# Magnetic Curiosity



## Naptowneng (Jun 14, 2010)

I recently installed a simple sound card triggered by a magnetic reed switch. I chose to install it in a track side shed I had made. The card, battery and switch fit nicely. I put the speaker in a nearby building and was ready to go. I installed the reed switch on a curve that comes just before the town siding and station. I adhered magnets on the fromt of my shay and an annie. Had to position them a few times to compensate for the motion of the front of the loco as it rounded the curve.

After running all day, with the sound working nicely, I put the steam locos away and decided to run my Aristo RDC. Lo and behold, when it rolled over the reed switch, it triggered the sound unit. Well that will not do, as it is a steam whistle sound. That is what the on-off switch is for, I suppose.

So now I am pondering if the magnetic field from the Aristo motor block is of sufficient density to trigger a reed switch? Hmm. Or what else could it be? I guess I could try to find an RDC sound, but was wondering if anyone else had run across this effect?

Thanks

Jerry


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## D-n-H - Kirkville Branch (Jan 14, 2008)

well there are magnets in the motor, you could try moving the reed switch to the outside of the rail as far away from center as possible, then move the magnets on the steam locos to match, might help 

could you post details on the simple sound card / trigger switch you installed, bought or built? 

pictures also help


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## East Broad Top (Dec 29, 2007)

It can be, yes. I'm running into that while researching my upcoming GR series on automation. If the motor is particularly low to the ground, with strong enough magnets, and the reed switch sensitive enough, the motor passing overhead can trigger it. It's rare that I'm getting it, but I do get it. 

The solution - dump the dismal and stick to steam.  Okay, seriously, depending on the reed switch, you can sometimes just rotate it a few degrees and it's enough to cure it. 

Later, 

K


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## Greg Elmassian (Jan 3, 2008)

Shield the motors with mu-metal. Google mu-metal, you can probably get a small amount. 

Greg


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## Naptowneng (Jun 14, 2010)

D-n-H:

The sound card I am using comes from Ram Track, a company in Fl that has numerous sound and lighting related products

http://ramrcandramtrack.com/

They supply numerous small sound cards with one sound, complete with speaker switch, reed switch, and magnet

http://ramrcandramtrack.com/rtsound.html

Jerry


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## Dan Pierce (Jan 2, 2008)

Place the reed switch lower on the track and use a stronger magnet to trigger it. 

I get strong magnets from old laptop disk drives and fit them under the cow catcher on steam engines. These must be kept away from motors as you do not want to take a chance of them de magnetizing a motor magnet, or interfering with a motors magnetic flux.


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## Brandon (Jul 6, 2011)

If you want to do some electronics work, get an rfid reader and a picaxe... I'm using rfid since it offers an endless amount of unique triggers vs reed. Also with my railroad automation I have a full computer (raspberry-pi) I'm putting in each locomotive that does extra stuff like a camera in the cabs and AI software running in each loco, overkill for most people but it's fun for me.


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## Brandon (Jul 6, 2011)

Here's a link to how to connect a $10 rfid reader to a picaxe: http://www.picaxeforum.co.uk/showthread.php?20044-Cheap-Chinese-125khz-RFID-reader-Picaxed&s=46dd6d0629178ce42332ad163a6528a6 I also have one of these models of rfid readers and it picks up rfid tags under brass, aluminium, and SS track that I have if the antenna is mounted on the underside belly of a locomotive or flat car (about 1"-2" range depending on the rfid tag type under the track.


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## krs (Feb 29, 2008)

Posted By Greg Elmassian on 28 May 2012 10:53 PM 
Shield the motors with mu-metal. Google mu-metal, you can probably get a small amount.

I would have suggested a shield as well.
Seems the most robust solution at reasonable cost.

Knut


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## Greg Elmassian (Jan 3, 2008)

You could also shield with a thin sheet of sheet steel, but it will take more and not shield as much. The MU metal is also usually more flexible. 

Greg


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## Dan Pierce (Jan 2, 2008)

RFID would be great indoors, but in the outdoors I would worry about dirt/debris causing it to not work without some cleaning, and when you least expect it!! 

A magnet and reed sounds better to me.


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## Greg Elmassian (Jan 3, 2008)

Huh? RFID is radio waves, unaffected by dirt, debris, dust, etc. 

Maybe you were thinking bar codes? 

Could not get much more reliable... overkill for this situation, but definitely reliable and tolerates hostile environments... much better than a mechanical / magnetic reed switch, which is ALREADY having issues, i.e. the reason for this thread. 

Greg


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## toddalin (Jan 4, 2008)

I don't know that anyone has mentioned it, but if possible, you may be able to solve the problem by just turning your reed switch 90 degrees and maybe moving it to one side or the other a bit within the track spacing. Alternatively, you may be able to rotate the "tube" to reorient the contact "leaves" a bit to alleviate the problem.


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## Dan Pierce (Jan 2, 2008)

Yes, I was thinking infra red.


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## Naptowneng (Jun 14, 2010)

Thanks to all for the thoughtful responses. It seems the placement of the reed switch is a bit of an art so I have been experimenting with a blob of putty to hold switch in the gauge. Testing rotation of switch tube also. Still learning.

Jerry


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## toddalin (Jan 4, 2008)

Posted By Naptowneng on 19 Jun 2012 05:50 AM 
Thanks to all for the thoughtful responses. It seems the placement of the reed switch is a bit of an art so I have been experimenting with a blob of putty to hold switch in the gauge. Testing rotation of switch tube also. Still learning.

Jerry




I like simple solutions that accomplish the goal. I guess I have a simple mind. As Einstein noted,
"Everything should be made as simple as possible, but not simpler."


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