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nuckolls.bob(at)aeroelect
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 Posted: Tue Aug 19, 2014 4:43 am Post subject: Dynon D-180 & flickering LEDs |
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At 09:51 PM 8/18/2014, you wrote:
--> AeroElectric-List message posted by: "user9253" <fransew(at)gmail.com>
I have been corresponding with a RV-12 owner in TX. His Dynon D-180 has a problem with LEDs that flicker when they should be on steady. The D-180 supplies negative PWM voltage to LEDs which are external to the D-180. Download the D-180 Installation Manual http://www.dynonavionics.com/downloads/Install_Guides/FlightDEK-D180_Installation_Guide_Rev_H.pdf
and read about "External EMS Warning Light" on page 4-10. The aircraft owner did some experiments. Here are the results:
With the engine off and the D-180 powered by the aircraft battery, the LEDs are on steady. With the engine running, the LEDs flicker. With the engine still running, if the avionics switch is shut off, the D-180 reverts to its internal backup battery and the LEDs illuminate steadily. Engine still running and the avionics switch is turned back on, the LEDs flicker again. This experiment was repeated and the results are consistent. From these experiments I conclude that the D-180 puts out a steady PWM voltage when operating on battery power (whether aircraft battery or internal backup battery). And when operating off the alternator, the D-180 puts out an intermittent PWM voltage which causes LED flicker.
Do I presume correctly that he has gone through the set up screen for managing the output of this pin?
To configure EMS DB37 Pin 29 as an external warning light, enter the EMS menu by pressing any button beneath an EMS main page. Press MORE > SETUP > GLOBAL. Press DOWN. to select ALARM CONFIG and press SEL. LGT BHVR: ACK SOLID configures the external alarm light to remain on (solid) when the alarm condition is acknowledged. LGT BHVR: ACK CLEAR configures the external alarm light to go off when the alarm condition is acknowledged. The word 'flicker' implies a visible, random modulation of the light output. If this output is being deliberately PWM for the purpose of controlling apparent intensity, the PWM frequency will be too high for the eye to perceive anything like a 'flicker' . . . it seems unlikely that the difficulty is a function of any normal behaviors designed into the D-180.
With the engine running, the D-180 indicates a system voltage of 13.7 which is normal for RV-12s. All E-LSA RV-12s have a 22,000 microfarad capacitor connected to the output of the Rotax rectifier/regualtor. If that capacitor is bad, could that cause the D-180 to output an unsteady PWM voltage to the the LEDs? Or should the D-180 be able to function even if the aircraft electrical power is dirty and not pure DC?
If you put a 'scope on the bus of any airplane with the alternator running you will find that it's anything but "pure DC". Mil-Std-704/DO-160 design and qualification recommendations advise system integrators to consider this in the design of bus-powered products. Dynon is no less aware of this than anyone else . . . and based on my conversations with them, perhaps more so.
The legacy 22,000 uF capacitor installation on PM alternators is of limited utility for smoothing the output from PM alternator rectifier/regulators. Peek at the bus with a 'scope and do a capacitor-connected/disconnected comparison for confirmation. A casual observation with a 'scope will not produce much confidence that the capacitor is doing anything useful in the time domain.
See: http://tinyurl.com/n5yd3vw
Some day I may get the chance to put a spectrum analyzer on the bus and get some details for benefits in the frequency domain . . . but I don't expect to see anything that would alter the way we do system integration under 704/160 design goals.
I suggest that he experiment with an incandescent lamp wired to this output and powered from a couple of lantern batteries or line operated bench supply. Then hook the lamp to the bus for power to see if behavior changes. He could also consider talking to the folks who designed and built the system. They're very amiable folks (at least they were the last time I talked with them perhaps 4 years ago). They're going to know more about their system than anyone you're going to find on this List . . . or in-the-wild.
Bob . . . [quote][b]
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user9253
Joined: 28 Mar 2008
Posts: 1921
Location: Riley TWP Michigan
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| Posted: Wed Aug 20, 2014 6:34 am Post subject: Re: Dynon D-180 & flickering LEDs |
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| Quote: | | Do I presume correctly that he has gone through the set up screen for managing the output of this pin? |
Yes, but even if set up incorrectly, I would not expect differing behavior depending on power source to the D-180.
Bob, I gather from your response that it is highly unlikely that a faulty 22,000 microfarad capacitor is causing the flickering LEDs. You also said that it is unlikely that the difficulty is a function of any normal behaviors designed into the D-180. The question that only Dynon can answer is, is there a D-180 failure mode that can cause the dimmer output to flicker?
The problem with me trying to help someone halfway across the country is that I can not actually see the symptoms. And any tests that I suggest might not be fully understood or the results correctly interpreted.
It can be very frustrating for me and for an aircraft owner to not be able to solve their electrical problem. But when I am able to walk someone through troubleshooting and they solve the problem, it is very rewarding to me.
Thanks for the advice, Bob.
Joe
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nuckolls.bob(at)aeroelect
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| Posted: Wed Aug 20, 2014 11:30 am Post subject: Dynon D-180 & flickering LEDs |
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At 09:34 AM 8/20/2014, you wrote:
| Quote: |
> Do I presume correctly that he has gone through the set up screen
for managing the output of this pin?
Yes, but even if set up incorrectly, I would not expect differing
behavior depending on power source to the D-180.
|
wasn't sure if there was a mode where the light was
expected to flash . . . as opposed to 'flicker' . . .
| Quote: | Bob, I gather from your response that it is highly unlikely that
a faulty 22,000 microfarad capacitor is causing the flickering
LEDs. You also said that it is unlikely that the difficulty is a
function of any normal behaviors designed into the D-180. The
question that only Dynon can answer is, is there a D-180 failure
mode that can cause the dimmer output to flicker?
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agreed. see if the problem goes away with the alternator
off line . . .
| Quote: | The problem with me trying to help someone halfway across the
country is that I can not actually see the symptoms. And any tests
that I suggest might not be fully understood or the results
correctly interpreted.
|
| Quote: | It can be very frustrating for me and for an aircraft owner to
not be able to solve their electrical problem. But when I am able
to walk someone through troubleshooting and they solve the problem,
it is very rewarding to me.
|
understand . . . been working in similar venues for
25 years.
Bob . . .
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user9253
Joined: 28 Mar 2008
Posts: 1921
Location: Riley TWP Michigan
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| Posted: Wed Aug 20, 2014 4:18 pm Post subject: Re: Dynon D-180 & flickering LEDs |
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| Quote: | wasn't sure if there was a mode where the light was
expected to flash . . . as opposed to 'flicker' . . . |
Yes, when an input to the D-180 is out of limits, the D-180 flashes an on-screen warning and also flashes the external LEDs connected to the PWM dimmer pin. However, I asked the RV-12 owner if the LEDs were flashing an alarm or just flickering. He said flickering.
Joe
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Joe Gores |
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nuckolls.bob(at)aeroelect
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| Posted: Wed Aug 20, 2014 4:58 pm Post subject: Dynon D-180 & flickering LEDs |
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At 07:18 PM 8/20/2014, you wrote:
| Quote: |
> wasn't sure if there was a mode where the light was
> expected to flash . . . as opposed to 'flicker' . . .
Yes, when an input to the D-180 is out of limits, the D-180 flashes
an on-screen warning and also flashes the external LEDs connected to
the PWM dimmer pin. However, I asked the RV-12 owner if the LEDs
were flashing an alarm or just flickering. He said flickering.
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Okay, make sure it's not the fixture or power
supplied to the fixture. Do the experiment with
just a light bulb and 12v battery to see that
the D-180 performs as advertised with those
to variables controlled.
Bob . . .
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user9253
Joined: 28 Mar 2008
Posts: 1921
Location: Riley TWP Michigan
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| Posted: Fri Aug 22, 2014 6:26 pm Post subject: Re: Dynon D-180 & flickering LEDs |
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I received the following from the RV-12 owner:
| Quote: | | during Pre-start: LEDs ON steady(with the alarms on the D180 indicated, the LEDs should be blinking until the 1-6 alarms are cancelled) |
From that it seems that the D-180 dimmer output is NOT set up correctly to flash when alarm conditions exist. The RV-12 owner is out of town until Sept 3, so troubleshooting is on hold.
Bob, you may have hit the nail on the head when you asked, "Do I presume correctly that he has gone through the set up screen for managing the output of this pin?"
Joe
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