>
> advertising on the Matronics Forums.
> ====
>
>
>
>
>
Message 19
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--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <bob.nuckolls@cox.net>
At 08:35 PM 10/21/2003 +0100, you wrote:
>--> AeroElectric-List message posted by: "Steve Sampson"
><SSampson.SLN21@london.edu>
>
>Why do contactors normally have one side labelled to the battery and the
>other to the load? They would appear to be a symmetrical device from the
>internal diagram in Bob's book.
some but not all contactors have one side of coil connected
internally to the BAT terminal. Often, a manufacturer uses
the same shell for all versions of the contactor and one of
the fat terminals gets marked BAT even tho it's really significant
for only part of the product line.
>The reason for the question is that I am wiring up the firewall of an RV9a
>and am using basically diags Z9 and Z24 (to control an internally regulated
>alternator). Placement of the contactor to kill the supply from the
>alternator means the wiring would be simpler if the device was wired
>'backwards'. In fact the current will also flow through it backwards in that
>if a contactor is normally handling current flowing from a battery to
>devices this contactor will be handling current flowing from an alternator
>to a battery.
If you're using a 4-terminal device, you can ignore any
marking suggesting one of the fat terminals goes to
BAT.
>The specific units concerned are the VANS Master Relay and the VANS ND 60
>amp alternator.
As I recall, Van's master relay is a 3-terminal device with one
coil lead attached to BAT. This contactor can't be used for
alternator disconnect, you need a 4-terminal device like
the S701-1 offered by B&C at:
http://www.bandc.biz/S701-1.html
and others.
Bob . . .
Message 20
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--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <bob.nuckolls@cox.net>
At 06:16 PM 10/22/2003 -0400, you wrote:
>--> AeroElectric-List message posted by: dschaefer1@kc.rr.com
>
>Bob ... can you remind me why there are so many diodes on the various
>contactors? I'm building the 'all electric' airplane and don't really know
>why they are there.
>
>Regards,
>
>David
See http://www.aeroelectric.com/articles/spikecatcher.pdf
The S701-1 contactor from B&C is fitted with a single spike
catcher as shown at:
http://www.bandc.biz/S701-1.html
The S701-2 contactor is for crossfeed service and needs
two additional diodes for steering power from either hot
bus to the close the contactor. Hence it has three total as
seen at:
http://www.bandc.biz/S701-2.html
Bob . . .
Message 21
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10/22/2003 08:01:35 PM
--> AeroElectric-List message posted by: caspainhower@aep.com
If you can get by with a limited # of light levels, an option is to have
multiple strings of LEDS that can be switched on separately to provide
different levels of illumination. It would be fairly easy to use op amps
to drive them and use a potentiometer to vary the voltage to the op amp
inputs. A small mechanical ganged switch would probably do the same
thing. A simpler arrangement and built in redundancy.
Craig S.
601 XL
This e-mail message and all attachments transmitted with it from the
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contact the sender by reply e-mail and destroy all copies of the original
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Message 22
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| Subject: | Microair 706 and Audio Iso Amp |
--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <bob.nuckolls@cox.net>
>Comments/Questions: I have built your Audio Iso Amp and installed with a
>Microair 760.
>On initial power-up, the only sound from the audio was an exremely
>"clipped" output. Fearing a major error, I unplugged the Amp and
>jumpered out the audio output from the radio to the audio out pins
>on the Amp harness d-dub (to bypass the Amp) and the radio worked normally
>for about 10 brief test sessions. Then the radio began behaving
>badly- activation of any switch on the radio executes a channel flip-
>flop instead of a normal function. I contacted Microair and they suspect
>a bad processor and are sending a replacement. Three questions please:
>1. Could an error on the Iso Amp damage the radio?
Not likely especially if you put it together with one of our
etched circuit boards.
>2. Is there a way to test the Amp for errors? If you can do this I would
>gladly make appropriate compensation. I believe it to be properly built,
>but did have to correct the pin assignments from what the drawing shows
>(I contacted you regarding this when I assembled the amp)
You can send it to me and I'll test it.
>3. Regarding the recent A-list discussion on dimmers- I built and
>installed a
>PWM dimmer from a kit to control my panel LEDs (almost 1.5 amps worth) I
>do not
>know what frequency it operates at, but works well and did not seem to inject
>noise into the audio while it WAS working- could this perhaps have
>affected the
>radio processor somehow?
Don't think so.
>Sorry to take up so much of your time, but the dragon is winning here...
Awww . . . he's just an especially feisty one . . . they can
all be whipped . . .
Is Microair sending you an exchange radio?
Bob . . .
Message 23
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| Subject: | Updated instructions for Audio Iso Amp |
--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <bob.nuckolls@cox.net>
I've combed out some errors and added a note (14) to
point out connector pin variations depending on how
the connector is mounted. Download:
http://www.aeroelectric.com/Catalog/AEC/9009/9009-700D.pdf
Bob . . .
--------------------------------------------
( Knowing about a thing is different than )
( understanding it. One can know a lot )
( and still understand nothing. )
( C.F. Kettering )
--------------------------------------------
Message 24
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| Subject: | Fuel Pump Popping OV CB |
--> AeroElectric-List message posted by: "Jon Finley" <jon@finleyweb.net>
Hi Bob,
I discussed this problem with you at the Field of Dreams fly-in in
Sullivan, MO a few weeks back. Now that we're not standing on the
tarmac, could you restate your suggestion?
The situation is this: I have a Subaru EJ-22 Legacy engine with fuel
injection. I have most everything wired up per your book. The problem
is that the Alternator circuit breaker pops (OV crowbar installed) when
I switch OFF the auxiliary fuel pressure pump. I temporarily hooked up
a digital meter and "caused" the problem a few times but nothing helpful
was picked up (not surprisingly).
I believe your suggestion was to install a TVS between the fuel pump and
it's switch, correct? It seems like you mentioned a capacitor, does
this ring a bell?
Thanks for all your help!
Jon Finley
N90MG Q2 - Subaru EJ-22 DD - 461 Hrs. TT
Apple Valley, Minnesota
http://www.FinleyWeb.net/default.asp?id=96
Message 25
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| Subject: | Watsonville Seminar Nov 8/9 |
--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <bob.nuckolls@cox.net>
The Watsonville program is a go. Dee and I will be hauling
out of ICT Friday morning of the 7th and hope to see a bunch
of you there!
Bob . . .
--------------------------------------------
( Knowing about a thing is different than )
( understanding it. One can know a lot )
( and still understand nothing. )
( C.F. Kettering )
--------------------------------------------
Message 26
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| Subject: | Re: Updated instructions for Audio Iso Amp |
--> AeroElectric-List message posted by: "J. Oberst" <joberst@cox-internet.com>
Bob, I have a Garmin GMA340 audio panel, and I have installed some mini
earphone jacks that go to its music input. Problem is with portable tape or
CD players, their output level is far short of what's needed to hear them in
the headphones. Garmin has a fix that provides 10dB gain, but that doesn't
seem to me like it will be enough, so I don't want to start removing surface
mount resistors to do it. What would be simplest would be to add a stereo
audio amplifier between my panel jacks and the Garmin music input.
I saw this post on an audio isolation amplifier, and was wondering if this
is what I need. Or if not, has there been a design (or a simple box I can
buy) discussed before?
Thanks.
Jim Oberst
----- Original Message -----
From: "Robert L. Nuckolls, III" <bob.nuckolls@cox.net>
Subject: AeroElectric-List: Updated instructions for Audio Iso Amp
> --> AeroElectric-List message posted by: "Robert L. Nuckolls, III"
<bob.nuckolls@cox.net>
>
> I've combed out some errors and added a note (14) to
> point out connector pin variations depending on how
> the connector is mounted. Download:
>
> http://www.aeroelectric.com/Catalog/AEC/9009/9009-700D.pdf
>
> Bob . . .
>
> --------------------------------------------
> ( Knowing about a thing is different than )
> ( understanding it. One can know a lot )
> ( and still understand nothing. )
> ( C.F. Kettering )
> --------------------------------------------
>
>
Message 27
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| Subject: | Re: Fuel Pump Popping OV CB |
--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <bob.nuckolls@cox.net>
At 08:13 PM 10/22/2003 -0500, you wrote:
>--> AeroElectric-List message posted by: "Jon Finley" <jon@finleyweb.net>
>
>Hi Bob,
>
>I discussed this problem with you at the Field of Dreams fly-in in
>Sullivan, MO a few weeks back. Now that we're not standing on the
>tarmac, could you restate your suggestion?
>
>The situation is this: I have a Subaru EJ-22 Legacy engine with fuel
>injection. I have most everything wired up per your book. The problem
>is that the Alternator circuit breaker pops (OV crowbar installed) when
>I switch OFF the auxiliary fuel pressure pump. I temporarily hooked up
>a digital meter and "caused" the problem a few times but nothing helpful
>was picked up (not surprisingly).
>
>I believe your suggestion was to install a TVS between the fuel pump and
>it's switch, correct? It seems like you mentioned a capacitor, does
>this ring a bell?
>
>Thanks for all your help!
Send me your mailing address and I'll ship you
some parts to try.
Bob . . .
Message 28
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| Subject: | Re: Updated instructions for Audio Iso Amp |
--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <bob.nuckolls@cox.net>
At 09:24 PM 10/22/2003 -0500, you wrote:
>--> AeroElectric-List message posted by: "J. Oberst"
><joberst@cox-internet.com>
>
>Bob, I have a Garmin GMA340 audio panel, and I have installed some mini
>earphone jacks that go to its music input. Problem is with portable tape or
>CD players, their output level is far short of what's needed to hear them in
>the headphones. Garmin has a fix that provides 10dB gain, but that doesn't
>seem to me like it will be enough, so I don't want to start removing surface
>mount resistors to do it. What would be simplest would be to add a stereo
>audio amplifier between my panel jacks and the Garmin music input.
>
>I saw this post on an audio isolation amplifier, and was wondering if this
>is what I need. Or if not, has there been a design (or a simple box I can
>buy) discussed before?
The audio iso amp as configured has a voltage gain of about 1.0
but it could be higher. Is the music input mono or stereo? Do you
have a specification for the input sensitivity of this port? In the
automotive world, aux inputs are on the order of 500 mv rms (1.5v pk-pk)
which is in the same ballpark as headset outputs. I'm a bit mystified
as to why you're having problems.
Bob . . .
Message 29
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| Subject: | Alternator Noise in Headset - Epilogue? |
--> AeroElectric-List message posted by: Pete Waters <pedroagua@yahoo.com>
Bob,
If the weather cooperates, I'll even bring the RV-4 we've been discussing on
the Aerolelectric list.
BTW, I replaced the voltage regulator I had with an automotive one (a Transpo),
and I no longer hear the Morse Code-like noise. The new VR cost me about
$20. I also took the alternator and old regulator out of the airplane to an automotive
alternator shop. They found nothing wrong with either, but at least
in the process I learned that the alternator, which is still in great shape,
is a 35 A Nippondenso model off a mid-70's Honda. The old voltage regulator
is probably of the same vintage, but is completely unmarked and therefore a complete
mystery part. For $20 it was worth it for me to just replace the VR so
that I could write a model and part number on the massive airplane configuration
spreadsheet I'm gradually constructing. I also replace the automotive voltmeter
that came in the airplane with an Electronics Instruments VA-1A volt/ammeter
so I could have an ammeter in the plane to diagnose any future electrical
issues. Right off, I learned that, with both lan
ding
lights off, I pull about 13 A with everything else on; with both landing lights
on, I pull 31 A (off a 35A alternator) and get a flickering discharge light
on the ammeter. So, I clearly need to either (a) go to lower-wattage landing
lights, or (b) disconnect one of them, (c) live with it for the short period
on final when everything is one, or (d) get a higher-output alternator. I'll
probably go for (a) in the short term and (d) at the next annual.
I'm not sure if the headset noise won't return, but at least I'm learning how
this plane is wired.
I'll copy this to the Aeroelectric list also to share it with the bubbas.
Thanks for all the help,
Pete Waters
See you in Watsonville, by plane if VFR, by car if not
---------------------------------
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| Subject: | Re: Updated instructions for Audio Iso Amp |
10/23/2003 12:39:44 AM
--> AeroElectric-List message posted by: caspainhower@aep.com
>Problem is with portable tape or
>CD players, their output level is far short of what's needed to hear them
in
>the headphones.
This might seem obvious but make sure you use the headphone output and not
the line out. I have the same problem I hook up to the line output of the
portable CD player in my Skyhawk. It take about 30 - 50% volumn adjustment
to achieve a comfortable level in the headsets.
Craig S.
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