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Reed Switch / Magnet Problem and Testing

MartySantic

MartySantic

Well Known Member
Received my CARE package today and installed the magnet in the wing pin (not yet expoxied) and the reed switch wired to a DVM. Could not get the reed switch to close after trying a multitude of reed switch positions.

In the fuselage the magnet is vertical and the reed switch is horizontal and is 9/16" from the tip of the reed switch to the magnet centerline.

Removed them and did some bench testing. With the magnet vertical and the reed switch horizontal you have to get them to within 7/16" for the reed switch to work (close) reliably. The pair become more sensitive if you could mount the reed switch vertically. With the magnet AND reed switch vertical, (ie. side by side) they work reliably at 9/16".

Also tried reversing the magnet, did NOT make a difference. Also tried mounting the magnet higher in the tube, it was worse. The reed switch is more sensitive to the magnet ends as opposed to the center of the magnet (with the magnet vertical/reed switch horizontal).

This is MOST definitely a problem and will e-mail Vans.

ANYONE have any better luck??
 
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Reed switch

I tried mounting the switch on top of the armrest. This placed it very close to the tip of the pin and it worked very well. Confirms your results. Doesn't look very good tho.
 
reed switch

Marty,
I have had experience with magnetic reed switches in industrial applications. In most installations the magnet and reed switch are parallel with each other with the magnet centered on the switch. That position works the best as you found in your testing. Polarity of the magnet does not matter. There is a magnetic circuit that leaves one pole of the magnet, travels through the air to one end of the switch, through the ferrous metal of one half of the switch, across a gap to the other half of the switch, and finally through the air again to the other pole of the magnet. I do not have my finish kit yet and am not familiar with the installation on the RV-12. But for proper operation, the magnet and switch will work the best if they are parallel and in close proximity with each other. If the magnet and switch can not be mounted parallel, then perhaps the magnetic circuit can be completed by providing another path in order to minimize the distance that the magnetic lines of force must travel through the air. This alternate path can be made using steel sheet metal. A lamination from an old door bell transformer would be ideal. If Van's did not design the mounting to be fool proof and trouble free, then builders are going to bypass the switch. Doing so could result in forgetting to lock the wings in place.
I hope this helps. Joe
 
Hey guys I spent most of the day with these. After bench testing . I found that the steel tube that the slider and magenet set in is to long. Its interfears with magenet/switch. Hear is what I did and it worked great. I cut 1/2 inch off of the tube so that the slider is exposed directly to the switch with out any steel between it(the switch) and the magnet. I also enlarged the hole so that the switch come thru the arm rest and touches the aluminium slider. Its activates now when it gets within 1/2 ti 3/4 of an inch of the slider. Hope this makes sense . I have a hard time putiing on words what I did. I mounted just as per plans. I just made it so the reed switch is closer to the magenet and made sure there is no steel between the magnet and switch.

If you bench test you will find that the switch has a hard time activating when the magnet is shielded by the steel tube.

After testing several times it works without fail every time.

Brad
 
I like your thinking on this, Brad. I'm going to do the same thing. Us old guys need that red light on the panel to be functional, to remind us, if we forget to put the pins in! Steve
 
Cutting tube

Cutting the tube shorter might disqualify the aircraft from being registered as E-LSA. Van's should make the tube out of non-magnetic stainless steel so that it will not short-circuit the magnetic lines of force.
Here is a suggestion for someone who likes to experiment: Cut a rectangular piece of sheet metal 1/2" x 2" from the top of a tin can and drill a hole in one end. Mount it on top of F-1248B using the same 10x32 screw that holds the MS21919DG4 clamp for the reed switch. Position the other end of the sheet metal over the WD-1217C pin.
I do not have the Finish Kit yet, so I can not try it. I downloaded page 31-06 from Van's website to help me understand what you guys are talking about. Assuming that WD-1217C is the magnet, then the piece of ferrous sheet metal will help concentrate the magnetic lines of force through the reed switch.
Joe
 
Newer revision

Scott,
Thanks for letting us know that cutting the WD-1217 is allowed, at least on the original plans. Page 31-06 Revision 1 does not mention it.
Joe
 
Mich is right

The parallel mounting of the reed switch and magnet in the pin *is* the answer. Using the same hardware, I just drilled 3/16 into the vertical flange of the armrest and mounted the reed switch vertically behind the flange. Makes a good contact every time. Installation is not as elegant as the original but much better than the top-o'-the-armrest solution which was the only way I could get it to work heretofore. I'll put a dab of RTV on the south end of the switch before first flight so a not-so-perfect landing won't pull it out of the Adel clamp.
 
The hard part

N223JH,
Good going getting the reed switch to work. The hard part is getting it to work only when the magnet is in the hole, and making sure that it does not work when near the hole but not actually latched.
Joe
 
Fer sure, fer sure. Ohm meter goes to zero only after the pin pops all the way into the hole. Don't need any false positives on wing attach! J
 
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