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LED flags

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rd2(at)evenlink.com
Guest

Posted: Mon Jul 17, 2006 7:34 am Post subject: LED flags

I am considering adding LEDs to indicate which source signal is used by the

autopilot (S-Tec System 50). A rotary switch will select between 3 sources

(NAV/GS, NAV2, GPS). It might be a good idea to also use the same LEDs as

flags for the source in use (not just which source was selected but also if

the source is on/working). Sure, the indicators already have flags but it

is logical to have flags where the source selector is located. 

I am using 2 KX-155s and KI 208/KI 209 indicators.



Has anyone done this? What signal are you using to make the LEDs act like

flags?



Thanks

Rumen

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brian

Joined: 02 Jan 2006
Posts: 643
Location: Sacramento, California, USA

Posted: Mon Jul 17, 2006 2:44 pm Post subject: LED flags

On Jul 17, 2006, at 11:16 AM, rd2(at)evenlink.com wrote:



 	  Quote: 	
		   



 I am considering adding LEDs to indicate which source signal is  

 used by the

 autopilot (S-Tec System 50). A rotary switch will select between 3  

 sources

 (NAV/GS, NAV2, GPS). It might be a good idea to also use the same  

 LEDs as

 flags for the source in use (not just which source was selected but  

 also if

 the source is on/working). Sure, the indicators already have flags  

 but it

 is logical to have flags where the source selector is located.

 I am using 2 KX-155s and KI 208/KI 209 indicators.



 Has anyone done this? What signal are you using to make the LEDs  

 act like

 flags?


	


A standard ARINC "flag" signal is a low-current bipolar (+/-) current  

designed to drive a standard "flag" which is actually a meter  

movement. The meter movement has a specific DC resistance (about 300  

ohms as I recall) and the radio is supposed to source about 2mA to  

flip the flag. (I am probably wrong about the exact number as I am  

working from memory but I am in the ballpark.) The current is either  

positive or negative depending on the sense of the flag. (BTW, the  

flag resistances and currents are the same as for the CDI if I recall  

correctly.)



Your GPS probably has a Nav Super Flag output. Basically this is a  

generic good/bad signal and is probably what you want for this case.  

Check your GPS's manual for the behavior of the Nav super flag for  

your GPS. You can probably drive a LED directly with this signal.



The KX-155 is a bit more difficult. The VOR/LOC nav converter is in  

the KI-208 or KI-209, not in the radio. You will have to steal the  

signal from the indicator. I know the KI-208 or KI-209 have CDI  

outputs but do they have flag outputs? (I don't recall -- it has been  

a really long time since I have messed with those indicators.)



My guess is that you are going to have to cook up an amplifier  

circuit to drive the LED without loading the flag driver circuit too  

much.



Brian Lloyd                         361 Catterline Way

brian-yak AT lloyd DOT com          Folsom, CA 95630

+1.916.367.2131 (voice)             +1.270.912.0788 (fax)



I fly because it releases my mind from the tyranny of petty things . . .

— Antoine de Saint-Exupéry

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Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

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_________________
Brian Lloyd
brian-yak at lloyd dot com
+1.916.367.2131 (voice) +1.270.912.0788 (fax)

I fly because it releases my mind from the tyranny of petty things . . .
- Antoine de Saint-Exupery

rd2(at)evenlink.com
Guest

Posted: Mon Jul 17, 2006 3:55 pm Post subject: LED flags

Brian, thanks



 	  Quote: 	
		  

I know the KI-208 or KI-209 have CDI outputs but do they have flag outputs?
	


 	  Quote: 	
		  

Not to my knowledge. This may not be easy to solve. 
	




The GS flag ouput comes from the KX155 (if I recall correctly). It could be

spliced into a hi-impedance amp for the led.



The GPS is the lesser problem to tackle.



Rumen

do not archive



_____________________Original message __________________________

                  (received from Brian Lloyd; Date: 06:38 PM 7/17/2006

-0400)

________________________________________________________________


On Jul 17, 2006, at 11:16 AM, rd2(at)evenlink.com wrote:



 	  Quote: 	
		   



 I am considering adding LEDs to indicate which source signal is  

 used by the

 autopilot (S-Tec System 50). A rotary switch will select between 3  

 sources

 (NAV/GS, NAV2, GPS). It might be a good idea to also use the same  

 LEDs as

 flags for the source in use (not just which source was selected but  

 also if

 the source is on/working). Sure, the indicators already have flags  

 but it

 is logical to have flags where the source selector is located.

 I am using 2 KX-155s and KI 208/KI 209 indicators.



 Has anyone done this? What signal are you using to make the LEDs  

 act like

 flags?


	


A standard ARINC "flag" signal is a low-current bipolar (+/-) current  

designed to drive a standard "flag" which is actually a meter  

movement. The meter movement has a specific DC resistance (about 300  

ohms as I recall) and the radio is supposed to source about 2mA to  

flip the flag. (I am probably wrong about the exact number as I am  

working from memory but I am in the ballpark.) The current is either  

positive or negative depending on the sense of the flag. (BTW, the  

flag resistances and currents are the same as for the CDI if I recall  

correctly.)



Your GPS probably has a Nav Super Flag output. Basically this is a  

generic good/bad signal and is probably what you want for this case.  

Check your GPS's manual for the behavior of the Nav super flag for  

your GPS. You can probably drive a LED directly with this signal.



The KX-155 is a bit more difficult. The VOR/LOC nav converter is in  

the KI-208 or KI-209, not in the radio. You will have to steal the  

signal from the indicator. I know the KI-208 or KI-209 have CDI  

outputs but do they have flag outputs? (I don't recall -- it has been  

a really long time since I have messed with those indicators.)



My guess is that you are going to have to cook up an amplifier  

circuit to drive the LED without loading the flag driver circuit too  

much.



Brian Lloyd                         361 Catterline Way

brian-yak AT lloyd DOT com          Folsom, CA 95630

+1.916.367.2131 (voice)             +1.270.912.0788 (fax)

- The Matronics AeroElectric-List Email Forum -

Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

http://www.matronics.com/Navigator?AeroElectric-List

brian

Joined: 02 Jan 2006
Posts: 643
Location: Sacramento, California, USA

Posted: Mon Jul 17, 2006 6:22 pm Post subject: LED flags

On Jul 17, 2006, at 7:38 PM, rd2(at)evenlink.com wrote:

 	  Quote: 	

 Brian, thanks

>

 I know the KI-208 or KI-209 have CDI outputs but do they have flag  

 outputs?

>

 Not to my knowledge. This may not be easy to solve.

No. That would involve hacking the guts of the KI-209. I wouldn't do  

that if it were mine.

BTW, the KX-165 has an internal VOR/LOC converter which is why it is  

usually used for driving an HSI.

Nowadays you want to look for a NAV/COM that outputs the nav info in  

ARINC-429 format. That means that instead of having to have two wires  

for CDI, two wires for VDI, two wires for NAV flag, two wires for GS  

flag, and 5 wires for OBS, you just need a data-out wire, a data-in  

wire, and ground. It sure makes wiring the avionics stack a LOT easier.

 	  Quote: 	

 The GS flag ouput comes from the KX155 (if I recall correctly). It  

 could be

 spliced into a hi-impedance amp for the led.

Yes, the GS receiver in the KX-155 has the converter built in and  

just outputs nav-valid, CDI, and flag.

 	  Quote: 	

 The GPS is the lesser problem to tackle.

Right.

Brian Lloyd                         361 Catterline Way

brian-yak AT lloyd DOT com          Folsom, CA 95630

+1.916.367.2131 (voice)             +1.270.912.0788 (fax)

I fly because it releases my mind from the tyranny of petty things . . .

— Antoine de Saint-Exupéry

- The Matronics AeroElectric-List Email Forum -

Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

http://www.matronics.com/Navigator?AeroElectric-List

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