Train detection

[wdcrvr]

Hi

I am trying to add a turnaround wye to a corner of my HO DCC layout.  One of the three legs of the turnaround will go straight into a corner of the layout.  I will be using a wye turnout (switch) at the entrance to that leg.  The idea is that a loco will enter the wye from one leg and disappear into a mountain.  Then the turnout is switched and the loco backs out onto the other leg.  Is there a way to detect when the loco passes the turnout on the way in, if the turnout is not visible?  Or a way to detect when the engine reaches the end of that track inside the mountain.

Any suggestions?

wdcrvr

[maxman]

Yes, I'm sure that there are multiple ways to do this.  One way would be to use what is called a block detector.  NCE makes one such device, called a BD20: http://www.ncedcc.com/component/virtuemart/?page=shop.product_details&flypage=garden_flypage.tpl&product_id=63&category_id=16.  Other vendors make similar products.

Basically you'd run a track power connection to a section of that tail track.  One of the leads makes a couple turns through the device.  The device coil senses the current and will output to either a relay or directly to a LED.  You would have to locate a sub-block toward the end of tail track (where the power leads through the device connect) so that when the device detects the engine it is far enough into the stub track to clear the turnout. 

[gondola1988]

Just put a plastic rail joiner on the track just past the turn out and when you hear the loco stop flip a toggle switch to apply power,reverse the loco and bring it out on the other leg of your wye. Just make sure the power is off when the loco enters the mountain and enough room for all the axels to clear the turnout, Jim.

[cacole]

Instead of a block detector, a microswitch with a long actuating lever, connected to an LED or light bulb, can provide a visual indication, or even activate an audio alarm.

Mount the switch in such a way that the loco will brush against it without catching on any detail parts.  These types of switches require such a small amount of pressure that it won't damage the loco.

All Electronics' catalog number SMS-196 or SMS-248 are examples of what to look for.

http://www.allelectronics.com/make-a-store/item/SMS-196/SPDT-SNAP-ACTION-SWITCH-W/LEVER/1.html  

[BroadwayLion]

LION has many tracks upon which a train must terminate and revers direction. A wye is only one such application. The LION cuts a gap in one of the rails so that the entire train is in the station (or in the mountain or whatever).  This is bridged by a diode (rectifier) so that only an out bound current will be passed to the train.

Train arrives and stops, when the switches are set for the outbound track, it is again powered.

I can do the same on sidings. The siding is gaped and so the train stops when it is fully into the siding. When the exit switch is aligned, it applies power to the section that the train is on and it proceeds. No rectifier needed in this situation.

LION runs his whole layout from the interlocking plant. The position of the switches will let the train move or not as the case may be.

ROAR