Banbury_in_00 (Posts about digital_control)

A Fourth Control Panel

Tim Pearson — Thu, 30 Jun 2022 12:00:00 GMT

I have stupidly been working on what has become a large piece of software for automatically controlling the signals in the layout - possible because I know which sections are occupied and can track point state changes. Automatic signalling is not trivial as the code needs to understand the complete connectivity in the layout.

One problem I have is that the dapol semaphore signals seem to 'forget' their polarity from time to time so I have to have an easy method of working around that - so I am building a control panel to have a set of switches which can be used to alter the polarity (and one switch to turn all signals to danger to see if any need altering).

I also want to be able to control the lighting system so have put in some WiFi (UDP) control of the PiZeros that run that - so also have some push buttons for controlling the scenic lighting

Station Lighting System -PCBs

Tim Pearson — Wed, 07 Apr 2021 12:00:00 GMT

I need to get a lot of lighting onto the station building and platforms - each lamppost that I have made requires two miniature LEDs and the building itself will probably need several score. I'd also like for each scenic component to be removable e.g. the platforms. Without a mess of wiring.

Ideally I'd also like the LEDs to be programmable so I can e.g. simulate flickering fluorescent tubes and coz I am a geek.

I settled on using Raspberry Pi 2 ZeroW as the controller device - cheap and with programmable outputs. But each output is very low current maximum and would only drive a couple of LEDs.

So I need some driver circuitry that can be controlled from the Pis - I have chosen a ULN2003A Integrated circuit where each Darlington pair can give 0.5A which is enough to power more leds that you will ever need on one output.

Then I would like to power the Pi from the same power supply as the LED power supply so I will use a little step down DC-DC converter that takes 9V and gives 5V (TSR 1-2450). I want to use 9v so each lamppost pair of lamps can be controlled on a single circuit.

So I have designed three relatively simple PCBs

A Controller 'hat' for the PiZero with four 10 way ribbon cable connectors and one 2 way PCB terminal block for power input.
A 10 way break out PCB particularly for use under the platforms so can have a maximum width of around 16mm.
A terminal block and resistor PCB that will connect two LEDs via lever connectors and have a location for the resistor

I have designed these in Eagle (before I switched to the much preferable open source KiCad as Eagle has been destroyed by Autocad).

It is incredibly cheap to have PCBs made these days each one is under a pound for production and shipping.

So I mount the PiZero with the hat under the circuit with a single 9v feed then a 10 way ribbon cable runs to the underside of the platform that then feeds the individual terminal blocks which can connect one or two LEDs each on their own circuit.

My intention then is to have wireless control of the LEDs from a single master Pi or similar.

More Appch Wiring

Tim Pearson — Sun, 05 Jan 2014 12:00:00 GMT

Still cracking on with the Northen Approach board wiring - getting bored with it now.

Whilst in some ways I wish I had bought DCC Concepts cobalt point motors instead of the Tortoise motors I am using (because their smaller size makes for less problems in squeezing them all in) One thing I like about the tortoises is that you can have a harness with an edge connector which you can just pull on or off as you are building.

In the picture you can see the blue edge connectors attached to some of the finished motors.

A chance to make some progress

Tim Pearson — Sat, 28 Dec 2013 12:00:00 GMT

After a stupidly busy couple of months, the Christmas break has allowed a few days of fairly continuous work on the approach board (that I see from this blog I started in June).

I now have all of the points mounted on the northerly station approach board...

The flange screws you can see between the rails holding the trackwork in place are to allow for minor adjustments, the track will eventually be glued into place when the track is ballasted (at least a year away) and at that point the flange screws will be removed.

I want to check that the track runs perfectly before gluing it down.

I just can't work kneeling down for more than a minute or two so I have tried to make the construction of the layout as modular as possible - such that I can either work at my workbench or at least standing up. To that end the boards are all to some degree removable and the electronics are as modular as possible...

This board is the most complex, it requires 14 point motors and the track-work is split into 15 separate occupancy detection sections. This is because the complex station throat point work has so many possibilities that the required continuous track detection is tricky.

Continuous track detection means the computer never has to guess where a train is. It requires two things - (1) all track be occupancy detected (2) no single occupancy sensors are going to have two separate trains on simultaneously under normal operation.

The electronics for this board (like all of the electronics) hangs on hooks from a supporting L-girder in this case it contains 2 CML DAC-20 Digital point controllers and one Digitrax BDL-168 occupancy detector board.

The feeds to the track and points are mounted along the top on pluggable connector blocks, the feeds into the electronics are two cables attached on the right hand side by locakble circular connectors - one carrying the track feed and one the various power supplies required for the electronics.

There are 6 separate track feeds that come from two central Digitrax PM42 boards - these mean that any short circuit is more easily identifiable as it only affects one area of the track. One track feed goes to each of these hanging electronics boards. The whole board is assembled on the workbench and then can be plugged in when in position with no further wiring required, thus saving my knees.

PCB Mounting Boards

Tim Pearson — Sun, 16 Jun 2013 12:00:00 GMT

Working on the next under layout mounting boards for the various electronics PCBs that control the points and occupancy detection (and perhaps signals later)...

Here are the next two (of 5 so far) completed, at least as far as wood and metalwork is concerned...

Panel Testing

Tim Pearson — Thu, 18 Apr 2013 12:00:00 GMT

The panel works (mostly) but there are some gremlins to get out, not all of which I think are my making...

The green LEDs show position of points, the blue LEDs show section occupancy.

There are also red and yellow leds to show if computer or human has control of a track - but these are not lit in this test.

Control Panel

Tim Pearson — Sun, 20 Jan 2013 12:00:00 GMT

The layout is going to need three control panels. I have decided to make a start on one (the one for the fiddleyard and junction) before I progress with the next bout of woodwork.

The electronics are the easy part (remind me I said that later) I am going to use two CML DTM30 boards in a single box. The box will have approx 25 point/route setting push to make switches and around 70 LEDs to show occupancy and point / route setting.

My main concern being a messy sort who has little design skill or flair for such things is how to make the panel look acceptable.

I have started by drawing up the panel I want on Excel and the printing that to pdf for an A3 size sheet. Then I have sent the pdf off to a printer to print onto some tough waterproof paper (£2.50 per sheet). Here is a picture of the diagram...

I had considered sandwiching that between an aluminium base and a perspex top but I found that the perspex was too tricky to drill without it cracking. I could perhaps do ten successfully but here I will need to do a lot more than that. So I have just gone for waterproof paper on a 1.5mm aluminium base -

Here is how the paper arrives through the post...

And here it is after I have cut it to size and drilled some holes in it. I found that using a wood drill the 7mm holes for the switches came out neatly - but the smaller ones for the 3mm leds tended not to cut so neatly so I will drill those after I have stuck the paper to the aluminium.

Drilling the switch holes in paper and metal separately means I have to try and be fairly precise I expect this will need some adjustment as even with the pillar drill I can see I am slightly out in places. Anyone got a handy CNC machine?

North End Of Fiddle Yard Electrics

Tim Pearson — Sun, 09 Dec 2012 12:00:00 GMT

I have now just about completed the under circuit wiring for the North End of the Fiddle Yard (actually it is only North by orientation of the room - on the modelled location it would be the South end) - Becuase I am so incapable of working upside down these days I made the board with track breaks at both ends so that it could be lifted up later - although the overpass track will need to be removed.

The electrics have taken a long time, as there are something like 35 different track feeds to the yard (in order to get occupancy information) as well as 14 points that each need polarity switching for electrofrog and point motors connecting up.

You don't actually have to do polarity switching as the points do it internally these days but the mechanism is not the most robust so I use prefer to do motor contolled polarity switching.

Because some occupancy sections cross the board break I have to do some cross wiring to the South side and vice versa which adds some complexity. As ever I am fighting to keep it neat.

Still at least it all seems to work.

Two Wire DCC HaHa

Tim Pearson — Wed, 22 Aug 2012 12:00:00 GMT

For the last three weeks I have been fitting the point motors and wiring up the South end of the fiddle yard - even after taking great care to try and keep the wiring neat it still looks a bit of a birds nest.....

Fiddle Yard Construction

Tim Pearson — Fri, 03 Aug 2012 12:00:00 GMT

I have spent much of the last few months making slow but steady progress - I have built four of the control boards I need - including the power distribution board which contains 2 x PM42 power distribution thingys from Digitrax. This allows the network to be separated into a number of separate power feeds - on a large layout like this it also helps short circuit detection in that you can immediately see which area of the network you have a short on. Finally it does the job of inverting the polarity for the reversing loop. The power distribution board also distributes three other AC and DC supplies for powering various things - You can see it propped up on top of the basebaord on the left of this picture...

It does seem though that I have enough power feeds to supply a good section of the london underground!

I have also installed under the reversing loop slope section an infra-red detector to automatically change the reversing loop point whenever a train is approaching it. This works well apart from the fact that it doesn't always initialise to the correct orientation - I have not investigated cause or solutions to that yet.

Hopefully I can now lay the track for the fiddle yard quickly as I have built the control boards to supply all of the points - 14 or so and all of the detection sections 28 or so.

One of the reasons for my lack of updates on this blog is the update to Mac OS X 7 - my own blog writing software (written in objective-c) used older Operating Sytem calls no longer supported in OSX 7.x so I had to open up the software and fix it - a trivial job in itself but downloading the latest development environment on my slow link and educating my slow brain in the changes to the OS API was a big obstacle! .. thumbnail:: /images1014/FiddleYardBaseboards.jpg

Banbury_in_00 (Posts about digital_control)

A Fourth Control Panel

Station Lighting System -PCBs

More Appch Wiring

A chance to make some progress

PCB Mounting Boards

﻿Panel Testing

﻿Control Panel

﻿North End Of Fiddle Yard Electrics

﻿Two Wire DCC HaHa

﻿Fiddle Yard Construction

Panel Testing

Control Panel

North End Of Fiddle Yard Electrics

Two Wire DCC HaHa

Fiddle Yard Construction