u/aengusoglugh

After reviewing this circuit with some people who know more about electronics than I do, I ordered the parts and the perfboard to build this circuit.

Gulp.

This will be my first series foray into electronics -- probably not much of a foray for some people -- but a big step for me.

I guess that's one of the aspects of this hobby that drew me in.

I really enjoyed learning what I think of as the electrical part -- using PowerPole connectors and crimping tools to build what seems to be a pretty reliable power system for modules.

I enjoyed laying track correctly -- figuring out how to do a good job of attaching Unitrack with screws from the bottom, getting everything aligned correctly so the module fit together well -- and after I take the layout apart and put it back together.

Now onto electronics.

I am nervous -- but not as nervous as I am about scenery. :-)

I now understand why it can take a long time to build even a simple layout. :-)

The T-TRAK standard -- as adopted by my local club -- specifies a 15 vac accessory bus. I want to rectify the power and use it for two purposes: steady DC for powering LEDs to indicate the position of the turnout, and a DCU controlled by a momentary SPDT switch.

Kato turnouts use a single bi-polar solenoid move the points, a momentary +- charge fires the solenoid in one direction, a momentary -+ charge fires solenoids fires the solenoid in another direction.

Voltage isn't critical -- people report success with anywhere from 9 vdc to 25 vdc. What is critical is the duration of the post is < 250 ms or so to prevent burning out the coil.

It would be simpler to use a DPDT momentary switch to control the turnouts, but the DCC Concepts Cobalt switch I want to use only one SPDT momentary contact -- it has two continuous SPDT contacts I want to use as a DPDT switch to control the LEDs.

Here is what I then the circuit does from left to right.

The 15 vac comes in at the left is rectified by RR1 (a bridge rectifier), and the C1 buffers that output.

J2 taps into the +20v rail and the ground to provide DC for LEDs.

The circuit to the right of J2 is the DCU circuit. I copied that from this RR-Circkits CDU Kato Swtich Machine Circuit. C2 is wired in series with L1 -- the Kato turnout -- through J3.

The anode (+) is of C2 is wired to the 20v rail, and the cathode (-) is wired to the SW1, the momentary SPST switch. SW1 is physically connected to the cathode, +20v and ground through J4.

When SW1 connects C2 cathode to the +20v rail -- cathode to the anode -- short circuiting the C2 -- C2 dumps its charge very quickly, firing the solenoid in one direction.

When SW1 connects C2 cathode to ground -- the anode is at +20v and the cathode is at 0v, the capacitor charges very quickly -- firing the solenoid the other direction. When C2 is fully charged -- which takes < 100 ms -- current stops flowing.

That gives me what I want -- a momentary pulse in either direction to fire the turnout.

This is my first attempt ever at design and drawing a circuit.

Does it look correct?

The inputs to this circuit are 16 vac, and there are two sets of outputs -- 12vdc CDU outputs for a momentary pulse to fire a bi-polar solenoid and steady 12vdc outputs to drive LEDs.

I am using this CDU Circuit from RR-Cirkits, and LCC Cobalt S switched to control the Kato model railroad turnouts. The Cobalt switches have three sets off contacts, two continuous (ie, on-off-on) SPDT contacts that can be used as a DPDT switch and a single SPDT momentary (ie, momentary-off-momentary) switch.

I intend to the two continuous SPDT contacts as a DPDT switch to control LEDs, one green and one red, to indicate the position of the turnout.

The single momentary switch will be used to control the bi-polar solenoid in the Kato turnout.

16vac will come in at the left end of the perfboard to an OTOTEC 16 vac to 12 vdc converter designed for use on model railraods. There will be a 2200 uF 35 volt filtering capacitor as per the RR Cirkits diagram. The steady DC output for the LEDs will be attached there.

The series capacitor that provides the CDU pulse will be attached to the momentary SPDT switch that will switch between the ground rail and the +12v raid to either charge or discharge the capacitor as per the RR-Cirkits diagram.

Does all of this look like it will work?

I do have a question about the OTOTEC converter -- there are comments that although the output is labeled "12 vdc", in fact there ahead been reports of voltage as high as 22 vdc.

Is there a better choice?

I would actually be happy with a 16 vac to 16 vdc converter, nobody seems to make those.

The first modules I wired were corner modules, and I didn't have a clue what I was doing. :-)

I built a 3 way splitter for each wire using PowerPole connectors and a single wire from the splitter to the terminal strip, and a module feed from the terminal strip to the pigtail.

They work just fine, but look pretty crazy -- and there are PowerPole connectors that will never be disconnected, so they are sort of wasted.

When I posted a picture of that wiring, someone -- maybe u/HomeyHal or u/bissacs? -- posted picture of wiring where the splitting was done with a terminal strip.

I tried that for my second set of modules -- and I decided that I really preferred a method of wiring where a terminal strip was screwed to a block of wood that was glued the bottom of the module. and the connection from track feeds to the module feeds is all via a terminal strip.

But since that set of modules was were crossovers -- and the rule of O&O is a Kato Unijoiner at every track junction -- there were still a lot of wires. I used a 6 position terminal strip for each wire, where one side of the terminal stop strip was a bus bar, and the other side had 4 track feeds and one module feed.

I liked the terminal strip splitters better than PowerPole splitters.

Finally, I am wring a single straight T-TRAK module-- which means two prices of track for the red line, and two pieces of track for the yellow line.

This looks pretty clean and simple -- and it was very fast.

Now I am trying to decide if I want to go back and re-wire my corner modules using terminal strips instead of scratch built splitters.

I didn't realize when I took the picture that my feet and my living room carpet were included.

But the fact that my carpet was included makes a point about on of the things I love most about T-TRAK -- I doing this wiring in my living room sitting in a comfy office chair with the module upside down on a folding table next to my desk and not one -- but two -- desk lamps focused on the work.

For someone of my age, that is one heck of a lot more comfortable than crawling around under a layout holding a flashlight in my mouth while trying to string wires.

This photo is from a pre-marked and drilled HO scale T-TRAK module.

Generally when I am screwing in track, I put a screw in one end and then the other because I can see the posts and the screws align at both ends.

Then I put screws in the holes between the ends.

Today, I was having a heck of time with the middle screws.

So I did what I do when there are no screw holes marked and I painted the bottom if the screw posts with a paint mark and fitted the track, then pushed down on the track.

The creates little paint donuts that show me where the screws need to go.

I don't know if it's clear from the picture, but the paint marks at the end of 369 mm piece of track area perfect aligned. If you look the upside down "S369 369MM STRAIGHT", then panted mark is centered right over the pre-drilled hole. At the other end -- the side of the module -- the donut is very closely aligned with the pre-drilled holes.

But the three center donuts are way off from the pre-drilled holes.

I wonder if the module kit was just incorrectly drilled -- of the Kato Unitrack has varied the location of the holes over the years?

Has the location of the the screw posts remained unchanged over the years in N scale Unitrack, so say piece of N scale Unitrack from 2015 woud have the screw posts in the same place as a piece of Unitrack from 2026?

Or has Kato moved the location of the screw posts occasionally over the years?

My layout is DCC, and I occasionally need a programing track -- so far only for setting locomotive DCC addresses. Technically, I think I could use POM (programming on main), but for the cost of a couple of pieces if track, I wanted a dedicated programming track.

I thought it would be very cool to have a siding with a DPDT to choose whether the siding was main or programming, or a programming track isn an engine shed, etc.

I finally gave on that because of space. I don't know whether this scales to N scale, but an HO #6 switch is nearly a single module width long, so a switch and a siding that could be used as programming track would require a double module.

My garage isn' that big. :-)

I also realized that I would use a programming track pretty infrequently -- as leas compare to a main.

So I ripped 2" wide or so piece of ⅛" plywood and built the programming track as a separate module.

How many of you incorporate your programming track into your layout? How many of you have a separate track?

I saw this picture -- and my guess is they really don't belong in my modern DMU Transit system. But I think that they look very cool, and the Layout Concepts Cobalt S looks like an inspired interpretation of these outdated mechanical switches.

Part of the draw for me is that although I have read and understand the fundamentals of LCC -- which is what I had intended to use to control turnouts -- and I think it to be a simple and elegant protocol.

But after a 25 year career in software development -- I am a bit of a Luddite.

I thought I might get involved in the open software sphere when I retired -- but I have not written a line of code scene I retired. :-)

I want to keep a computer as far away from my layout as possible -- I heard JMRI and I feel a gagging sensation.

Just to be clear -- I understand that many model railroaders really love playing the JMRI and experimenting with what they can automate with JMRI -- and I fully respect their joy.

But I spent 25 years getting recalcitrant silicon boxes to do what I want them do to -- in C/C++, Perl, Python, and maybe some Java. All of the real work was in C/C++, the other languages were mostly just part of arcane testing harnesses.

Thill of "look what I can do with my computer" is long gone. :-)

I liked that while it's useful to have a computing device of some kind to configure LCC nodes, once they have been configured, they run as a tree peer-to-peer network of nodes -- no computer needed.

But better than that is purely mechanical control!

At least on the O&O!

I am modeling modern DMU Transit on my (HO) T-TRAK layout, and I am looking for fencing like that in this picture.

It happens that my first train is also an HO NCTD Sprinter. :-)

When I look at most HO scale fencing, it looks way out of scale -- I think due to limitations in casting, etc.

I don't know why my eye is so sensitive to this, but when see metal pickets that are ¾" wide in 1:1 and are 3-4" wide in scale, it really looks wrong to me.

Does anyone know of a good source for HO scale fencing that looks somewhat proportional?

[BTW, the photo comes from this DMU Transit Systems page.]

I don't know if this will work in N scale but in HO scale, the corner modules are 28" x 28" but the straight modules are generally only 24" deep.

That leaves an extra 4", so I used a 1¼" Forstner but to drill a hole to route the corner module feeds. I feel that that it looks a little better than just snaking the feeds under the module.

Incidentally, you can see the "reverse" wiring that I need need because I have crossover modules. Without crossover modules, the yellow track connections are yellow to white and black to blue. With or without crossover modules, the red track is red to white and black to blue.

To consistent with the O&O standard, I have a DCC snuffer at the end of my power bus -- even though the bus is all of 10'. 😄

I finally "finalized" the power wiring on my HO scale T-TRAK oval w/crossovers -- got the module feeds all heat shrunk (?) correctly, PowerPole connectors all correctly seating in the housings correctly, etc.

The red track module feeds have red heat shrink tubing, the yellow track module feeds have yellow heat shrink tubing. The power buses and pigtails all have black heat shrink tubing.

I also found that I have quite a talent for finding a PowerPole "false click" -- where the connector feels like it's seated properly but it's not. Then when you connect them, the connector backs out of the housing and makes a poor connection.

Since all of my modules are wired, I connected all of the wiring without connecting the track and used a track tester to verify that all of the wiring was correct. That is how I discover my false clicking skill.

Finally tonight, I am running trains again.

The layout is HO, the oval is 56" x 95". I am working on two more singles that will bring it to 56" x 114".

The folding tables are 60" x 126", so if I add more modules, I will need to build a bigger garage. 😄 .

I need a device for controlling some model railroad turnouts that will take 15 vac as input and generate DC output, with three terminals: +vdc, -vdc, and common ground.

The power supply will be used to power Kato solenoid turnouts which require a short pulse, and 21 vdc is with specs.

I asked Gemini, and it generated this schematic. I know nothing about electronics, so I can't tell if it this is an AI hallucination, or if it will work?

Should one of the diodes be facing the other direction? Or is that what the little half arrow under the bottom diode means?

I thought would add a new flare for tips and tricks -- things that I wish I was figured out earlier.

That's mostly because I am unlikely to build another module for at least another year or so -- I have a lot of ballasting and scenery work in front of me.

I am confident that in a year, I will have forgotten everything I have learned. :-)

My hope is that if I save them in this subreddit, I will be able to search and find them when need them.

In this case, when I am assembling a laser cut kit, I have had the thread insert go in at an angle that that means that the top of the adjustable leg is no longer aligned with the hole in the top of the module.

The trick here is to thread the leg in backwards -- from the top of the thread insert -- and then stick the leg through the hole in the top of the module -- as in the picture.

Now when I screw in the threaded insert, the leg will be aligned with the hole in the module top.