The Arduino Z-Scale Trolley Project.

Yes, I suppose I forgot the mention the layout base. I’m using a 6” by 24” birch wood painting panel made by US Art Supply with the 1-1/2 inch deep base. They have a variety of other sizes. I have also purchased panels from American Easel for past projects. They sell a 24x48 panel which is great for starter layouts. I made a N scale layout for my kid with one of those.



Inspired by John Cubbins wood veneer tutorial, I ordered some walnut veneer to put in the ends of the layout.

https://www.raildig.com/raildig-build-projects/diorama-fascia-wood-veneer/

Except I used the iron on, heat glue kind. It worked about the same.

This is it before staining:


I then stained it with similar-transparent dark walnut stain, and it turned out much darker than John’s ebony on red oak. I then sealed it with polyurethane.



I also bought a better potentiometer. The first ones I got said they were linear, but the one I was using had poor useable range. The new one is a B103 that says it’s made by Cosmos Tokyo, but was sold as a “Taiss RV24YN20S 10K”. I like this new one much better. I can see from the serial monitor that it is much more accurate.



-Matt

 

Ok, I have updated the code to move the analog sensors over to the digital inputs. I added code to support an optional display and a optional small vibrate motor to auto correct stalls when the train starts. I also reconfigured it to support multiple layout types. So you can configure the code by setting the layout type and number of stations, and it will operate the layout appropriately. Instructions on how to change these configurations are in the code: https://github.com/Wonruc/ZScalePoint-to-Point

The code by default supports 4 stations on pins D4, D5, D6, and D7. This could be expanded utilizing pins D2, D10, A3, A6, and A7. Drop the display and you could get A4 and A5 too. As the Uno motor shield has D5 and D6 inputs, I used those for stations A and B. So now the basic setup for an uno system looks like this:


I got everything put together on mine and it is operating well.


Here is the vibrate motor. It actually works pretty well to correct when the trolley occasionally stalls when it stops or starts at a station, just to give it a little nudge.


Here is the diaplay I used, a white Hiletgo 128x64 pixel white oled I2C display connected to pins A4 and A5 for the Uno/Nano. I also got a layer of dirt, track painted, and ballasting done.


-Matt

 

Now for the display, I created some little images to show what the layout is doing so that you don't need the serial monitor to diagnose issues.

At Station A


Going to Station B


At Station B


Going to Station A


And, Something is Wrong:

 

So Matt, how does the pager motor help to prevent stalling?

Matt

 

It is not to prevent a stall, but to correct for a stall. And it surprisingly works well. It went from something where the trolley might go in 20-30 cycles before it would get stuck at a station, to where I come back hours later and it is still running. It is the same as me physically tapping the layout to get a stalled train moving again. And really this only happens while the train is departing a station. This vibrate motor is small and not very strong. This works because this is a tiny layout. On a much larger table, I suppose you could use a larger vibrate motor, or even a solenoid to tap the table, but the same concept could be used to automate table bumps.

The trolley runs fine most all the time. The code has acceleration and deceleration feature to it, and so when you are at the slowest speeds at stops and starts, all trains tend to stall more under those conditions.

But I also have the current sensing code for short protection, and I utilize the current reading to detect stalls. The current is a noisy reading. At high current, this noise is because of the PWM to the track power, and you have no practical control over when you sample the signal (at a "on" or "off" of the PWM). To overcome this, I sample the current 50 times and report the highest reading detected. One sample is taken every 10 ms. With 50 readings, one every 10 ms, the current value is updated ever 500 ms.

How the stall detection is working, is when a train leaves a station, the current should spike as the train starts moving. After 1000 ms (two current reading updates) after the train should depart the station, if a current spike above a 5 ma threshold is not detected, the code turns on the vibrate motor for 1000 ms to bump the layout.

Unfortunately the OLED display is causing me some feedback issue causing low non zero readings in the current sensor (Usually 1-2 mA). With the display removed, and a true stall, the current sensor reads 0 with no noise. So without the OLED display I could modify the code to detect 0 current at any time and auto-bump the table to get things going, but for now, the solution to detect the motor start current spikes works well enough.

 

Thanks for explaining, Matt.

 

I noticed you have ballast down now, Curn.

Got an updated pic?

 

Yeah. I was going to wait to get more scenery done. I seem to have misplaced my static grass applicator, and a better new one is one the way. I may have thrown my old one away on purpose to force me to get a better one, and then forgot about it. It was a cheap one and didn't do much, so no big loss.

The ballast I used was Arizona Rock and Mineral Z scale Pennsylvania RR ballast and the dirt is their Low Desert Soil. I had stocks of these, and I like the way the look. Track was painted Mission Models Dark Rust and ties are Rotbraun RAL 8017. And I remembered how to do Focus Stacked photography.

 

Lookin' good!!

 

Great project, but I wonder why you have connected the potentiometer like you indicate in the schematic. The "normal" way to use a potentiometer is to connect the ends to +5 V and GND, and the analog input pin to the slider. Then you will have a value og 0 to 1023 on the arduino pin when you do a digitalRead and can map the values to another range if you want. And if you need any "specialities", you can manage that in the code. Just wondering

 

You are correct.

As far as the potentiometer wiring goes, I copied that directly from this video at 3:20:


It worked so I didn't put much thought into it.

And looking at the comments a few others noticed the same issue you have, however the configuration does provide a 0 to 5V (or a ~ 47 to ~1022 mv reading from the analog input) where counter clockwise is low and clockwise is high. Although I'm sure things are flowing backwards through the potentiometer than how it is intended to work.

But according to other documentation, the outside pins should be GND and +5 V and the center should be signal, and no resistor is needed when using a 10K potentiometer.

I'm not sure what the 470 ohm resistor is for. A quick look at other projects, it seems to only be used when directly powering an LED through a potentiometer to limit current going through the LED. So for this project it would be irrelevant.

I will update the gethub to removed the resistor, and re-arrange the wires correctly. I appreciate the catch. Like I said, I'm an armature at this.[/URL]

 

I wrote digitalRead in my post, the correct should be analogRead.

 

I got the bulk of the scenery done. There is one big thing I haven't done and I'm not sure if I'm going to. I haven't done the catenary, mostly because I'm not sure how to make good period appropriate catenary. The Rokuhan and Marklin ones are too modern. To do it right, to look right on a rural railway, it would be toothpick power poles, with wooden arms holding a single electric line out there. If anyone has ideas on what to use for the wire, I would love to hear it. I thought about using a single line of piano wire. It needs to be robust, because there is no keeping people from touching it.

I made some little stations out of kits from Mike Basher, who sells these laser kits on ebay (Miata Mike). He is using a paper laser material similar to arch-stories, and they build up well. I used his loading dock kit and a speeder shed kit. Both turned out well, took paint well, and were easy to build. The instructions are pretty much all text.







The ground cover was build up in layers on top of the dirt/rock ground cover. Basically, I work in sections, putting down a layer of white glue, adding some grass tuffs(Late Summer Green 2mm Tuffs), a light sprinkling of ground ground foam, a sprinkling of green 2mm (I think late summer) static grass, then some WS harvest gold static grass, and last some Heki winter or prairie (HK3363) static grass. This gives the grass an early/mid California summer look where things are starting to dry out, and the tops of the grass are drying out, but the bottoms of the grass is still green.

Trees are Scenic Express SuperTrees, which is a sagebrush like plant material that you typically dip in diluted mat medium and then sprinkle ground foam on. Rather than dipping them in the mat medium they recommend, I just sprayed them with 3M super 77 spray glue and sprinkled with foam. I have also used hairspray in the past, but this 3M spray glue, the foam isn't falling off with handling, so this is my new preferred method.

And of course, a video showing it operating:



-Matt

 

Matt,
The module looks great!
Nice work on the buildings and Beautiful grass work!
Thanks for the video and explanations.

Scott

 

Very cool!!

 

Great work on that, too cool!

 

Love this little layout / diorama.

For catenary wire, maybe use ez-line?
https://berkshirejunction.website/ez-line/

Matt

 

I like it a lot! I like the way you trimmed it out too!