Monday, 24 April 2017

Well connected

I've made a start on the wiring for Smestow.  I know it might sound a bit backwards to some that I have started the wiring before laying any track on the scenic sections of the layout but, the idea is to do as much of the basic wiring as possible so as each section of track is laid it can be tested and checked as work progresses.

I'm still sticking with conventional DC control for locomotives and other traction but I'm also developing my own local bus system for control of servo point and signal motors. This should reduce the number of wires going back and forwards to the control panel.

MERG have a range of similar modules in the members kit locker but I enjoy experimenting with electronics and I'm in the process of designing and building my own local bus system using cheap and easy to obtain parts from several sellers on Ebay.

 This was the state of play with some of the wiring this morning.

Note that I use good old fashioned solder tag strips rather than the screw connector blocks.
Just my personal preference as I always think that a good solid soldered joint is far more reliable than screw terminals.

I find that screw terminals have a tendency to shake loose over a period of time and throw up all sorts of faults.

Having said that, some of my modules will have screw terminals just to make a quick disconnect and removal of modules for any modifications and alterations that I might want to make.

The picture shows the underside of the end base board and the solder tag strips can be seen, the tags are wired to a 25way D connector that will connect the control panel to the layout.

The circuit board in the centre is just a 15V DC distribution board and feeds power to other modules individually.
Below that is the 5 V DC power supply to provide power to the servo motors.
I'm using a bit of a mixture of servo drivers for the points and signals. I have some Heathcote electronics modules salvaged from one of my old layouts and some MERG servo drivers that I haven't used before but at the price for the kits are as cheap as chips.
The only drawback with the Heathcote modules and cheap Ebay servo motors is that the servos tend to kick quite violently on power up. To overcome this I have incorporated a timer circuit in the motor supply line.

On start up power is applied to the control modules immediately, but there is a two second delay before the motor power is applied. this gives the control modules time to settle down and stops the servos from jittering on power up. .
As I said earlier some of the control modules are still in the development stage but I will update this page as and when things develop.

Sunday, 16 April 2017

On the fiddle again!

The fiddle yard for my new layout "Smestow" is just about finished.

I decided to build a 360 degree rotating turntable type fiddle yard but with some design changes learned from mistakes and errors made when I built the two similar fiddle yards for my old layout "Steam on the Cambrian"
 Why a 360 deg turntable type?
I had to choose between a parallel traverser, cassettes, a fan of sidings or the turntable type.
Apart from the turntable type all the others require manual handling of stock.
A fan of sidings takes up too much room,
I've used cassettes in the past and found them to be a pain in the backside, especially if they are over 600mm long, With the turntable type manual handling of stock is kept to a minimum.

The base frame is conventional 2x1 (Actually 44 x 18) timber with the centre stretcher being 34mm thick. The deck is made from 12mm plywood and the centre pin turns on small roller bearings.
I did try a "Lazy Susan" type bearing but there was too much rocking and play so that idea was abandoned.

The deck is 3ft long and 1ft wide and accommodates 5 tracks. Alignment is by a home made door bolt made from brass tubes. I tried a conventional small door bolt but there is far too much play in it to be reliable. Rather than rely on mechanical bolts for electrical continuity I hard wired a jumper cable with jack plugs between the fixed and moving sections. This then feeds into switches to control the electrical supply to each track as required.                                                                                         
There is a swing up barrier at each end to prevent any locos or stock from running off the turntable as it is rotated.  As the tracks are soldered to copper clad boards at each end and can not move 
I cut expansion joints in all the rails along the table centre line.  Short jumper wires are soldered across these joints to allow electrical continuity.                                                                                       I also soldered check rails at the ends of each track and on the fixed track to help alignment and hopefully prevent any tendency for stock to derail. Track used is just normal Peco 00/H0 code 75 which is OK for this job. On the scenic sections I shall be using Peco code 75 turnouts and a mixture of both the new Peco code 75 bullhead track and some C&L track that I have left over from a previous project.                                                                                                                                         Well that's progress up to date and is how things stand at the moment. I'll post updates as and when it happens                                                                                                                                                        
Cheers for now    Frank