Crash Avoidance

"Hi Dale:

Thanks for your feedback.

I had considered adding a resistor into the NO. circuit when the relay is energized to drop the voltage to the track block instead of shutting the block off altogether.  This is a variation of the Lionel “preserving reversing without locking out the e-unit” procedure which would allow the TMCC loco (or any other loco) to come to a stop without shutting off.  But when I asked a question about the feasibility of doing this on another forum 10 or so years ago I was told that doing that could damage the TMCC electronics.  What do you think?

Bill"

Hi Bill

This can be done. I use a series of bridge rectifiers as voltage droppers instead of a resistor,so the minimum voltage at shut off is around 5. However for mandatory stops for collision avoidance this can get sticky because stalling voltages vary among makes of engines. In this case I found it is better to pull the plug especially if the train sits a while. Also when first starting a session the TMCC type engine would have to be cycled. This would be a bit tedious.

Here are pics of the relay boards and timers I use for soft start/stop and train routing. 3 trains run on a loop but only one at a time to reduce competing sound systems. I have 5 loops. You can click to enlarge. In the first pic you will see the diode and bridge rectifier voltage droppers. The train accelerates in 10 speed steps. The bell whistle function is also automated.

Dale H

Dale, you are clearly the king of conventional running, that's quite a rig.

Here's another idea. When running with DCS, simply press the green ENG button, then under the S3 softkey press ALL. All active engines will run at the same speed and will (hopefully) stay the same distance apart.

Or you can press the red button, they'll surely not crash in that case!

It reminds me of an old skill game/pinball/vending cabnet, or an elevator relay control panel. 

That's the only places Ive seen so many relays in one compact grouping. Nice, if I had enough different wire colors available that would be me too. I hate the number stickers.

Electro mechanical command control.

COLLISION/CRASH AVOIDANCE SYSTEM DESIGN:

I am working on a crash avoidance system. I use multiple blocks and block occupancy sensing so that I can tell if a train is approaching another stalled or derailed engine or uncoupled cars on an adjoining block.

This system will be used where track visibility is a problem especially in tunnels, etc.

This will involve the use of a combination of interlocking relays, MTH ITADs and high current diode strings for occupied track detection. 

The objective is to warn the operator of a potential collision using a visual and audible warning. I will make no attempt to automatically stop or slow an engine via the DCS system. All I need to do is detect the presence of a locomotive or car on a section of track and if an oncoming engine approaches an occupied block the system will alert the operator.  I can provide a PANIC button that kills the voltage on the occupied block since ALL my blocks are controlled using indivdiual relays. This system does not rely on the DCS system although the operator can take corrective action via the DCS as an optional response.

I have not looked into it much yet, but the new Faller car system is using a "GPS" style system for car control, I would assume something similar could be designed for trains.

http://www.faller.de/App/WebOb...en/ecm.at/index.html

Anything "can" be done, but from what I know of the Faller system, it's pretty pricy.

I am sure you are right about that John.  Still looks like it could be cool if it works as advertised. After a little more research I see that the system is actually designed by: http://www.gamesontrack.co.uk/ and it looks like the original design was for trains.

Interesting to note that when you click on the Catalog and Prices link, it hangs.  I guess the website chokes on the prices!

It finally came back.  Of course, once you have the system, which ain't cheap, you need some pretty fancy software to actually make use of it.

Hi Dale:

Thanks again for the follow-up.  That is quite an impressive set up. 

But re using bridge rectifiers instead of resistors, are there any other advantages in addition to enabling stepping up of the speed in increments instead of providing normal running voltage all at once? 

Assuming I could determine a minimum stall speed for all of my locomotives, TMCC or Conventional, would it be easier to size the bridge rectifiers than it is to size resistors to arrive at a stall voltage?

And the last but most important question, any consequential damage to the TMCC electronics?

Thanks,

Bill

I fixed and serviced electromechanical pinball machines and juke boxes for 30 years so I guess it shows.

Dale H

First in conventional no damage to engine electronics should occur when running in conventional mode. Dropping voltage with diodes is similar to throttle manipulations,the sine wave is differently shaped but still symmetrical. 

Resistors in series will act according to Ohms law. Even the same train will vary in resistance as it accelerates. Even stall voltages vary,MTH PS2 is about 8 volts for example. 

Diodes however drop the voltage at a fairly steady .6-.7 volts regardless of load. (there is a slight variation but this is technical and not important in this application). So the voltage drop will be the same regardless of the make of train run or the speed of the train.

Bridge rectifiers are really just 4 diodes configured in a package. So when the + and - are connected they are 2 didoes one way and 2 the other and can be used as a voltage dropper.

Dropping voltage with diodes is described here

http://www.jcstudiosinc.com/Bl...=413&categoryId=

In conventional, just putting on or removing the voltage all at once is not very prototypical. It also stresses components. I see public layouts where a train just stops on a dime and all the light go out at a station. Poor passengers become frantic and you can here the screams from the cars. With my board it starts in 10 steps,the bell (if equipped) rings and shuts off as the train moves. Around step 7 or 8 the whistle sequence relays are activated,then reset on step 10. At a station stop capacitors hold in step relays so it takes about 12 seconds to reduce voltage to minimum. For mandatory block stopping I do not have the luxury of distance so I pretty much pull the plug but leave on 8 volts for a few seconds,then zero. 

In addition for forward only operation stall voltage at a station stop leaves on the lights of the engine and passenger cars.

Dale H