activating lights with magnets

[corksean12]

Hey all,

Ive heard of people adding circuits to cabooses/passenger cars that activate interior lights when a magnet is waved over them.Does anyone know where I could find a schematic or plans to make this type of circuit? I understand a reed switch is involved but I can't figure out how to keep the lights on AFTER the magnet is no longer present.

Thanks in advance,

Sean 

[jrbernier]

Sean,

  Rapido sells their 'Easy Peasy' lighting set that uses a 'wand' to turn on/off the lights.  If you want to 'roll your own', Curcuitron has magnetic reed switches(Walthers stocks them).

Jim Bernier

[MisterBeasley]

You need what's called a "latching" magnetic reed switch.  A regular switch only closes when the magnet is waved over it, while a latching switch will close and hold its position.

[bobgrosh]

You can make your own latching reed switches. Just use the type that are a glass tube with a lead sticking out each end. Permanently attach one pole of a small bar magnet to one of those leads.

Now a magnet "wand" passed by the reed in one direction will close it, in the other direction it will open it.

If you mount the reed switch on the bottom of the car with the leads parallel to the rails, you can put a magnet in the track with one pole facing up so the car will turn the lights on when leaving a yard and off when entering the yard. You can reverse the behavior by reversing the poles of the magnet in the track.

This would also allow you to use two magnets, one at each end of a tunnel so that one would turn the lights on before you enter the tunnel and another would tun them off when you exit the tunnel. Note that for a single track line, it would work backward from what you want if the train is going the other direction.

 

[cliffsrr]

Thanks Bobgrosh! I have been playing with reed switchs for a while and was glad to see your way of making them latch. This opens up a whole new aspect to what I can do

Cliff

[JoeinPA]

My Thanks also to Bobgrosh ! I tried some breadboard circuits with your reed switch modification and the results were excellent. Thanks for the info.

Joe

[bobgrosh]

Hey.

You guys are more than welcome. I'm glad my description helps.

 You might search some Large scale forums for more hints. They use reed switches for all sorts of things. Almost all LGB sound equipped locos came with two reed switches for the bell and whistle. LGB also had reed switches between the rails to operate turnouts and stuff. Most large scale sound cards use reed switches for chuff. You will find cool tips on those forums for things like making the reeds change states faster and more reliably.

BB

[Dub]

Appreciate the info bobgrosh. Reed switch info is a little lean. I'm doing cookbook electronics (find a circuit and build it),mostly lighting with the 555 timer. Thanks.