Photos of miniDCC in potato salad container

Here they are, I finally found some time to take some pics and upload them.
This is the first prototype of the miniDCC controller/programmer/booster
that I built. Wrong keyboard and all, but it seems to work ok. I have a proper 16 key keyboard now and a nifty project box I found today for $3. The IDE cable is pretty ugly, but I didn't have anything else handy. The second prototype will hopefully be much nicer.
http://i55.photobucket.com/albums/g143/afremont/DSC01217.jpg
http://i55.photobucket.com/albums/g143/afremont/DSC01218.jpg
This is the PIC board. It scans the keypad, drives the LCD display and also generates the DCC waveform that modulates the h-bridge.
http://i55.photobucket.com/albums/g143/afremont/DSC01219.jpg
http://i55.photobucket.com/albums/g143/afremont/DSC01221.jpg
This is what I call the "safety" board, it has several functions: 1) detects current overloads (shorts) and shuts of h-bridge if detected 2) monitors the DCC signal from the PIC board and turns off the h-bridge if invalid or missing 3) supplies 5V regulated to the PIC board
http://i55.photobucket.com/albums/g143/afremont/DSC01220.jpg
Here are pics of an Athearn that I converted to DCC, what a pain. Nice trains, but they use a real lousy track power distribution system IMO. I mean really, swaging the ground lug. Unplug the light support once and it's useless after that. I drilled and tapped a hole, promptly breaking a screw off in it. I then made another one on the other side of the chassis that turned out nicely. It's kinda big (4-40), but hey it's what I had on hand. ;-) I still have to add my lights and shrink wrap the extra wire.
http://i55.photobucket.com/albums/g143/afremont/DSC01222.jpg
http://i55.photobucket.com/albums/g143/afremont/DSC01223.jpg
http://i55.photobucket.com/albums/g143/afremont/DSC01224.jpg
You can see that my layout is still in the design stages. The floor is the biggest work area I could find. ;-)
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On 1/8/2008 3:46 PM Anthony Fremont spake thus:

Is that surface-mount thingy in the background the PIC? Comes on its own interconnect board? Looks pretty gnarly.
Say, has anyone here with this kind of experience ever tried other processors? Specifically, I'm thinking of the ones I'm familiar with, the SX series of micros (formerly Scenix, now owned by Parallax)? The SX-28 is a really compact little critter that's plenty powerful enough for a DCC application, it would seem to me.
Here's a link if anyone's interested: http://www.parallax.com/Default.aspx?tabid$8.
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David Nebenzahl wrote:

That would be the back of the LCD display. I don't do surface mount, this stuff is small enough. :-) The PIC is right next to where the IDE cable plugs onto the proto type circuit board. The other end of the IDE cable is to the LCD display. It's hard to see anything because of the wires.

I'm playing with ARMs now. They really honk at about 60 times faster than the PIC _and_ 32bits. I plan to b
I'm working on my new case now. Once I put it in that, I will take some more pictures making it easier to see what's what. The wiring will be a tad neater......and a little shorter. ;-)
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Looks good. The whole package doesn't look like it takes up much room at all, and it's maybe a couple hour assembly job. I like the "scrounger" and "hacker" (the good kind) look. ;-)
If you're looking for an 8-conductor cable, you may be able to snag some bad network cables. I used them in my Bachmann F unit rewire.
Thanks for posting the pics, I'll have to look in to doing one for myself. (You know, we might even be able to make the throttles communicate via TCP/IP...)
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Puckdropper wrote:

It's engineering; making what you want from what you can actually afford. ;-)

Last night I stayed up late and moved everything to a real project box with the correct keyboard. It looks loads better. I picked up some new wiring pigtails today at the local electronic junk store. Now the keypad connects with decent looking wiring that isn't wrapped in electrical tape. All tucked away inside a black project box and it looks almost presentable. I need to pick up some LED holders for the indicator lamps to finish it off.
One significant difference between the miniDCC controller and the Bachmann is the voltage. I'm using 12V (nominally speaking of course ;-) and the Bachmann was putting almost 18V on the rails according to my true RMS meter. Right now I'm using a 1.5A wall wart for power, I'm considering a switch to 16V or so since the circuitry should easily handle up to 20V.

I'll take some more pictures later if I get a chance. I'll try to show better detail and less mess. It was pretty easy to put together, but it did take me allot more than a couple of hours. It's slow going when building on proto boards. I spend allot of time trying to plan ahead as I'm translating the schematic into protoboard circuitry. With pre-made circuit boards it really could be a two hour project.
I got 128 speed steps enabled for the engines with TCS decoders. Wow, my athearn on clean track and freshly cleaned wheels will really crawl on speed step 2, even pulling a bunch of cars. I can't believe the motor will turn that slowly, must be the flywheels. Takes a while to slow down with all those steps so I've been using the emergency stop button more. Somethings wrong, I should be having a mid-life crisis but I seem to have skipped ahead to my second childhood. :-)
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Anthony Fremont wrote:
SNIP REALLY GOOD REPORT ON PROJECT
Somethings

Thats the spirit! Good for you!
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wrote in

*trim*
It is a bit of a trick getting wiring to look nice... I've done it once or twice. (The key is of course to plan, plan, plan.)

Are you measuring directly across the rails? There's apparently an AC signal on there that could confuse your meter. TCS or Digitrax (I don't remember which) recommended measuring the F0 output on a decoder and adding one volt.

Yeah, I noticed that. When I do mine I'll probably make the circuit boards myself, but I don't mind doing that. (It's a couple hour process in and of itself.)

Digitrax systems, at least, have a wheel that responds to how fast you turn it. In less than 2 seconds, I've got my locomotive going from speed step 55 to 0. Maybe your PIC code could do that if it detects the slow down key held down. Remember though, it does take real trains some time to stop!
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