Latching Reed Switch

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bulleidboy
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Latching Reed Switch

#1

Post by bulleidboy » Fri Nov 15, 2019 4:42 pm

Iv'e looked at a "coach lighting kit" from Layouts4u - it consists of a strip of 3v LED's, latching reed switch, and a CR2032 battery + holder - all at £6.
You stick the LED's and the reed switch to the coach roof (inside), the battery holder sits at the end of the carriage. You wave a magnet over the coach roof and the lights come on - again and they go off. With a magnet fixed just inside the tunnel when exiting the fiddle yard, the lights would come on, and they would be turned off when the train re-entered the fiddle yard. £6 a coach is not excessive, but looking on ebay, battery holders and latching reed switches are as cheap as chips, so you could probably do several coaches for £6.
Question: some of the reed switches are described as "open" - what does this mean?

I have attached the short video showing how these lights work - https://www.youtube.com/watch?v=iLimSOw4zI4&t=26s
Last edited by bulleidboy on Fri Nov 15, 2019 4:44 pm, edited 1 time in total.
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RogerB
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Re: Latching Reed Switch

#2

Post by RogerB » Fri Nov 15, 2019 4:43 pm

Pretty sure the eBay ones will not be latching.

AFAIK "open" means the contacts are open until magnetised when they close - but they re-open as soon as the magnetic effect is lost.

I have this system on my Railcar - very effective, when I can find the darned magnet!

R-
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Re: Latching Reed Switch

#3

Post by teedoubleudee » Fri Nov 15, 2019 6:21 pm

Most people are shocked when they find out how bad I am as an electrician

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Re: Latching Reed Switch

#4

Post by teedoubleudee » Fri Nov 15, 2019 6:52 pm

RogerB wrote:
Fri Nov 15, 2019 4:43 pm
Pretty sure the eBay ones will not be latching.

AFAIK "open" means the contacts are open until magnetised when they close - but they re-open as soon as the magnetic effect is lost.

I have this system on my Railcar - very effective, when I can find the darned magnet!

R-
Correct Roger, though usual practice is to call them "Normally Open" or NO, same as contacts inside a relay. NC or "Normally Closed" have closed contacts ie a short across them until a magnet is brought close and they open.
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bulleidboy
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Re: Latching Reed Switch

#5

Post by bulleidboy » Fri Nov 15, 2019 9:43 pm

Thanks Roger and TWD for the explanation. I thought it might be cheaper to make your own - as I said £6 a coach is not bad, but the prices for some of the items required is very cheap. I'll get probably buy three kits, which will enable a rake to be lit, and then see how we go. BB
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Re: Latching Reed Switch

#6

Post by RAF96 » Sat Nov 16, 2019 11:30 am

As the link says the reed switch latches when the magnet is passed over it then de-latches when the magnet is presented again. Similar to a push-push switch. The blurb infers the magnet does not have to be present all the time the latch is closed.

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Re: Latching Reed Switch

#7

Post by teedoubleudee » Mon Nov 18, 2019 2:12 pm

After posting the link (#3) on where to purchase these switches I decided to buy a couple myself to play with. I haven't done so yet, but some might find the instructions printed on the envelope that the device is supplied with interesting, particularly regarding the use of alternate magnetic poles to switch the device on and off. See photo. Very quick service from Layouts4U by the way.

Image
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