I’ve had a few inquiries about the Arduino-based system I built to automate my two-track staging yard. It’s an extension of the home-built DCC system I made to run my railroad, the details of which are here: http://cs.trains.com/mrr/f/744/t/253905.aspx. I wanted to be able to run a train into staging without having to stick my head behind the backdrop to keep an eye on it.
In this part, I’ll be outlining the hardware used and in part two I’ll be covering the program logic.
Hardware
The system is driven by a Crowduino, which is essentially an Arduino Duemilanove with a built-in socket for an XBee wireless module. I used XBees when I was building the DCC control system, and had a spare one left over. So I decided to use it.
In the above photo, the XBee can be seen between the Crowduino (red board) and the shield. I usually use a prototyping shield to connect the layout to the Arduinos, as this makes it easy to remove the Arduinos for maintenance.
The XBee is configured with identical settings to the ones in the DCC throttle and base station. This allows for communication between the devices, and this will be covered in the section on software.
These components are mounted in a box on the corner of the layout, next to the staging track. The lid of the box is just screwed shut, so I can easily access inside.
In order to determine if a train is entering staging or not, there are three sets of sensors installed along the staging track. The first is an optical sensor just behind the gap through th
Very nifty. Sort of what I had been working on for my old layout, with 2 indications per staging track - clear of the turnout and train on the track. I was getting fancy, since I only had room for 2 tracks but they could be very long, I was trying to do serial staging with 2 trains on each track, so I had 2 sets of sensors and 2 sets of indications per track. I sort of had the logic worked out but then I never got much firther - I was doing it with PIC then.
I assume the bar graph is only approximate anyway, unless your trains are all unit trains with the same length cars in every consist. You could make it fancy and put a vertical bar | on each end of the = signs so it’s like a brakeman bringing his hands together to indicate distance. Or fill in from the right to the left rather than erase = signs, to show the train filling up the space. I’m thinking your code is somethign like:
<start, no train> bars=20
bars = bars -1
You can flip it around a couple of ways, either by using the ability of the LCD library to address a location, which you calculate based on the sensor return, or by using a display string:
(all this assumes the max is 20). SO as the scaled response from the ultrasonic sensor goes down, the number of blank spaces at the front (left) of the string goes down and the number of = at the right side of the string goes up. Or you could start the emptry track as a single | to indicate the bumping post and add the 20 spaces and = to that. So you’d get somethign that appears on the LCD like this:
I’m not sure what you mean by the bar graphs being approximate. The trains go into staging locomotive-first, so the ultrasonic sensors are measuring how far the front of the locomotive is from the end of the track.
With regards to the bumping post idea, I do like the sound of it. However, that would decrease the resolution of the bar graph, as it would have to take up one of the characters used for the graph.
What I mean is that while the bar graph may be proportional to the distance remaining, it doesn’t indicate actual cars (unless yoour trains all have cars the same length and you can calibrate it for number of cars). Dropping 1 out of 40 in the resolution isn’t that much, and the functionality would be the same, the less space between the train, represented by the = signs, and the bumping post represented by |, the closer you are to hitting it. Just how close when that last space disappears and the display is |===(39 x) depends on your calibration of the ultrasonic sensor in your code. I know they’re not super accurate, but depending on your scaling factor in the analog read, that last = could mean 1 more car length, or it could simply mean “stop now” Maybe one and the same if you have momentum on the locos.
That’s correct, it doesn’t represent the number of cars remaining. It’s an indication of how close the locomotive is to the end of staging. Generally, I need to stop when it gets down to about 6 of the = signs remaining.
Car length and train length come into play with the second set of optical sensors. If those are still blocked when the train has stopped, then the clearance point between the two tracks is fouled. In this case, the system will display an indication that this is the case, and will not cut power to the tracks until the train has been moved.
My layout has been designed to accommodate a maximum train length of 100 feet (i.e. 5 x 20-foot freight cars), and the staging tracks are long enough for such a train + my longest locomotive (the 4-4-0).
Well there you go then, losing one of the = signs to have a | sign to represent the bumper at the end won’t really impact anything. I was pretty much saying to use the | for the bumper if you reverse the = signs and have them represent the train moving onto the track - so as the distance between the train and the bumper got smaller, the blank space would go down and the = signs would fill in from the other side. Like I drew in my first response. Top to bottom, would be the train moving in. Still with the secondary sensor to indicate the clearance point. Same as before, just slightly different graphical representation - when you get down to 4-5 spaces between the | and the left most =, and the clearance indicatore is saying you are clear of the turnout, you can stop.
I only look at the UI this way because to me, an = indicates somethign is there whereas a blank tells me nothing is there. So as more of the train is on the siding, there is less blank space and more ‘something’ like the =. You can even make your own characters for those displays, but the character resolution is too small to make a decent little train symbol.
And in all my examples I’m assuming the bumper is to the left and the turnout to the right, so as the train backs in to the staging track it’s moving right to left. If your reality is the opposite, that may be causing confusion with my examples.
Just an alternative way of doing the display, with a couple of extra lines of code. Though more critically, it may need some 40 bytes more RAM for variable storage, which, with a mere 1K limit, could be an issue.
My concept for the previous layout wasn’t even going to have any sort of graphical indication, just a couple of LEDs for each spot and 3 sensors. One right by the bumper, the "stop NOW or else!, one for “you’re close (couple of car lengths)” and one at the clearance point on the other end.
My staging plan for the new layout is mostly concentric loop t
In fact I threw a small kit of parts like the IR emitter/detector pair used in Steve’s Arduino Speedometer and the ultrasonic module like yours, along with one of my Nanos and a breadboard in my bag to take on my business trip coming up as something to do after hours in my hotel room. For driving trips I usually take my toolbox and some model kits, but for flying - a little box of Arduino parts fits in my luggage quite nicely.
