Title
----- 
Safe Distance v1


Goal
----
If you have a track plan and you want to run two trains on the track, then
probably one train will go faster then the other train. Therefore you must 
build in a buffer between the two trains so that the trains will not crash 
into each other.


Solution
--------
On the track plan choose two places to create a buffer. This buffer must be
isolated from the rest of the track and will take up 3 or 4 track pieces.
The buffers are individually powered by the RCX and the remaining of the 
track is powered by a speed regulator. Put the light sensors just after
the buffers to detect the presence of a train.
When a train is detected by the sensor of buffer 1 it's allowed to pass 
through because the buffer is powered. After the train has passed 
completely the buffer is powered off. After a configurable delay, this is
the minimal time between two trains, the buffer is powered again. The same 
applies for buffer 2 which is controlled simultaneously. 


Bill Of Materials (for two buffers)
-----------------------------------
1x RCX
2x Light Brick
2x Light Sensor
4x Train Track Contacts
.. Electric Wire
.. Track Straight/Curved


Limitations
-----------
This concept only works with trains with only one motor. Also the motor must 
be the in front of the locomotive (the first set of wheels). If a train has 
a pulling loc and a pushing loc both powered, then the train will not stop 
on the isolated buffer because the pushing loc will still receive power from 
the main loop.


Tip
---
If you own a RCX with power jacket, then you could also use the RCX brick to 
power the main track. Advantage of this solution will be that 1 component 
controls the complete track plan and that the train will travel with the same
speed over the track and the safety buffers.



Stefan Sanders
StefanSanders@Wanadoo.nl