The recent Amtrak tragedy has me thinking is there an electronic way of enforcing speed limits over sections of a layout. I know that with DCC I can set a maximum speed over the entire system but what about indivdual blocks? I can see this being of particular value in a club environment. One idea I have is using on resistors each block to set a maximum speed. Of course this would involve some trial and error to determine the correct value. My question is I know this Idea will work on a straight DC system but what about DCC which uses a costant voltage. Any ideas?
Joe Staten Island West
The decoder sends a constant 12 volt pulse to the motor. Varying the width of the pulse is needed. That is how the speed of the motor is varied in DCC. Decoders do not send DC voltage to the motor. A meter would show DC voltage but a Scope would show pulses.
The decoder would need some input from a detector in a certain block via the control system.
You cannot lower the DCC signal on the track.
Rich
If you ever fall over in public, pick yourself up and say “sorry it’s been a while since I inhabited a body.” And just walk away.
I'm sure it could be done usung some type of automatic block that shuts the power off if the signal is red--I dunno maybe a computer interface perhaps?
Larry
Conductor.
Summerset Ry.
"Stay Alert, Don't get hurt Safety First!"
Some kind of speed detection would be needed in the block with feedback to the controller.
I believe I could program the CVs on my switchers indivdually to enforce a yard limit. but what about mainlines?
Many decoders today provide two-way communication - RailCom being one of the common ones. This two-way communication can be used with detectors and computer software to create these effects.
Mark.
¡ uʍop ǝpısdn sı ǝɹnʇɐuƃıs ʎɯ 'dlǝɥ
richg1998Some kind of speed detection would be needed in the block with feedback to the controller.
processors are often used to replace mechanical or electro-mechanical system components providing the same behavior, albeit less expensively. But often the capability of the processor is under utilized. DCC provides a throttle control. We often say speed control but it's only relative speed, not absolute speed. Step 10 on each decoder is not the same scale mph on each locomotive.
I agree with Rich, that if there were some mechanism to measure the speed of the locomotive and incorporated into the controllers, the throttle setting of controllers could actually be used to control the absolute speed. In other words, speed step 50 would actually be 50 scale mph (if possible)
Presumably some centralized processor can be used to make speed measurements of locomotives on the layout to calibrate their speed settings. If the DCC throttle settings could be interpreted as scale mph (i.e. 45 means 45 scale mph). If these speed requests are then passed through a similar centralized processor, limits could be imposed or various blocks. In other words, the centralized processor might receive a request for speed setting 30 (i.e. 30 scale mile per hour) but limit the commands to the decoder in the locomotive so that is runs at only 20 smph.
speed restrictions could also be set based on signal settings.
The gas pedal on a car controls the flow of gas into the engine. We then regulate as we go up and down hills to maintain the speed of the car. With computer control, it could be used to set the speed of the car, letting the computer control the gas flow to achieve that speed (similar to cruize control).
greg - Philadelphia & Reading / Reading
This sort of thing is easy to do with things like the DSCC BitSwitch - it is triggerable to send a broadcast STOP to the decoders, you ties in a relay with the signal system so that the block ahead of the red gets fed with the normal DCC signal if the signal is green or yellow, if red, it gets fed from the DCC BitSwitch, sending the stop signals.
It's not much more complicated, really, to make a device that boradcast s a constant speed step 10 or something, to force slow orders, or force a slowdown to restricted speed, along with the next level up send the stop. Green = fed normal DCC signal from the system, yellow, gets fed teh slow speed generator, red, gets fed the stop generator.
I'm kind of surprised there isn't more of this out there, it's not rocket science and it's compatible with all decoders and DCC systems. No feedback needed. Just detection and (optional) signaling - though without signalling it wouldn;t be fair to the engineer since how would you know to cut speed or stop if there were no indications to follow?
As for monitoring speed - just break up each block into two segments. There are existing speed measuring scripts in JMRI - couple that with some logic to open a throttle (also already in there) and override the set speed. You know what train is there using the train tracking scripts - RR&CO also does an excellent job of tracking trains with no transponding or other complex stuff that only sorta works.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
While this may be an interesting concept, I'm afraid I don't see a necessary application. Use at a club? What for? Just take the throttle out of Lionel-Louie's hand and tell him to go home.
Automation?
joe323I can see this being of particular value in a club environment.
the Pacific Southern RR club, which uses DCC, has "stopping blocks" at the ends of blocks. A stopping block is used to detect that an engine is about to run a stop signal into an occupied block or turnout and power is "cut" to that block until the signal clears.
this avoids derailments and collisions
gregc joe323 I can see this being of particular value in a club environment. the Pacific Southern RR club, which uses DCC, has "stopping blocks" at the ends of blocks. A stopping block is used to detect that an engine is about to run a stop signal into an occupied block or turnout and power is "cut" to that block until the signal clears. this avoids derailments and collisions
joe323 I can see this being of particular value in a club environment.
Back in the day, the real railroads used a system called Automatic Train Control, or ATC, on many major passenger routes.
If a train ran a red absolute stop signal, the throttle was "nuetralized" and the brakes applied. This system even worked on steam locos.
My DC control system has a version of this that works the same way. If a train runs a red sginal, it just stops dead in its tracks. It does not get "taken over" by the throttle controlling the next block, it does not run wild. If your throttle does not have the next block, your train simply stops - and here is the best part, this techno marvel is a free feature of the basic design of my system.
Sheldon