Today's Message Index:
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1. 06:06 AM - Re: LED Ghosting (Robert L. Nuckolls, III)
2. 08:46 AM - Re: LED Ghosting (donjohnston)
3. 12:43 PM - Re: LED Ghosting (donjohnston)
4. 06:02 PM - Re: Re: LED Ghosting (Robert L. Nuckolls, III)
Message 1
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| Subject: | Re: LED Ghosting |
At 12:57 PM 6/15/2014, you wrote:
>
>I've built a Master Warning Panel using LEDs for things like boost
>pump on, starter engaged, pitot heat on, etc. I'm using Eric's
>EGRAVR dimmer to control the brightness. Everything works great.
>
>http://www.velocity-xl.com/blog/wp-content/uploads/2013/08/2013-08-14-IMG_20130814_191418_518.jpg
>
>Except the engine analyzer (low oil pressure) alarm.
>
>That line is supposed to go to ground when an alarm condition
>occurs. But the LED for that warning is always slightly lit. The
>engine analyzer people said it was designed for incandescent and to
>put a 1.5k resistor across the LED.
Wrong place for the resistor. There is a resistor X in
series with the LED to bias it up to run on the
14V supply. Resistor Z is used to make the diode/X
string emulate an incandescent bulb. Try 1000 ohms
at Z.
Emacs!
Bob . . .
Message 2
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| Subject: | Re: LED Ghosting |
nuckolls.bob(at)aeroelect wrote:
>
> Wrong place for the resistor. There is a resistor X in
> series with the LED to bias it up to run on the
> 14V supply. Resistor Z is used to make the diode/X
> string emulate an incandescent bulb. Try 1000 ohms
> at Z.
>
> [img]cid:7.1.0.9.0.20140616075849.01f3d938@aeroelectric.com.0[/img]
>
>
>
> Bob . . .
Well that would make my life a gazillion times easier!
It makes sense too. I'll give it a try.
Thanks!
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=424936#424936
Message 3
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| Subject: | Re: LED Ghosting |
Sadly, it did not help. It does eliminate the ghosting. But just like when I
put the resistor across the LED, it still results in a dimmer LED overall.
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=424951#424951
Message 4
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| Subject: | Re: LED Ghosting |
At 02:41 PM 6/16/2014, you wrote:
>
>Sadly, it did not help. It does eliminate the ghosting. But just
>like when I put the resistor across the LED, it still results in a
>dimmer LED overall.
Okay, was this 'output' intended to drive
an incandescent lamp in the first place?
The symptoms you describe suggest that it's
an LED specific output and may have a resistor
already built into the output.
Bob . . .
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