Remote Control Audio for Rolling Stock

I can see encoding the data in the MP3 secondary channel, that makes prefect sense.  I'd probably not bother to try to make a full-up TMCC decoder, I'd just use a simplified serial decode.

One possibility is how I'm considering handling the TMCC option with the sound board.  I've pretty much decided that I can only afford to produce one main board and one set of master software.  If I replace the RF receiver with a simple board that just decodes the TMCC serial stream, I can use the RCDR receiver to receive TMCC and convert it to compatible RF receiver outputs.

If I replace the plug-in RF receiver with a small board with a uP and the audio detector/decoder, I could then simulate the command streams that would come from the RF remote.  I would just pipe the secondary channel audio that I've thoughtfully provided (with a little prompting), and feed it in as the input to that board.  That does beg the question of outside control, so I have to do more thinking on this.  I think whatever I'd come up with for this option would be an add-on somehow.

One problem with a project like this is at some point you have to stop designing and start producing.

BTW, in the previous post I had attached the .MP3 serial data test stream that I used in case you want to confirm it "works" OK on your MP3 player.  It's about 1/4 sec long or so.

Anyway I'm all for keeping the ball rolling so when to make the final boarding call announcement is obviously up to you! 

So at the risk of sounding like a broken record, I want to re-iterate the need for the layout-accessory version.  If you need to minimize the number of option boards, perhaps you could integrate direct pushbutton (or the like) switch input support on the plug-in board (used in place of the RF board).  Or maybe it's yet a 2nd plug-in alternative to the RF board.  Of course that could be designed later...but clearly the main-board software must be written to detect this board is what's plugged in or otherwise seamlessly support what it generates. 

And before I forget.  I meant to ask if you're making the rectified bridge voltage available as an output.  Since the 5V regulator has limited current output, I'd think this voltage would be useful for driving external devices.  Or at least this is how MTH does it on their PS2/3 boards providing the so-called PV outputs which is used to drive the motors, smoke heater, solenoids, etc. 

I'll take a look at your MP3 file.

I'm pretty close to "pulling the trigger" on the first prototype of the full-up board.  It's getting pretty stuffed now.  I keep doing trial layouts to see how things look.

I'm thinking along the lines of simply replacing the RF receiver with an board with the same contacts and the same interface characteristics, i.e. four data bits and one "ready" bit, it would obviously run on 5V as that's on the connector.  It would be a simple matter to use a cheap uP to simply convert what we're receiving to the RF transmitter looking outputs.  I think this could solve the problem of making a TMCC version as well, just pipe the serial TMCC input into it and turn it into the same RF transmitter interface characteristics.  It's conceivable that the TMCC board could also support the direct inputs, haven't given that much thought.  If I keep the same interface to the main board, I don't have to change anything in the main board software to change from TMCC, direct PB, or to RF input.

The rectified voltage is on the battery connector, but if we allow too much power draw from that, it would cause issues for the regulator as the ripple at lower track voltages would start to get pretty large.  When I have the full-up one running, I'll have to take a look at that.  The ripple when the current draw gets up around 300ma is pretty large now.  I don't really want to go to larger capacitors.  Having raw DC available isn't a big priority to me as it's easy to obtain from track power.  Another issue is the fact that it's totally isolated power due to the bridge, the careless user could decide to ground the negative and blow up the main board.  From seeing it happen to the ERR RailSounds Commander single board version, I can tell you it does a lot of damage, more than just taking out the bridge!  I can't idiot proof the board, but I can keep the users from making moves like this.

You'll be happy to note that I increased all traces to .008" and the power/ground to .012".  I couldn't go more as the autorouter couldn't finish, even moving stuff around.

LOL, can't wait John!

Stan, I'm kinda' glad I didn't go the first battery backup scheme we talked about, the little regulator board that is supposed to go from 2V and up to 5V has lousy regulation at 200ma.  It peaked at almost 5.5 volts when the input voltage was a full 5V, and it was down to 4.6 volts before the input voltage crossed 3.5 volts.  It only provided about 4 seconds of usable power from my 2.5F cap, assuming a diode drop as the configuration required.  The only good news is the diode kept the 5.5 volts from being a problem at the high side.

The switcher that's boosting the voltage to 9 volts is a better bet, it's regulation is better, and the output voltage isn't that critical as I'm regulating it again on the main board.

Dennis, my prototype boards for the full-up design are on order, and I have a few sets of parts for my testing.  I don't really know exactly when I'd have any quantity, I first have to finalize the design and testing, write the software, and get quotes on building the boards as well as the final parts lists.

I just got the second regulator board that I ordered on eBay, this one works MUCH better.  From 3V to 5V, the output voltage remained constant within .1 volts at 9 volts.  The test was done with a 200ma load on the output, which is what I'm guessing will be typical. The board didn't even get noticeably warm during the test, good conversion efficiency!

In an interesting, but not important to me characteristic, if you take the input voltage above the output voltage, this supply must tracks the input voltage.  Apparently, it can't buck, only boost.  No sweat, as that's what I want it to do.  It's $1.49 instead of $.99, but it works really well for the task.  It's also bigger, something I'll just have to live with.

What I got was eBay: 400921076826.

Got my PCB boards in, here's the conventional power add-on module, I built that up to test.  Of course, the switcher I ended up with has the positive and negative swapped, so my jumper wires swap as well, a bit of a kludge.  I also found out that the resistor to limit the inrush current is required, without it the initial charge current is 1.5A, more than the other components like the input rectifier can handle.  I just have to live with the longer initial charge time for the supercap, a 5 ohm resistor limits the max current to around 1/2A, about all I want to push it to do.  The switcher board is fairly large, but the package works great and gives me about 10 seconds of operation with a full charge.  I'll probably do another spin of the boards after testing is complete to clean up the leads and perhaps optimize the component placement to try to minimize the overall size.

Did you compare the larger stepup switcher with the original relative to the 10 sec operation time?  The original uses the MT3608 chip which switches at 1.2 MHz.  The larger board uses the XL6009 chip at 400 kHz which apples-to-apples means a larger inductor which is evident.  I don't think the 0.1V regulation is material since it is regulated by the 5V Recom.  I also think you'd see better regulation when loaded with the 100's of uF of load vs. just the bare MT3608 stepup module which has virtually no load capacitance; or maybe you did test the MT3608 with the intended load capacitance from the main audio board but whatever.  In any event, I think size matters in this application but obviously that's just my opinion.  If your final load is "only" 200mA @ 5V or about 1 Watt, I don't think this taxes either module. I suppose since the board is not complex you could add pads to support both without crossover/kludge wiring.

I'm going to try the other one, this was my first test.  I agree that the module is larger than I'd like, the big capacitor kinda' swells the size.  I tried it by shorting the resistor, way too much initial surge, it pegged the meter over 1.5A on my bench supply.  I think I'll try something like a 2.7 ohm resistor and see how that does.  Maybe a bit faster charge and still acceptable initial surge.  OTOH, the 5 ohm I'm using may be sufficient for the intended purpose.

My next push will be to assemble and test the main board, that promises to take a bit longer, quite a bit of software to exercise all the I/O properly.  I have to build myself a little test board to exercise all the stuff I have configured on the board.

I have what I'm hoping is the final version of the sound board in hand.  This is the version with all the bells and whistles.  I have to start with the software now, so it's really inert, but at least the PIC debugger recognizes that there's a processor, that's a good first sign.   The clearances also all appear to be OK, all the parts fit without a problem, and it looks like there's sufficient clearance around all the connectors to use them.  This is one busy board with all the connections, it's going to take some effort to get all the software running!

Looks like it turned out just great. That's a nice looking device. Hope the programming works out as well as the board looks, if it does you will be in business.

Guns,

   Looks like you are starting to get it together, keep us informed on your progress.

PCRR/Dave

It's nice to see the board done, but with all I have on my plate right now, I have to try to squeeze in the software job.

John,

I was just reading through this month's issue of MRH and was following the links to their advertisers when I stumbled across the CKT-SQUEAL User-Programmable Sound Player.

User's Manual

 

The latest ARD-LTC2499 hardware design files and source code are now available at GitHub

 

Hardware v1.1 Schematic

 

CKT-SQUEAL is made available under license from Nathan Holmes and Michael Petersen. The design is released under the Creative Commons BY-SA license, and the source code is released under the GPL v3.

I don't know if you are planning to make your design proprietary or not. According to the license, any modifications would also have to be released to the public as I understand it.

In order to fall into line with your project, a remote control device would need to be incorporated into the design. Also, the board runs on 8-14VDC. It does power a speaker 4 - 16 ohms, can be loaded with 4 separate sound files on a microSD card (WAV format) and has one-shot, random, looping, and beginning-middle-end playback.

I hope this helps your project and wish you the best for its fruition!

Mine is an all original design.  Obviously, I'm using the canned MP3 module and the canned RF transmitter/receiver.  The main processing board and the future discrete and TMCC interface to replace the RF receiver will be my design.

HI John

I just amazed how are able to answer question and still be able to do your project. I would say that you have to be the King of Time Management. How is the project coming along?

John I have been following your project, understanding a good bit but I sold insurance...nuff said.

Thanks for including all of us and best of luck with it. Really neat process and application. Can't wait to try it out.

Thanks guys.  With a couple of vacations and a wedding before York, right now it's going somewhat slowly.  I have lots of things pulling me in all different directions.  I have the hardware, and I've started doing the basic checkout, but I don't have operational software yet.

Hi John

I know what you mean about family and trying to build something. It is either you have the time or you do not. Right now I do not have the time but hopeful soon I will be able to finish my project, I am still shooting for Christmas. What is your time frame for completing the build? I would love to see what the final product will look like.

I'm still wanting to have a finished first cut for York, I'll probably try to have a couple of prototypes.

That makes sense to have it done for the York show. This way you reach the largest non internet crowd for this product, good marketing plan. Unfortunately I will not be able to go to York because my little one is still too young to go. His attention span is about 10 mins and he would get very bored very easily. I am planning on going to that show some time in the near future but not this year. Please let me know when you post the video on line I would love to see it.

Not to worry, I'll be sure to post it here on OGR.