Originally Posted by necrails:
Dale, thanks for chiming in, I was hoping you would. I have been on that link and remain stumped (dense?) What I am stuck on is this, where does the outside insulated rail connect to the relay? At the coil connection or to the rectifier? Looking at the very last diagram in your link the GREEN wire from the trolley transformer is labeled TRACK OUTER RAIL. Is that the outer rail for the track or insulated rail?
Here is the diagram in question. Click to enlarge. All we are concerned with here is the coil circuit. The contacts I think reversed polarity on something like a trolley.
Note the relay transformer goes to a bridge rectifier. Not shown across the + and - you could put a capacitor. That will give filtered DC and boost voltage 41 percent,so 18 VAC becomes about 24VDC. That is a good voltage for the timers I use.
The + of the bridge goes to one lead of each of the 3 relay coils. It could be 3 or 300,whatever you need as long as you have enough transformer wattage. I use 24VDC coils so I have a 24 volt system. It powers every relay and timer on my layout.
The - of the bridge as shown goes to the ground or common of the track transformer. The common also goes to the outer rail of every loop of the layout.
An insulated outside rail can be made for each relay with 2 plastic pins. That insulated section wire goes to the other lead each relay coil. The insulated section should be long enough for at least a couple of cars to sit on. The metal train wheels connect the outside insulated rail to the ground rail that is already connected to the U. That completes the circuit and powers the relay coil. The relay stays on until the wheels leave the section and its respective capacitor discharges. Small value capacitors keep the relay from chattering when a train just enters the block. Large value capacitors can be used to create a delay off situation. Relay contacts do the switching required. Note this circuit is independent of the track center rail circuit and will even work when the train is not powered.
Note with this arrangement insulated rails can be combined,that is wired together and still kept separated electrically speaking with diodes. Suppose you had a triple crossing and wanted to activate a crossing gate or flasher. This can be done using only 1 relay,with a diode in series to each insulated rail. If on one of the 3 loops you wanted to also activate a block signal,specific for only that loop you can just add a relay for that insulated rail and switch the desired accessory and not effect the triple crossing. Current does not flow through opposing diodes. Say you want a trolley to stop in 4 places on a loop,the insulated outside rails can be wired together using a single relay.
You can also do direction logic. Here is a bi directional crossing gate for example. It also shows the relays powered with the DC- as the common.
LINK
Relays are so much cheaper and more flexible to use that IR detectors. Once you wire a few and see how it works, the get a lot easier to wire.
If when laying track you divide the outside rail up into small sections and run all the insulated outside rail wires to a barrier strip,you can now or later activate any track side accessory,easily by just adding the relay. Unused outside rails can be connected to common. Suppose you divide a loop into 12 sections for example like on the hour markings of a clock. If you want a flasher to operate on both sections 6 and 7,you can do it easily by using that wire and hooking it to a relay. If you want a train to stop on block 4,you can do that. You can make is it stop every time or every other time or make a random circuit where you can set the probability of it stopping. If only one train is run on a loop,you do not need an insulated center rail to do this. If section 2 is uphill,you can boost the voltage (conventional). If section 9 and 10 are downhill,you can reduce the voltage.
A starter set type transformer can power a lot of relays on an average layout. My layout is large so I use a 180W brick. Even 200 relays all activated at once is not a problem. My relays provide a complete train throttle.
To answer your question about the diagram,the green wire goes to common,the track outer rail that is not insulated. The other leads of the relay coil are connected to an outside insulated section. #22 wire is fine. COLOR code your wire or you will go insane.
Dale H
