Twin coil machines need a momentary pulse to operate. The only way I have found to get an steady indication of the current position is to wire an Atlas Snap Relay in parallel with the switch machine. Perhaps someone else has a better solution. This shortcoming is one reason I won't be using twin coil machines on my current layout.

I think your idea on installing an Atlas Snap Relay is a good one. Keeps it simple. There is a brand of Twin Coil switch machines that comes with SPDT contacts. They're made by Tenshodo. Not sure how available they are.

Chris Palomarez

Thanks, All my turnouts have twin coil machines. I do have tomar dwarf signals wired to a few and they work great. I wanted to try something different was just unsure if BLMA would work. I like their style.

I do have Tenshodo machines. Do BLMA have a colored wire for each LED like tomar dwarfs do??

You could also use a generic latching relay http://www.digikey.com/product-detail/en/IM46GR/PB1091TR-ND/1633977 if the price is better.

Hi,

there are lots of circuits how to get indication for twin-coil switch machines, e.g. http://www.1zu160.net/elektrik/images/weichenmeldung.gif

These range from five to fifty parts per turnout...

The best one I remember used capacitors in series with the actual coils, thus providing a power spike for switching, protection for the coil (prevents steady current through the coil) and they had an option to add an LED, also. Still it was only a few parts (resistor, capacitor, diode). It really was the best circuit for twin coil switch machines I ever found.

Pity I cannot find it anymore.

If anyone has this circuit, please share...

Greetings.

i have used this one. 

http://home.cogeco.ca/~rpaisley4/ToggleTwin.html

Ken Stapleton, a Canadian, has a number of model train control circuits he has developed. He sells them either assembled or in kit form and variety of quantities. One of his designs, the model 751D and 751K may be the choice for your twin coil machines. You may want to see what he offers here:

http://www3.sympatico.ca/kstapleton3/751D.HTM

Hi,

as mentioned previously, there is a pretty nice circuit for twin-coil turnout machines. After a bit of a search last night, I found it:

http://home.cogeco.ca/~rpaisley4/ToggleTwin.html

Specifically the first circuit seems to be very appealing, few components and all the nice features:

- protection of coils / switch machines

- providing a current surge from a capacitor and thus

- protecting the power supply from that surge

- optional: indication

Have fun...