low tech Signals

Model Railroader Electronics and DCC
1

i’m helping someone build their layout and the owner is less-tech savy. I think the following circuit is a possible solution, no processor and no digital electronics, voltage polarity controls two signal aspect. KISS

One of two LEDs wired opposite one another are powered with either +12 or -12V. A simple block detector (no delay circuitry) drives a relay which forces its output to -12V to indicate a Stop. Otherwise, the relay passes the +12/-12V controlling a turnout. If the turnout is aligned to the route, +12V goes to the relay indicating Clear or Approach (yellow). If the turnout is not aligned, -12V goes thru indicating Stop.

the 12V EA2-12NU relay coil has 1k+ Ohm resistance: ~12ma to energize the coil

If the switch machine is wired with the opposite voltage, the relay voltage and LEDs can be reversed (+12V indicates Stop), or maybe the switch machine wiring can be reversed.

the 2nd contacts on a DPDT relay can be used to control the signal in the opposite direction

if more than one turnout is involved, DPDT toggle switches can be used to route a control voltage or force an indication similar to the relay.

2

I think that would work OK except I don’t understand your term “Yellow”, from a Bi-Color LED wouldn’t that would require AC to drive both the red and green simultaneously.

Mel

My Model Railroad
http://melvineperry.blogspot.com/

Bakersfield, California

I’m beginning to realize that aging is not for wimps.

3

assume 2 separate LEDs. if mainline, red/green, if the diverging route, red/yellow. but I guess it should really be green over/under(?) yellow.

4

Actually, the signals in the opposite direction should be controlled by the block detector for the signal block on the other side of the turn out.

Are contacts 1,2,3 a manual toggle, or contacts on your latching relay circuit for multiple panel locations?

I see the simplicity here, as you know I use basically the same circuit. But to get consistant prototype action, you need the logic stream to be detection first, route second. This will require a few more contacts.

And again, are you just looking for “traffic lights” at turnouts or do you plan to use prototypical multi head signals approaching the point end of the turnout?

It may take a day or two, but I will do a drawing showing how this circuit would apply to all routes in both directions.

Sheldon

5

Approaching the points, there would normally be two heads, upper head, green, yellow, red. For this circuit the yellow would be a dummy.

Lower head would often be just two aspects, red and yellow.

From the frog side, the main route would have one head all three aspects, again in this circuit the yellow would be a dummy.

The siding would likely be just two aspects, red and yellow.

So four signal heads total.

Sheldon

6

So, to be reasonably prototypical, approaching from the points, set to the main route, that signal would be green over red with no train ahead.

With a train ahead, it would be red over red - full stop.

Set to the diverging route, with no train ahead, it would be red over yellow, telling us clear at restricted speed on to the diverging route. Detection of a train ahead would agin give us red over red.

From the other direction, each track would show red or green/yellow depending on route and detection ahead.

Sheldon