Saturday, June 25, 2011

Electric spaghetti

Parva Wiring

There seems an awful lot of wire under this tiny layout !

In an effort to keep things simple, I've done my best to colour code everything. Red and black wires are for track power. Blue and white change the points and yellow is the common return that completes the point control circuit. These last colours have been the standard scheme on my model railways for a few years - partly because it makes things easier to remember but mostly thanks to three drums of cable in those colours I was given many years ago...

At first glance, this looks complicated but it's really just repeats of the same circuit. Each point has three wires - a common and one for each directions. Track feeds are duplicated so the power goes in at the toe end of each point. There also a bit of wire on the point motors to switch the frog polarity - something you don't need for RTR points.

The electronic dubrey at the bottom of the board with two "tubes" is a capacitor discharge unit. It's job is to take 16V AC and store it up. When the button is pressed to throw the point, the CDU supplies a big jolt of electricity which makes the solenoid action more positive.

Finally the wires are stuck to the board bottom with glued strips of paper. I know you can get proper clips but the board surface is too thin for nails and screws. Self-adhesive clips always fall off the wood after a few months. Gluey paper has lasted for 25 years on one layout so I think I'll stick with it.

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