Block Occupancy Detection

Discussion in 'FAQs' started by jdh, Jan 6, 2003.

  1. jdh

    jdh Member

    wanting to take a poll on how you are doing block occupancy.

    TWIN-T and derivatives

    Infrared optical

    optical [non infrared]

    reed switch

    i am thinking of applying an automated block control on the N scale layout [10x10 around the room shelf layout] and am wondering how happy people are with this.

    this is a 2 cab controlled layout [ok, 3, but i am not counting the yard] ;)

    traffic is generally one direction, but that is from habit mostly.

    a simple way to visualize this layout is to draw three circles.
    outside circle touches the middle circle at one place only [double slip]
    middle circle touches the inner circle in one place only [facing turnouts]

    inner circle does not touch outside circle.

    in practice, the inner and middle circles come together to go across a drop bridge to allow you to get into the room.

    the outer circle is a helix and loop for the hidden yard section.

    yes, i have read many kalmbach books on this, and have been a subscriber to MRR since about 1979.

    these books generally don't mention any pitfalls people experience in actual application.

    thanks to everyone for the support!
  2. sumpter250

    sumpter250 multiscale modelbuilder

    On the club layout we used TwinT. When we converted to DCC, all the detection was removed, and hasn't been replaced yet.

    TwinT(etc) detects current draw in the block. Doesn't detect rolling stock, or locos when there is no power applied. Constant intensity lighting, and track powered FRED, or caboose lights, can improve "train" detection.

    Optical. You really need two, closely spaced sensors, to insure "train" detection. With only one, you might be detecting the space between cars.

    Reed switch. Will only sense "the magnet" I'd use them for triggering something, but not for automated signalling.
  3. kf4jqd

    kf4jqd Active Member


    Hi jdh:

    A friend and I are building and going to sell some infrared detectors. They seem to work well. We are hiding them at signal lights, bushes, trees, and also in buildings.

    Another way is to use current sensors. As the locomotive passes over an area of track. It draws more current compared to the rest of the layout.

    You can also you photo cells also known as CdS cells. You can buy them at any local Radio Shack. I have an IHC railroad crossing that uses them. The only draw back is, you need to have enough light to keep them off when there is no train. When my head or hands blocks the light, they go off!

    The last way I know of is to use magnets. There is a specail magnetic reed switch that Walthers sells. You will need to glue magnets under your rolling stock. As the rolling stock rolls over the magnetic reed, it pulls it close. This allows current to flow.

    You can make these little circuits or buy them. Just alittle electronic and soldering skills. My personal opion is to use the IR's. They seem to be more realistic when they are operating.

  4. 60103

    60103 Pooh Bah

    One of our guys made the cheapest detector -- requires a photocell and an LED. Photocell is set between the rails and wired to the LED at the control panel. LED is lit until something covers it.
    OK, it has limitations, like it only works exposed to room light. He uses it for a short siding at the far end.
  5. Ben H

    Ben H Member

    NO - you could put a separate light in a tunnel or above a section of hidden track and it would work the same.

    Light covered and you have detection.
  6. jdh

    jdh Member

    thanks for the input! :)

    ok, so far we have:

    1 removed twin-t
    1 ir
    1 cds

    another thing you can do for the ir types, offset the emitter from the receiver across the track so you won't get a bounce between cars.

    you can do this horizontally [easier] or vertically [more of a pain].

    the vertical method could be done in tunnels ok, on trackside under a signal bridge [or any other bridge for that matter].

    i am leaning toward the ir method at this point since i run a lot in the dark/low light [makes my scenery look better] ;)

Share This Page