Relays

Basic electrical and electronics, such as DC/Analog control.
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pete12345
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Relays

Postby pete12345 » Mon Nov 08, 2021 6:38 pm

I'm starting to wire up my layout, and due to the strategy I've chosen, I'm interlocking the switching of power to various sections through the setting of key points. This enables, for example, a train to be brought into a platform road using the main line controller while the station pilot is under the control of another. Rather than use 4PDT switches everywhere, I want to localise the wiring by using relays close to each point/section.

What have other people used? Having built control systems as work, DIN rail stuff appeals due to the neatness and ease of wiring up, but it's not easy to find a suitable option which doesn't break the bank! I:m wondering whether multiple single-pole relays might work out cheaper in the end, or whether there's a suitable multi-pole item which I haven't yet found.
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Bufferstop
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Re: Relays

Postby Bufferstop » Mon Nov 08, 2021 10:01 pm

I've used a miniature 12 volt 4 pole change over relay, I think it came from Railroom Electronics, as there's only one I eschewed the plug in base it's held in place by a square of velcro hooks and loops with self adhesive backing. I wanted an ammeter on the panel for use with a hand held controller. There was a spare core in the controller lead. I fitted sub min microswitch operated by reversing switch to pull in the relay and reverse the connections to the ammeter when going in reverse.
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Suzie
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Re: Relays

Postby Suzie » Mon Nov 08, 2021 10:59 pm

The BT47 style of relay with DIP pinout usually works out to be the most reasonably priced for a reliable product, but you will have to mount the relays on stripboard. They don't look as impressive as the DIN rail option, but they are small enough to fit under the layout and won't need you to build a relay room.

4-pole relays are not always easy to get or very cost effective, so you might like to just get a pair of 2-pole relays instead.

These very small 2A relays from Rapid might be a good place to start:-

https://www.rapidonline.com/hongfa-hfd3 ... 2a-71-4731

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luckymucklebackit
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Re: Relays

Postby luckymucklebackit » Tue Nov 09, 2021 2:35 pm

I have used a few in the past, started off using old GPO syle relays that I got as a job lot donkeys years ago, started using ones that I sourced off Ebay and they work equally well, only issue I found wit h them was that the prongs looked to be were designed to be plugged into a PCB and needed more care soldering wires to. WOrked out well in the end.

See some of my work here https://www.newrailwaymodellers.co.uk/Forums/viewtopic.php?f=22&t=33932&start=120

Jim
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Bufferstop
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Re: Relays

Postby Bufferstop » Tue Nov 09, 2021 5:52 pm

The first computer I got to see the inside of was all relays. You didn't load a program, you wired it on a patch panel. Each step was instantaneous, but you needed to shift wires around to move from step to step. Press go and it would rattle through a sequence of "if thens" at lightning speed and stop you then deciphered the meaning of the lamps it had left on, you either then had an answer or a request to change something. It would be quite capable of running a layout, trains operating sensors would tell it to move on, depending on what was where it could do the next step. The layout built at Alton Towers in the late 50s nearly did it the same way.
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Teedoubleudee
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Re: Relays

Postby Teedoubleudee » Tue Nov 09, 2021 8:11 pm

I have added a lot of automation to my layouts and relays are great for this. I currently use those logic driven ones that come pre installed on a pcb with along with the necessary components. The come in singles, 2, 4, 8 or 16 relays on board and for reasonable prices. Unfortunately they only use one set of changeover contacts. I've also made a layout that used multiple contact sets to run multiple trains using relays saved from days as an engineer for electro mechanical computers from the 1960s.

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luckymucklebackit
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Re: Relays

Postby luckymucklebackit » Wed Nov 10, 2021 4:09 pm

One lesson I learned from my last layout was when designing the logic circuit to always wire relay coils in parallel, never in series. My first attempt had some in series and they would not activate due to me completely forgetting my basic electronics.

Jim
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Flashbang
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Re: Relays

Postby Flashbang » Wed Nov 10, 2021 7:13 pm

With years of experience of using relays for safety critical interlocking on BR, a relay is very simple device for switching multiple circuit's.
BR in their later years used 930 style relays with around 8/8 or 12/4 contacts The first number is the contacts that make when energised and the second is the ones that break connections when energised. These in BR terms are called front and back contacts. Front makes when energised backs are made when the relay is de energised.

On my model railway I have used MERG relay PCBs and BT47 relays (DPDT) but their PCB allows for both single coil relays and dual coil latching BT47 relays. My relays I order in from China via Banggood.com
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Bufferstop
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Re: Relays

Postby Bufferstop » Wed Nov 10, 2021 9:46 pm

I recently acquired a 12v motor speed controller with Bluetooth remote, which does slow starts and stops and has useful things like adjustable start voltage, rather cheap as it was the last one left. What does it use to do on/ off and forward/reverse, a couple of 5volt relays, works quite well plugged in in place of one of the hand helds.
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fourtytwo
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Re: Relays

Postby fourtytwo » Wed Nov 17, 2021 8:08 pm

Bit late I know but for many years I used 4PDT cradle relays also known as euro relays made by many manufacturers.
These have quite chunky solder tags and sockets are also available and mounting plates for mounting blocks of 6.
As my layout has downsized dramatically I am currently selling some on *bay just to see if there is any interest, you might like to search for "model railway relays X6" meaning batch of 6 in the auction.

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