I’ve been doing quite a bit of PCB design these days, here is a version of my controller board, the ‘microwidget’. It’s quite compact. I have not had any made yet but I thought it came out really sort of, well, neat. Like art kinda.
All total I have about five or six small circuits for doing control networks- specifically for large scale model trains. DCC input and output, servo control, DC brushed motor control, reversing relays- all via Industrial strength Xbee Network wireless.
I’m also thinking of making an apt-get debian package to install JMRI on a RPi 2 and gitlab for my code. Hmm.
Here are the final two prototypes. The master obviously connects to the Prodigy Express and sports a long range antenna for max transmission power. What I’m thinking here is this is the module that will be connected to my RPi 2 which I am planning on running JMRI on. The Pi 2 will also have a long range wifi antenna on it so I can use it to source web pages to my phone and tablet. My standard handheld design is what I actually use to drive my trains with.
The second pic is the client. This one is fairly comprehensive and has quite a few parts but I use it as my standard prototype rig. In addition to the control board, it also has an (expensive) Pololu 18v7 motor controller and a current sensor. The DCC output stage is the board with the large chip beside the speaker. All it is used for in this incarnation is to drive the Econami Diesel DCC decoder which powers the speaker on the right.
Here are all the parts labeled, you can click on the picture for a larger version-
A diagram of what I’m working on. Not shown is my prototype battery powered handheld, it would be (in addition to or to replace) the master in this diagram. 300ft range between the master and any client node, 250kbs.
I have about 80% of this working as indicated. I’m still coding up the Client DCC output state machine. It’s almost there but I think I’m off one bit at the end of the message. Hmm. Also, I have not yet tested the LMD18200 driver that will power the DCC out to drive the decoder, so that’s another step.
The weak link to me is the purple arrow between the prodigy and the base station. Right now, I have the cheap express unit, so it’s that thick telephone sort of wire. But from what I’ve read the wireless unit only has about a 40 ft range? Not so good. That is where the proto handheld I’ve built will come in. But that’s another project.
The whole idea of all of this is to be as transparent and fast as possible. DCC in at one end, it pops out at the client with only a small delay. How small? I’m hoping 10ms or so but that’s probably optimistic and will depend on the traffic. Lots of experimentation and testing to do but so far so good.
So this is the trace. The upper signal is the generated DCC waveform out of the client microcontroller. The lower waveform is from the Prodigy Express. Same message, skewed a bit, the top trace is about 1.5ms to the left. Look carefully and count the pulses and consider the widths, see how they are almost dead on except for that last bit? Hmm. Oh that will drive me nuts until I fix it!
Here I’ve added the 1/8 inch square strips and the window trim, then I shot the thing with some light brown primer.
I’ve been doing some experiments with the CNC router, trying to cut styrene. I’ve messed up and melted a sheet or two but now I think I’m getting the hang of it. I’m working on a standard N&W depot, this one is at Winfall, VA. I found the pic on the Virginia Tech Photo Archive.
Anyhow, what I have found is that styrene needs to be cut with a slow RPM and a decent inches per minute feed rate. I’m using a 1/32 inch bit at 7500 RPM and a 25 IPM feed rate. You also have to cut shallow, anything more than say .030 or so will start the dreaded melt. So I do three passes to get through 1/8 inch styrene (.125 inches). This produces a big shower of nice plastic chips or ‘saw dust’. This is what you want to see.
I wired up my yellow critter with a control widget, a Turnigy 20A ESC and a 4.8v 2300mah nimh battery pack. Works quite well. I did have to add a relay to reverse the motor but that’s already supported by the software, it’s what I use in my RS3.
A pic from the video, out on the track at Gilbert Virginia.
Just can see the Xbee in the cab. The battery is in the engine compartment along with the Turnigy ESC. The relay to toggle the motor direction is also in the cab but you can’t see it from here.
The development platform for my Dash 9 whenever I get around to it. A close shot of the control board with the Xbee. This is the same control board in the Critter. There is just enough room (I think) in the critter to put in micro servos for the couplers but I have not gotten there yet…
And here is the critter with the handheld controller.
This is my newest critter design. A freelance sort of fantasy vehicle but it came out pretty good and was fun to build. A couple of 3D peoples and some resin cast details thrown in for good measure. Everything is cut out on the CNC machine except the fuel tank which is a piece of PVC pipe. (I cut those on the band saw). Anythow, I am planning on possibly selling these as kits or at least making the plans available, not sure how that’s going to work out quite yet…
One of my 3D printed 1/29 scale fellows on a CNC cut out Critter. Its a tiny locomotive I’ve designed based on a collage of prototypes from google searches. It’s cut out of sheet of 5mm finish ply and fits on a USA Trains 4 wheel power truck. I’ve left room for batteries and controls, I’m not a track power guy.