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Canopy Latched Sensor

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jdubner(at)yahoo.com
Guest

Posted: Sun May 14, 2006 2:10 pm Post subject: Canopy Latched Sensor

 	  Quote: 	
		   I'm not familiar with any specific reflective-type optical sensors

 but I'm guessing that would be the way to go.


	


Following up on my original post here ...



After a couple of weeks of scratching my head, I found the IR HOA0149

Reflective Sensor ($3.36 ea. at DigiKey, see

http://rocky.digikey.com/WebLib/Honeywell%20Sensing%20%26%20Control/Web%20Data/HOA0149.pdf).

I breadboarded a circuit and found that it worked pretty well as long as:

  1) The LED was heavily biased (30 or 40 ma. but not 10 or 20).

  2) The reflective object was a flat surface (unlike the domed head of

the screw I wanted to use).  Even the Phillips slots in the head

diffused the reflective light considerably and reduced the sensitivity.

  3) The reflective object was fairly close to the optimum position as

specified in the data sheet.  There wasn't a lot of in/out, left/right,

or up/down tolerance on positioning the latch handle relative to the

Reflective Sensor.



In order to turn ON a warning light when the latch handle was out of

position (not latched) an inverter was required so I added a resistor

and transistor.  The Reflective Sensor has a poor current transfer ratio

and there is less than one milliampere available to bias the transistor,

sometimes much less depending on position.  In order to reliably control

the #382 light bulb in my Canopy Unlatched indicator I decided I needed

a Darlington-connected configuration.



This is where I pulled the plug.  I decided it was too complicated and

"touchy" for my real-world application and I'd rather be flying.

Soooooo, I went back to a Cherry microswitch <groan>.  Maybe I'll look

at this again in my *next* airplane when I have more freedom in the

mechanical design.



--

Joe



Joe Dubner

Long-EZ 821RP

Lewiston, ID

On 27-Apr-06 09:21 Joe Dubner wrote:

 	  Quote: 	
		   I'm looking for a better way to implement the canopy unlatched warning

 system on a Long-EZ.  The standard method is to use a small microswitch

 that responds to "canopy latched".  (This is not the same as "canopy

 closed", which would be easy enough to implement but I want a "latched"

 indication.)

 

 Here's an illustration of the standard system:

 http://users.lewiston.com/hth/jd/CanopyLockMicroswitch.jpg

 

 When the canopy locking handle is pushed forward (left in the image) far

 enough to latch the canopy locking mechanism, the head of the screw on

 the handle (at the right in the image) fits in the hole on the latch and

 actives the microswitch through its (specially bent) lever.

 

 I'm not happy with the microswitch as it doesn't hold up well under use

 and wonder if any Aeroelectric Connection readers can come up with a

 better idea.  I've searched for optical interrupters but can't find one

 with a gap large enough for the head of the relatively large #10 screw.

  I'm not familiar with any specific reflective-type optical sensors but

 I'm guessing that would be the way to go.

 

 Any ideas?

 

 Thanks,

 Joe

 Long-EZ 821RP

 Lewiston, ID

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brian

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

Posted: Sun May 14, 2006 2:33 pm Post subject: Canopy Latched Sensor

On May 14, 2006, at 3:00 PM, Joe Dubner wrote:

 	  Quote: 	
		  

 This is where I pulled the plug.  I decided it was too complicated and

 "touchy" for my real-world application and I'd rather be flying.

 Soooooo, I went back to a Cherry microswitch <groan>.  Maybe I'll look

 at this again in my *next* airplane when I have more freedom in the

 mechanical design.


	


Sometimes a checklist item is the best solution.

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-Exupry

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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

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