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Reed switches on armrests

D

dinowal

Active Member
Hi Folks, I installed these reed switches today & have encountered my first significant problem of the build. When testing the switches as instructed in step 5 on page 31B-10, there was no continuity ( the reed switch did not close) when the fuselage pin stopper was snapped into the fuselage pin latch. The switches did not close at any time on either side of the aircraft when the stopper was moved about or removed or inserted slowly. I checked the switches with a magnet external to the system & they work (close) OK. So as suggested I removed 1/32 from the WD1217 tube. No Change. I removed a little more, totalling 3/32, & now the switches close as the stopper pin is inserted slowly, but open again as the stopper pin becomes fully engaged (up) in the hole in the latch. It feels as if the reed switches are too low, but they are definitely held in the cushion clamps as in the drawing. I think there was a thread about this problem a long time ago, but I cannot find it; any advice or help from you builders who have gone before would be greatly appreciated, I am out of ideas myself.... Cheers & thanks, DEAN....
 
Dean, I had a lot of trouble getting them to work too. Even ordered new reed switches. Eventually got them adjusted properly but it was a trial and error process. If you haven't already, try bending the tabs on the cushion clamp to adjust the height a bit. If they kind of work now, you are probably not far off.
 
Keep trimming a little at a time off the tubes until the magnet works. Neither of mine worked either but the tubes were a little tall compared to the center of the reed switch hole.
 
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Trim Tube

If the switches work with a magnet then keep triming the tube until they work. Mine were about 3/8 too long to start with. Go slow, measure twice and cut once....
 
I had a **** of a fight with them as well. My problem was finally solved with changing the position slightly of the adel clamps by bending the clamps to change their position. Trimming the tube did no good for me.
After all that fight, I am not even going to use them I don't think, too much trouble to wire them in to my redesigned wiring system, and I would probably notice the wings missing if I tried to fly that way anyhow..
 
Page 31-06

Here is a link to a pdf document that explains how reed switches work:
http://www.digikey.com/Web%20Export/Supplier%20Content/Meder_374/PDF/MEDER_Reedswitch_used_with_permanent_magnet.pdf?redirected=1
Here is a link to an animation showing the operation of a reed switch:
http://reed-switch-info.com/resources/Switch_Magnetic_operate_lightbulb.gif
Just as electrical circuits can have short circuits, so too can magnetic circuits have short circuits. The WD-1217 steel tube short circuits part of the magnetic field. Shortening the tube reduces the magnetic flux going through the steel and allows more to go through the switch.
I think that mounting the reed switch as high as possible will help. Using a clip such as T-1216 on page 37-06 instead of a cushion clamp is worth a try.
Joe Gores
 
The reed switch on my left side was a little cranky. It works sometimes. When it doesn't I use one of those magnets on the end of an extension rod, the ones you use to pick up hard to get to items that were dropped. Just touch it to the tube to activate the switch. The magnet in the tube is strong enough to keep the switch open.
 
thanks

Thanks fellow builders for all that info & links to previous discussions. Seems it is not the most foolproof of systems. I will continue experimenting.... Cheers, DEAN ...
 
Spar Pin Magnetic Field

I also had some issues getting the reed switches to activate using the dimensions in the Van's drawings. I did some testing to determine the issues with the magnetic field and the masking of the SS handle and found that 0.125" can make a big difference in getting the switch to active. I put together a document that shows the magnetic field required to activate the reed switch. The two lessons learned are extending the aluminum pin by 0.125" increases the field's activation distance and make sure the reed switch is ABOVE the end of the SS portion of the Spar Pin handle.

Check out the pdf link below for a visual of the magnetic field: https://www.dropbox.com/s/l32g1pkx1wm2ngt/RV12 Spar Pin Magnetic Map, Oct 2012.pdf

John Salak
RV-12 120116
 
success

Spar interlock pins now working reliably! I enlarged the hole in the side of the armrest just slightly to 5/32, and made clips to hold the reed switches right up against the underside of the armrest as Joe suggested. Eureka! Added just a little Silicone (RTV) to ensure no movement with vibration. Thanks Joe & everyone for your advice, Cheers, DEAN...
 
Dean - Any chance you can post a photo of your reed switch install for us to have a look at?

Joe always has great solutions .. glad to hear his suggestion worked well for you. Think I will try to mount the switch that way from the get go.
 
Hi John, I'll give it a try but may fail the task - it's an awkward place to photograph, & I'm not sure my computer skills are up to getting a photo on to this site... In any case, the clip is a simple piece of Al sheet, approx. 1/2 by 1&1/4 inches, with a hole for the screw & a couple of bends to hold the reed switch flat on a surface. Took only 5 mins to do... Cheers, DEAN....
 
Shot In The Dark

A while ago (2 years??) I got a letter from a UK RV 12 builder who suggested a 'mechanical' electrical wing connection possibility. I lost the letter (working abroad). I believe the builder ran a hotel/restaurant. If he reads this I would be interested in any results he came up with.
Jim D
 
photos

John- G, I have a couple of good shots of my clips, - if someone can educate me on how to upload them I will gladly do so. Otherwise,if you PM me with your email address I can send them that way.... Cheers, DEAN...
 
It's been quite some time since I set the reed switches but I do recall that removing the spring made it easier to find and mark the sweet spot.
 
photo

a try at inserting photo
DSC02254_zpsda3fdf48.jpg
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More success

Wow, I managed to insert a photo.... maybe I'm not such a computer nerd after all!!?? cheers, DEAN....
 
Thanks for that, Dean. Looks like a very neat solution. I'm still struggling with one switch - the other works as advertised after a lot of fiddling.
 
dinowal... Thanks for confirming my suspicions. My reed switch only activates when the steel sleeve is at the bottom of the reed switch, not centered on the reed switch as per the instructions. So I suspect that one can either remove some of the steel sleeve or mount the reed switch as high as possible under the armrest to achieve this relative positioning. The stock mounting clamp seems to mount the reed switch too low to trigger the reed switch.

As an experiment I removed the rubber sleeve from the upper portion of the mounting clamp. I trimmed a portion of the removed rubber sleeve and placed this trimmed piece of rubber under the remaining rubber sleeve on the bottom of the mounting clamp. This maintained the excellent mechanical grip of the mounting clamp on the reed switch and placed the reed switch higher, close to the bottom of the arm rest. If I exercise the magnetic plunger down and up one full cycle, this will trigger the reed switch.

Jeff

Edit: On the left side, I had to remove the full 1/8 inch of steel tubing as allowed in the plans to get the reed switch to trigger, even with the reed switch mounted as close to the underside of the arm rest as possible using the included hardware. On the right side I removed 1/32 of an inch of steel tubing. Getting the tiny snap bushings in place and passing the wires through the snap bushings was not fun.
 
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Switch

I had one that was very difficult. I found a small magnet and placed it on top of the tube. This confirmed the switch worked. I decided to leave it in place since it would not fit through the hole if the pin was removed
 
Replying to the most recent thread. Put my spar pin switches in today. Followed along with the directions (the magnets were glued in a week or so ago) and no joy. Came in - read these threads and saw that others were having trouble. Went back out and over thought the problem and decided to just follow the instructions and took 2 to 3 32nd of the pin arms. Everything worked perfectly. For anyone having problems I would recommend following the instructions taking a 32nd off at a time until it works.
 
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