# Reed Switch question



## OilValleyRy (Oct 3, 2021)

When it comes to electronics, I’m like a monkey banging two rocks together.

Reed Switches; they’re magnetic and that’s the extent of what I know of them.

Question: As a non-hypothetical example, if you wanted to illuminate a caboose using DCC track power and a reed switch to turn the light on & off, will a reed switch alone turn them on and keep them on until you turn them off again (akin to a solenoid switch machine)? Or is the Reed Switch just momentary and some other component being needed to keep the lights on or off until the switch is actuated again? If so, what sort of component would that be?

Incidental Question B: Would two reed switches in a single caboose, one at each end mounted under the interior roof be far enough apart to not have interference with one another? Is there a minimum distance for that magnetic field?

I’m trying to simplify my caboose plans and eliminate both the cost and operating hassle of using decoders in lieu of a simplistic magnetic wand… That even a monkey banging two rock together can explain to others/operators?


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## MichaelE (Mar 7, 2018)

You will need a magnet to activate a magnetic reed switch.

Contacts can be kept closed depending upon the amount of current draw through the circuit and the switch's rating.

The leaves in a reed switch are made of an alloy that does not retain magnetism but will react in a magnetic field.

Magnetic reed switches are often used to close or open a relay that controls a higher power circuit such as I use for semaphore operation which uses a solenoid to operate.


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## OilValleyRy (Oct 3, 2021)

A magnetic wand is no problem. I just wasn’t sure if a reed switch defaults back to a “center off” position when the magnet is removed? The draw would be a single grain of rice bulb or similar physical size LED.









Not a great view but those aluminum housings on the ends contain red bulbs, one on each end, that I want to control independently.


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## traction fan (Oct 5, 2014)

OilValleyRy said:


> A magnetic wand is no problem. I just wasn’t sure if a reed switch defaults back to a “center off” position when the magnet is removed? The draw would be a single grain of rice bulb or similar physical size LED.
> 
> View attachment 579895
> 
> Not a great view but those aluminum housings on the ends contain red bulbs, one on each end, that I want to control independently.


OilValleyRy;

While there are exceptions, nearly all magnetic reed switches have only two contacts and they are "normally open" (meaning OFF the switch will not pass current) When a magnet is placed beside a reed switch the magnetism pulls the two contact reeds together. This closes the electrical switch and current can pass through to your light. The magnet needs to stay next to the reed switch to keep it "ON".
You might consider mounting the switch (s) low down on the car. A small magnet hanging down there would resemble a piece of the under the floor equipment common on cabooses. However, the reed switch will work anywhere you choose to mount it, as long as the magnet is right next to it. Depending on the strength of the magnet, you might be able to have about 1/16" to 1/8" between the magnet & reed switch. A second switch, at the other end of the car would not be affected by the magnet at the other end. If your magnetic reed switch is the common type, sealed in a glass tube, It will work best if the magnet is placed along the wide flat surface of the reeds. Placing the magnet along the narrow edges of the reeds reduces its effect.

Traction Fan 🙂


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## MichaelE (Mar 7, 2018)

Be very careful with the wire leads and don't bend them right at the tube. The glass is very delicate and is easily cracked by rough handling or bending the wire too close to the tube.


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## OilValleyRy (Oct 3, 2021)

Thanks guys.

I was not aware they are glass tubes. 
The clarification of the static open position helps, as does the suggestion of undercarriage equipment. But I think I’ll turn the idea on its head and do some sort of air conditioner or vent as magnet camo. That actually makes it easier still. AC unit always sits on the trailing end. 
👍


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## DonR (Oct 18, 2012)

To turn a caboose light on and off you should
use a simple 'on/off' toggle. It could be
mounted somewhere UNDER the caboose
frame. There are miniature
toggles available from the electronic parts stores.

Don


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## OilValleyRy (Oct 3, 2021)

DonR said:


> To turn a caboose light on and off you should
> use a simple 'on/off' toggle. It could be
> mounted somewhere UNDER the caboose
> frame. There are miniature
> ...


I don’t want to be lifting them off the track. I’ve seen toggles mounted in windows, but it is tricky to actuate them. That’s why I was going to use DCC decoders (12 years ago) but never did and these days I’d rather find a less costly and simplistic as possible method operationally.


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## kilowatt62 (Aug 18, 2019)

No need to lift car of track. Index finger on top of cupola to keep car steady, grab your H.O.G. Stick with other hand and reach under caboose and flick the switch. I think that might be easier than fiddling w/a magnet.


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## SF Gal (11 mo ago)

Another Item you may consider is a touch key TTP223 switch module!
















They sell them on E-bay and once you mount this to the top of the inside of your caboose roof, all you have to do is touch the roof of your caboose! This little beauty works through plastic! You place the "TOUCH" side up against the inside roof. You can configure the switch for momentary or on-off by soldiering A terminals or B terminals together. I comes with instructions and you should buy a whole lot of them because they are handy to have.
The picture above with clothes pin is part of my emergency car jack switch. I had a timed circuit made that times out after the hidden TTP 223 button under the plastic dash activated a count down timer to shut down the fuel pump. 
They can car jack my car but if I touch that location on the dash, in a minute, the car dies. You have to know where the touch area is on the dash to touch it again and restart the car. 
I was going to use this on the facia of my layout to have visitors be able to turn on and off individual lights and signs on the layout under a plexglass Startrek like panel.
You will have to reduce the incoming voltage to lower than 5.5 volts with a resistor or a Step Down Converter.
Just another suggestion but maybe at the edge of your electrical dexterity?


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