Will a latching relay work?

[tramcar trev]

I recall some signs at tram termini that were at the end of a section of single track that was around a corner from the junction of the double track that were near the double track junction that lit up when there was a tram at the terminus... I'm thinking that a latching relay tripped by a reed switch would turn the sign on, when the tram passes back over the reed switch another pulse would turn it off, turning of the sign..... I'd be using the same magnets on the trams as used to activate the other signals. Thoughts? Ideas?

 

[nicebutdim]

Yes it will work, but you'll require 2 reed switches and a latching relay similar to this http://www.ebay.co.uk/itm/12v-dual-...al_Components_Supplies_ET&hash=item2eb8fb9517 < Link To http://www.ebay.co.uk/itm...mp;hash=item2eb8fb9517 internal wiring diagram printed on top of relay.
Place the reed switches a couple of inches apart so that as the tram goes into the section it passes the first reed that turns the sign off (which would already be off) and then passes the reed that'll turn it on. When coming out of the section the on reed will be triggered first (which won't make any difference as it'll already be on) and then pass the off reed, switching off the sign.
The latching relays have 2 coils, which would be wired to the reeds respectively.

 

[steve parberry]

Yes it will work, but you'll require 2 reed switches and a latching relay similar to this http://www.ebay.co.uk/itm/12v-dual-...al_Components_Supplies_ET&hash=item2eb8fb9517 < Link To http://www.ebay.co.uk/itm...mp;hash=item2eb8fb9517 internal wiring diagram printed on top of relay.
Place the reed switches a couple of inches apart so that as the tram goes into the section it passes the first reed that turns the sign off (which would already be off) and then passes the reed that'll turn it on. When coming out of the section the on reed will be triggered first (which won't make any difference as it'll already be on) and then pass the off reed, switching off the sign.
The latching relays have 2 coils, which would be wired to the reeds respectively.

Thats IT!!!!!
I Have been having trouble in working out how to switch some contacts over and can only find two coil relays.....but now it easy thanks to your two reeds mesage

Bl**dy simple when you think of it

 

[nicebutdim]

Cool, I like it when I actually help someone
I have single line bi-directional running, using this method for my signalling. 100% reliable. If you have signals further up the line, or blocks, you can run extra leads to the reeds for the next signal so that when the train sets the signal to red, the signal in the previous section will go back to green, and vice versa. (diodes have to be used here though or the signals change undesirably)

 

[steve parberry]

Cool, I like it when I actually help someone

I Want to use it to change the polarity on my turntable bridge deck, but it has to remember what way round it is when its powered down at night... there by using the latching relay no problem but how to switch it as the bridge end passed a suitable switch..now if i install four reeds two for operation 180 degrees apart as the end of the bridge deck complete with magnet passes then hey presto the relay will change over.

 

[stockers]

If I understand relays correctly (and I might not!), is there a need for two reed switches. Could not the contacts on the relay switch the wiring to the reed to unlatch the relay on the return of the magnet?

 

[steve parberry]

Most Latching relays have two coils that pull a mechanical switch thus in fact two seperate devices.
coil 1 will pull the switches closed
coil 2 will pull the switches open

Thus if power is removed the relay will remain in the state it was last left in with no power applied.

There by you need to have the reed or whatever switch device to operate each coil as a seperate item.

For my application the turntable can rotate either direction and therefore will need four switchs(reeds) to operate two to energise the pull coil and two to energise the release coil. These will need to be on either side if the turntable.

The rail +L and -R will need to swap as the turntale rotates,to -L and +R
(where += Plus, - =negative, L= rail one and R= rail two)

I did try a reverse loop unit but this will not work as the switch rail combination is reversed as the turntable rotates.


Simples

 

[nicebutdim]

If I understand relays correctly (and I might not!), is there a need for two reed switches. Could not the contacts on the relay switch the wiring to the reed to unlatch the relay on the return of the magnet?

Theoretically that could work, but is not foolproof. with the one reed system; Say if a tram comes past the sign and turns it 'on', then you remove that tram from the track and place another tram so that it passes the sign in the same direction as the previous one, it'll then turn the sign 'off' when the sign was wanted to still be 'on'. With the two reed system the tram will always have to pass the 'on' reed after the 'off' reed (or vice versa if running the other way).

 

[steve parberry]

If I understand relays correctly (and I might not!), is there a need for two reed switches. Could not the contacts on the relay switch the wiring to the reed to unlatch the relay on the return of the magnet?

Theoretically that could work, but is not foolproof. with the one reed system; Say if a tram comes past the sign and turns it 'on', then you remove that tram from the track and place another tram so that it passes the sign in the same direction as the previous one, it'll then turn the sign 'off' when the sign was wanted to still be 'on'. With the two reed system the tram will always have to pass the 'on' reed after the 'off' reed (or vice versa if running the other way).

AH but, if two trams enter the same section then when the first tram leaves it will deactivate the sign even though a tram remains...

Now we are into the realms of counters as well:wits::wits::wits:

If your are digital then feedback modules are the way to go but expensive:thumbdown:

 

[nicebutdim]

If I understand relays correctly (and I might not!), is there a need for two reed switches. Could not the contacts on the relay switch the wiring to the reed to unlatch the relay on the return of the magnet?

Theoretically that could work, but is not foolproof. with the one reed system; Say if a tram comes past the sign and turns it 'on', then you remove that tram from the track and place another tram so that it passes the sign in the same direction as the previous one, it'll then turn the sign 'off' when the sign was wanted to still be 'on'. With the two reed system the tram will always have to pass the 'on' reed after the 'off' reed (or vice versa if running the other way).

AH but, if two trams enter the same section then when the first tram leaves it will deactivate the sign even though a tram remains...

Now we are into the realms of counters as well:wits::wits::wits:

If your are digital then feedback modules are the way to go but expensive:thumbdown:

S*d that