Re: Automatic Train Control
Vollrath, Don <dvollrath@...>
re - position fedbacktoggle quoted messageShow quoted text
2 or 3 possibilities:
1) Use electrical current detection at separate sections of the track from loco/tram occupation and/or each car. break track up into insulated detection blocks. Detect small current drain at each block. May require conductive axles on each car. Occupation detector output signals report back to master computer or local signal operating apparatus. Requires insulated rail gaps & electronic current detectors for each block.
2) Use magnetic passage scheme with magnetic reed switches at specific points along the track path. Tram and or cars have under carriage magnets to activate switches. Since switch activation would be momentary, master computer must keep track of which switch is being passed and direction from last detection. A "spot" location sensor like this is useful for a specific location, like crossing signal activation. Magnets attract 'metal dirt'.
3) Optical version of #2 with visible or infra-red light beam. May operate as across-track blockage type or reflection of beam off side or bottom of rolling stock. Simple opto-sensors use train shadowing of room light and therefore won't work in the dark. Some electronics required either way. Could also use ultrasonic detectors in similar fashion.
4) Use combination of scheme #1 with #2 or #3. Place optical sensors at both ends of electrical detection blocks. Diode couple signals to 'Wire-OR' the block end sensors with the output of the track current sensor for that block. Now block occupancy will be detected as loco with current draw has left block but rear of train is still occupying the block without need for conductive axles on rolling stock (!).
The above schemes will work with DC or DCC with proper choice of apparatus.
5) For DCC only, use Digitrax or other brand transponder idea. Requires: a) insulated track blocks with transponder type reciever wired to each block; b) transponder in each loco/tram or car to be detected; c) computer to gather transponder indications and keep track of train/tram locations. Available equipment is brand dependant.
6) Track current detectors also come in many flavors. Some work with DC, some only with DCC, some can do both. Some are isolated from track power, some not. Many have universal 'open collector' type outputs and can be used with 5V or 12V signaling. Some are 5V only. Be careful to pick the right one.
My choice is #4 with track current sensors and reflective type IR spot sensors.
Your automated tram application would be greatly simplified if you provided a reversing track loop at each end of the display rather than having the tram actually run in the opposite direction.
re - crossing signal activation
Your requirements are not too difficult. Requires 3 short block occupancy sensors at grade crossing to detect train approaching from either direction and to detect when it leaves the crossing island. Simple logic and timers do the rest. If you have computer, use that to perform logic and provide bell sound. (Bell doesn't remain ON when gate is down??). Check Dallee electronics (and others) for commercial equipment. A couple of '555 timers cam be made to do all without a computer. See future article in Clear Block.
[mailto:WiringForDCC@...]On Behalf Of Jan Frelin
Sent: Thursday, July 14, 2005 4:17 AM
Subject: Re: [WiringForDCC] Automatic Train Control
We're still considering a DCC solution, not in the least because of the
opprtunity of controling some accesories with the computer while you're at
it. Thus I have some followup question to this list:
1) What are the options for arranging feedback regarding stock position
with DCC? The basic scenario is still a tram going back and forth between
2) We require a pair of working crossing gates, which need to do the
following: a) start ringing bells to warn traffic. b) start closing 10
seconds later c) grow silent when down d) open silently. An interesting
automation project. Any ideas?
At 11:18 2005-07-01 -0700, Mark Gurries wrote:
Friends,Nothing is simpler or more cost effective than a DC solution.
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