Rewiring the rear boards

One week into 2017 and three of the tasks on the resolution list are close to being completed!

Work has begun to repair, rewire and modify the wiring on the rear three sections, starting with relocating the edge connectors so that patch leads can be used. Although these have worked really well, it's difficult to fault-find when the boards are clamped together, on some occasions the boards have had to be split just to disconnect them. This will make diagnosis much easier.

Next job was to sort out the points that had stopped working. I suspected that the problem was with the control boards that I built some time ago. Although they've worked pretty well, the PCB boards were too small when acquired, so the capacitors had to sit above the relays. In a loft scenario this wouldn't be a problem but mounted under the rear boards (which were then stacked upside down on the front boards) they were prone to being knocked and several of the solder joints have been damaged as a result. So time to replace these...

For something mass-produced, smaller and hopefully more reliable... 

I haven't been able to find double pole relay PCBs, so two relays will be needed for each pair of points - one relay to control the solenoid, the other for track isolation.

Each relay has its own trigger, we simply have to link the four inputs to the eight relays.

More capacitors required, 4700uf at 25 volts should do the trick...

 Here, the live feeds have been wired & linked (red) while the relays that need to be linked are starting to be wired...

1-5, 2-6, 3-7 & 4-8...

The capacitors are designed to be mounted on a PCB, so for this application I've used heat shrink to protect them...

Now the common return connection for the points solenoids is added...

The points solenoid control is now done...

Now the links are added for the four pairs of points in this section (one from the main loop which feeds three sidings) and then the job is finished, ready for installation (just a few more to make!) 

From top to bottom - The new control for the three upper loop points on the new rear upper section (not yet wired) below that is a further three points control module, a home-built one which is made to a much better standard using a larger PCB, this operates the three sidings that are accessed from the turntable sidings at the front. Below that there is a central wiring connector block where two of the new controllers have already been screwed into position, with one of the old controllers still wired in and slowly being removed...

The new controls are much shallower and with the new trailer racking they should never get knocked.

Testing with a transformer. The other main advantage of these PCBs is that they contain a power indicator LED and individual LEDs for each relay - no more scrabbling around with a multi meter & torch when a pair of points fails, now all I have to do is look to see if I have a green power light and two red relay lights for each pair of points. Simples!

The new, rear upper sections now contain three pairs of points at each end, so two more controllers were needed. Here the points are wired to a 9 pin RS232 connector.

And the other end of the connector is wired to the module. 

The same process now needs to be applied to the board at the other end. The centre board has already had its wiring modified for the additional upper loop points and the module for the other end has also been installed. Hopefully if I've wired them right this time, the siding isolated sections have also been re-instated.

Sadly I can't test this little lot without assembling all three boards, so it'll have to wait until the next exhibition.

The new relay boards may look over-engineered but in reality, for what these have cost me, I couldn't have built them myself for the price I paid for them!