What’s a relay? (Sort of....)

[D9012]

I’ve designed a layout that will use Seep PM1 point motors, just over 50 of them.   
the scheme currently plans SPDT switches on the panel, with frog polarity handled by the switch in the motor.  
I had hoped to have LEDs lit on the panel to show track selected - but as the Seep needs passing contact switches, I can’t link a LED circuit to the point switch ( if I had used DPDT instead).  
so, I thought about using EITHER a micro switch at each point - along with 300m or more wire to the panel - OR a latching relay linked to the SPDT switch on the panel.  
 

here I get completely and utterly bamboozled.     What do I need?  And I want it to be cheap and simple!!!   CPC Farnell lists hundreds of types, but what’s what -  mechanical/magnetic/power/signal etc and then how do I wire it all up?    I’ve read a number of threads and the technical descriptions and to my very simple mind it’s all nonsense!!!!   What I need is a straightforward- 1) buy this. 2). Connect this to that).  Switch it on and play.  Ahem!!!!

 

and to start off, is this one any good?

https://cpc.farnell.com/axicom-te-connectivity/v23079b1201b301/relay-tht-dpdt-latching-5v-dc/dp/SW04927?ost=Sw04927#anchorTechnicalDOCS

 

thanks in advance 

 

[ejstubbs]

Guagemaster do the GM500 relay for precisely this kind of function. It may not be as cheap as buying 'bare' components (but then Farnell are far from cheap anyway IME) but they are purpose-designed for the job in question. (They are also available in slightly more economical three-packs).

 

This wiring diagram for the GM500 shows the second set of contacts on the relay being used to illuminate a two aspect colour light signal, which could equally well be indicator LEDs on a control panel.  (Note that the diagram also shows the first set of contacts on the relay behind used for frog polarity switching. Given the well-known poor reliability of the SPDT switch built in to the SEEP PM1, this is probably a good idea.)

Edited January 20, 2022 by ejstubbs

[D9012]

Thanks;   The wiring diagram is helping to make it more sense already. However!   I don’t want to lay out the best part of £300 for this type of product, I may as well fit 50 micro switches and 300m of wire at around perhaps £200 (especially as I already have a lot of wire)

 

the products on Farnell website are

much cheaper, so if they are not the cheapest, what other companies are worth investigating??   The example I included in my post is only £1.70 if buying 50 or more - but only if it’s suitable of course!
 

[73c]

Would these be of any use?

 

https://www.ebay.co.uk/itm/282576987893?hash=item41cae6a6f5:g:CYgAAOSwC6NhCwQI

[D9012]

73c that is very interesting

 

so, presumably, I want a 12v version as that deals with the point motor voltage, but is that right with a 16v CDU????

is it a latching type relay?

 

and I see the 8 relay version has 8 input tags, a ground and a VCC.      I can see 8 inputs coming from one side of a DPDT switch, but what’s the ground and VCC?!!!!

 

cheers

 

 

 

[73c]

Reading your first post again, how about this?

https://www.heathcote-electronics.co.uk/point-indicator.html#:~:text=POINT INDICATORS&text=The purpose of the POINT,removed from the model railway).

or

https://www.ebay.co.uk/itm/164080297562?chn=ps&var=463699688637&norover=1&mkevt=1&mkrid=710-134428-41853-0&mkcid=2&itemid=463699688637_164080297562&targetid=1278447513267&device=c&mktype=&googleloc=9044978&poi=&campaignid=14727339348&mkgroupid=127909237815&rlsatarget=pla-1278447513267&abcId=9300672&merchantid=115025230&gclid=CjwKCAiA0KmPBhBqEiwAJqKK48SHH4Gk5rNrZu0NJ5E9-1hn6UcCAZa0W1BZ13-owBUW3B4iKJFSdBoCM8AQAvD_BwE

[Brian]

Hi

In your opening post you say "I can’t link a LED circuit to the point switch ( if I had used DPDT instead)."  You should not be using locking switches of any pole type with solinoid motors unless some other precautions are taken.  The normal switch to use is a sprung to centre Off type, often referenced as (On)-Off-(On) where the bracketed (On) cannot remain in that position when the lever is released - It springs back to the central Off position via its own internal spring mechanism.    So these switches cannot illuminate any LEDs as their contacts open when they spring back to centre.   

The logic boards often called 'Point Position Indicators'  are a good idea, but they only show that the switch has moved from one position to another.  It is therefore possible to have a failure to throw on the point itself yet still indicate incorrectly that the point has moved!   The Twin coil latching relay also only proves the pulse has been sent, not that anything has operated correctly.    By using a switch (micro switch is usually used) that's operated by the point motor moving is by far the best option and is as near as practicable to proving the point has moved over.    A small lever type micro switch mounted next to the point motor and has its lever worked by the movement of the solenoids drive pin is IMO a good as near as true point position indicator switch one can obtain other than a directly fitted motor operated switch such as the Peco PL13 (which isn't the best of switches!) or better their PL-15.   

If at any time a surface mounted solinoid motor is used a micro switch can be fitted on the oposite side to the motor and its lever worked by the points moving stretcher bar.     Small micro switches can be obtained for a few pennies each. Examples are here  Micro switch examples but there are many suppliers.

[D9012]

Thanks both, all help appreciated 

73c - I think that’s moving to more cost/complexity than I hoped.  

Brian - possibly you misunderstood or I explained poorly BUT!!!   I’m using passing contact switches for the solenoid motors, and wanted to investigate the ease of a latching relay to keep the LED on.  
from what you say I may well be veering back to using micro switches on the points and just putting up with some cable runs to the panel.   

[SamThomas]

14 hours ago, 73c said:

Would these be of any use?

 

https://www.ebay.co.uk/itm/282576987893?hash=item41cae6a6f5:g:CYgAAOSwC6NhCwQI

I bought some of these for similar use, but they don't stay "latched" during power off & on.

[SamThomas]

If you are mounting the switches together (i.e. NOT on a scematic) you could look at the PECO PL26R - they will give you a visual/mechanical indication.

 

Also, have a look at some of the Viessmann switches - not cheap though but less "spagetti" under the boards & probably a lot less work.

[Lurch]

 

On 21/01/2022 at 11:16, D9012 said:

I may well be veering back to using micro switches on the points and just putting up with some cable runs to the panel.   

 

I'd always do it that way anyway (wiring back to the panel) as then the LEDs follow the points if they are switched manually locally and you can see if the points don't fire over when you press the button on the panel.

 

On 21/01/2022 at 12:47, SamThomas said:

I bought some of these for similar use, but they don't stay "latched" during power off & on.

 

You don't need them to stay latched. Use the contact on the Seep to trigger the relay (or more specifically, 2 relays) and then use the contacts of one for the frog and the contacts of the second for the mimic.

 

Going further you can use multiple relays for e.g. interlocks to stop opposing points being set or to remove track power when a crossover is switched to go from one loop to another. Those units are pretty handy for loads of things, you could use 1 8 module unit and wire multiple points to it or keep it simple and use a 2 module unit per point.

 

Edited January 30, 2022 by Lurch

[SamThomas]

11 hours ago, Lurch said:

 You don't need them to stay latched.

Without going into loads of detail for my use they do need to stay latched during power off/on.

 

I was mearly pointing out that the relay banks shown do not stay latched during power off/on despite what the blurb says about them.

[Michael Hodgson]

The switch on the SEEP motors is notoriously unreliable.  I certainly wouldn't want to use it to feed the frog, or as part of some circuit that causes the point to throw.

 

Having said that however, it's less of an issue if those contacts are used for a function that is less critical to operation - indication back to the panel of the point's position.  Many model railway circuits that include an indication are misleading in that they only show what you last instructed the point to do, not whether it actually worked.  The SEEP's contacts move with the pin that moves the tie bar, so it's reasonable to assume that if it makes contact at all, it will agree with the the way the point actually lies.

 

On the prototype, signalling systems are designed to detect the actual position of the tie bar, and this is often fed back to the box to give a visual "N" (Normal) or "R" (Reverse)  indication for the point  - or neither if the point  has failed to move fully over, for example if the blades are jammed by a piece of ballast.  As this is a safety issue, the signals can't be cleared unless the lie of the points corresponds to the position of the signal lever or its equivalent and locked there.  An indicator needle would hang in a position marked "Wrong" or an NX panel might have a flashing light labelled "Out of correspondence".   Whilst all that is generally considered overkill on a model, it is still desirable that if any panel indication is given, it should at least be correct, which is why the SEEP contacts can be useful - however you might find the extra wiring somewhat tedious.   

[Michael Hodgson]

In case there is confusion over latching relays ...

 

A simple or non-latching relay is just a two-position switch which changes position when a coil is fed by a current.  When that current is interrupted, it falls back to its  original position.  It can have several "poles" or sets of make/break contacts.

 

A "stick" or holding circuit can be made by wiring one of the poles of such a relay so that one of its make contacts feeds back to its own coil, thereby keeping it in that position.  So you can cause it to operate with a push button, and it will stay there even when you release the button.  

In order to get it to drop back, the stick circuit also needs a break switch (for example a normally made push button or contact), or alternatively the coil could be shorted out.

 

A latching relay changes its position in response to a pulse from a momentary feed from an On switch or from an Off switch.  

The important difference in function between this and a stick circuit is that a latching relay holds its position even if power to the whole system is turned off, but a stick circuit loses its memory.

 

True latching relays tend to be more expensive that ordinary ones, which is why stick circuits are sometimes preferred.

Edited January 31, 2022 by Michael Hodgson

[Lurch]

6 hours ago, Michael Hodgson said:

The switch on the SEEP motors is notoriously unreliable.  I certainly wouldn't want to use it to feed the frog, or as part of some circuit that causes the point to throw.

 

Also a consideration, but I'm planning on using electrofrogs in conjunction with the Seeps, 2 unreliable methods must make it reliable right?!

 

The Seeps are OK for what they cost, same as the electrofrog points really. If money was no object I wouldn't use the Seeps. Lots of layouts use no point motors and have no auxiliary switching at all and work perfectly fine.

[DCB]

You can get suitable microswitches for DC polarity of LEDs for about 10p a throw and use telephone wire for LED wiring which puts the cost down towards £10 instead of £300.  I use  10p microswitches operated by the point tie bar outside for DC polarity. I say DC as usually DC is less than 1 amp and DCC basically is not.  Great sophistication is wonderful on a five point shunting plank but multiplied by 10 it gets expensive.

[Titan]

These are also a good solution:

 

https://www.mouser.co.uk/ProductDetail/Panasonic-Industrial-Devices/TQ2SA-L2-12V-X?qs=YINDDaGsG3G1Dq5YIx48ZA==&mgh=1&vip=1&gclid=Cj0KCQiA5aWOBhDMARIsAIXLlkfb9k1AGms0UQGIYs2MYRUnKw3OwEqqdh9_h1eI8sPt0jsaWY8EeVsaAhlfEALw_wcB

 

Latching relays that you can put behind the control panel, with the coils wired in parallel with the point motor coils. You can have as many as you like on one set of points for frog switching, signalling, panel indications, and place them anywhere you like - no need to be anywhere near the points or control panel if you wish to place them somewhere more convenient, or even just to reduce the length of the wiring required.