Another Walthers Grade Crossing Question

Model Railroader General Discussion (Model Railroader)
1

I have a grade crossing right after a switch. Could I put anther set of photo cells in the branch from the switch? Would it still work or would the additional cells interfere with those on the main line?

Thanks for any advise.

2

Why not go with block detection, then you can forgo the photo-eletric cells?

David B

3

I must must humbly differ in opinion.

Photo electric cells are fine. Personally, I find them a lot more versatile than block detection unless the blocks are really short.

I know when a train is safely in hidden staging. (as it enters: LED 1 on, then LED 2 on, then LED 1 off, LED 3 off)

Block detectors won’t tell you this.

You can use additional photoelectric detectors sets with most systems. The question is whether you need to place them in series or parallel with the first set. Check the documentation for your controller.

Karl

4

there is nothing in the documentation that refers to series or parallel.

I’d like your thoughts

5

If the Walthers controller is anything like our Grade Crossing Pro controller then I’d say series. Here’s why:

  1. A photocell is a light sensitive resistor.

  2. When you connect resistors/photocells in series you get the simple SUM of their individual resistance.

  3. A covered photocell has a higher resistance than an uncovered photocell.

  4. Covering one or both photocells in a series pair results in a higher total resistance than the two individual resistors uncovered. As such you end up with an “OR” type of operation.

Make sense?

Chuck Stancil

Logic Rail Technologies

6

What do you mean by “OR” operation?

Thanks

7

By “OR” I mean that when one photocell OR the other(s) is covered, the controller will consider this as “detected”. So, if you had a turnout and put one photocell in each leg of the turnout (i.e. past the frog) and those two photocells were wired in series, whenever a train on either leg of the turnout covered the associated photocell the controller would detect it.

Chuck Stancil

Logic Rail Technologies

8

OK thanks I’ll try it

9

[2c]

Thats how I have my signal system hook up. When a train enteres a block it covers one of the cells on that particular end causing the oposite end to turn red. It works great and quite simple. Logic Rail systems are IMO the best!

10

Chuck, I think I spoke to you several times while hooking up my system. Works great, thanks. [bow]

11

There is a crossing blinker system on my layout by Marsden Electronics that uses photocell detectors. I have a switch just past the crossing and mounted the photocell at the frog of the switch. One photocell covers both routes that way. Unless you need more distance from your crossing you might try the frog location for the photocell.