I would like to have at least one crossing on my layout with working lights. This item says specifically not for DCC layouts. I don’t understand why. It draws power from the track but why couldn’t that source be an aux power supply and not the DCC source? What am I missing here?
Thanks,
oldline1
This is the hook-up diagram from Walthers. It sure looks to me like you could get the power from another power source and it would work.
Well, according to Walthers, using it on a DCC layout can damage the controller.
So, why tempt fate?
Rich
That’s what I was thinking. None of the sensors or signals have any connection to the track or DCC power. The power feeds for the controller could be from my accessory power bus the way I see it.
You could always try it. 
Rich
I intend to but was just curious if anyone else had some input on DC vs DCC for it.
I don’t use the Walthers controller but I seem to recall that the track power is what told the sensors what the direction of travel was by detecting the rail polarity, something DCC will not provide.
Regards, Ed
If you’re running DCC, you may not want their controller. Both Azatrax and East Coast Circuits make them to run bi-directional and on DCC.
Also ‘Grade Crossing Pro’ from Logic Rail:
This is the one I use.
Regards, Ed
Walthers 949-4359 sounds like an excellent addition for a DC layout.
Since each crossing approach has a pair of sensors (presumably to ascertain direction of travel), I don’t see why rail polarity would matter. That connection to the rails is a mystery.
I agree. That’s what’s puzzling me. I don’t see the necessity for track connections. It seems, to me, the connections to their POWER PACK should be all that’s required. The sensors are independent of the track and the controller gets power from the POWER PACK so why would it not work with DCC? No track polarity involved.
Not sure if this will help:
Good Luck, Ed
Seems complicated.
I know this is not an answer for the original poster, but this is what I did.
I bought a $3 nano board, four 30 cent light sensors, and after watching a Youtube video, wrote a simple Arduino program that activates and blinks the lights for a double mainline.
I’m in my 70s and fairly dumb, so if I can do it, anyone can.
The only thing I’m going to change is substitute infrared sensors for the light sensors. It was a pain adjusting the program so the light sensors would work in certain room lights.
As I see it the main problem is that DC has a different polarity depending on the direction of approach. DCC has a fixed polarity. This must have some effect on the way the controller treats the approach and departure sensor signals.
I thought these systems worked by gauging both direction and speed by measuring the extinction times of the pairs of photodetectors. The polarity or even the presence of voltage on the rails at all should have nothing to do with operation.
I think the ‘argument’ is whether DCC track power with Lenz modulation (imposed square wave with reversing base DC polarity) is suitable to run a device built for rectified/smoothed DC input.
I find it amusing that this thread continues despite the fact that Walthers, the manufacturer, cautions that use if the controller on a DCC powered layout can damage the device.
Rich
Well, I don’t know if “argument” is the right word for my question or not.
The power source is an external power pack.
The photo sensors are powered by that.
The sensors work based on position inside the rails and don’t have anything to do with polarity.
SO…
WHY DOES IT HAVE THE 2 WIRES GOING TO THE RAILS THEN?
Just a confusing bit of wiring to me. What is their purpose?
The 2 wires would not go to the rails on a DCC layout; if you look at the diagram it indicates you’re taking ‘DC track power’ from a DC power pack or equivalent; taking it from ‘the rails’ is probably to shorten the wiring distance to wherever the controller is installed on the layout, close to the crossing. On a DC layout.
I note that the installation in the video is for a ‘DCC/DC’ layout. This obviously won’t have connections to the rails themselves even if part of the time the layout is operating in DC. And indeed he’s got some kind of connection to “an old Tyco power pack” that goes through some weird ‘loopback’ connection he doesn’t explain and then to a 19VAC connection … someone needs to explain what that’s doing, as I can’t.
I was wrong about how the sensors work. They work in pairs: the further away turns the flashers on (and disables the nearer sensor on that side), then the sensor immediately across the crossing turns the activation off.
I guess I’m blind as I see no explanation for those wires.
