Innovations in Electronics

Grade Crossing using a Dream Player
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What do you do with a high-quality audio player that can be triggered by Block Occupancy Detectors (BOD)? Well how about a grade crossing complete with moving gate and stereo sound! Yes I know there are products available for this purpose, but how many of them allow you to put your own sounds in using stereo wav files on an SD Flash card? Whether or not you see the utility in using a Dream Player for a grade crossing, it is a nice application to show the Trigger Inputs, and Control Outputs. Plus you will save money by not having to purchase a grade crossing controller. Use that money to put real stereo sound on your crossing!

This application is really a combination of the BOD and Tortoise Driver described in other Bob's Bench issues (Dream Block Occupancy, and Dream Tortoise). You can see them by clicking on the titles on the left side of the screen. I won't review those applications here, we will just hook it all together.

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The BOD simply feeds into the Trigger Inputs on the Dream Player. On my test track, I cut gaps in the rails to isolate the sections for the Team Digital DBD2. I only need one section of BOD to trigger the sound and the gates, but since the DBD2 has two detectors, I wired them both up.

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For the crossing gate, I decided to use the Circuitron Tortoise. The Tortoise requires the power to be reversed to change the motor, or in this case gate direction. The Dream Player needs a little help for that in the form of a relay. Here I have wired a polarity reversing crisscross on an external DPDT relay to allow the Tortoise to go up and down. An external power source was used for the Tortoise to keep the audio clean of any motor noise.

Ok, now we have our inputs and our outputs, well except for the sound! We need a nice sounding Crossing Gate Bell. A quick trip to the sound effects library here yielded a crossing bell sound. As with most sound effects, it needed to be edited and trimmed to loop without making bad noises. I used Nero wav editor for this task. It isn't the best, it isn't the cheapest, but I use it sometimes for this task. If you are interested, it costs $80 to download it but it includes DVD burning, CD burning, DVD computer backup, a wav editor, MP3 encoder, video editing, and some other stuff I've never used. I originally bought it because I wanted to back-up my computer to DVD-R and Nero looked like a good solution. Check the link on this page to see the latest from Nero.

Now we have our wav file, just copy it onto an SD Flash card, and pop it into your Dream Player. The Dream Player uses the file name to associate the wav file to a Trigger Input, so don't forget to rename the file. In this case we are using Trigger #2 as our grade BOD input, so the file is renamed to "2-Grade Crossing Bell.wav". The "2-" indicates that this track is to play when Trigger Input #2 fires. Great, we have a bell, but the loop in the wav file only has 4 clangs for a total of about 2 seconds. Not much of a crossing bell. The Dream Player can loop on a dime, which just means it can repeat playing the same track over and over as long as the trigger input is active. To activate this playback mode, make sure DIP Switch #3 is in the "on" position. This mode will loop and play a track until the Trigger Input is gone, and then it plays the wav file until it finishes. That is why the loop length of 2 seconds was used. No matter when the BOD stops detecting the train, the most the Dream Player will do is play for another 2 seconds.

I'll be writing some more of these Bob's Bench installments, one of the next has to be how to edit a wav file to make a loop. It really isn't that bad, but until you practice, it can take some time to do properly. You might want to check out the Layout Sound Yahoo group, a link is posted on this page for you to check out.

Click to play movie

I shot a video of the grade crossing in operation so you can see what it looks like. Just click on this picture, and a video will play. Be prepared, it is a 1MB file in Windows Media format.

Bob Scheffler

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