wiring DCC points

I am asked so often how to wire up DCC points that I am now including this piece. Unlike DC wiring, the track remains live throughout at all times. The downside is that it is only too easy to drive a train into a point that is set against it. This can be prevented by extending the length of the isolated sections of the frog.

This is the simplicity of DCC as you no longer have to worry about isolating sidings in order to stop the wrong locos working as you choose the loco you wish to operate by selecting its address. If the layout is already wired for DC, it will almost certainly work for DCC as well, by the way. The only problem will be that you won't be able to run another loco on one of the isolated track sections.

So let us first look at the basic wiring requirement.

The only thing we have to do is to change the polarity of the frog and blades when the running direction is changed. This means that the frog must have insulated joints to prevent a short circuit. Click on the switch below to animate.

DC turnout - click on switch to operate

Despite many articles that describe 'DCC Friendly' points, I do not bother to install them. If you are using Peco 'Crazy track', it would be very difficult to convert to 'DCC friendly' anyway.

Just to explain what DCC friendly points are. Some people are concerned that when running DCC which has a slightly higher voltage (15VAC), a wheel might short circuit between the blade and stock rail, so they add an additional rail break so the the blades are always the same polarity as the adjacent stock rail. Indeed, learned article abound on the web about 'friendly' points. Again, click on the switch to see operation. I find that it is quite unnecessary to go to all this trouble and I think one is more likely to damage the very delicate small points. A few locos or bogies may indeed touch the wrong polarity blade and cause a short circuit. This is quite rare and the first thing to do is to check the back to back measurements again. The worst offenders are Riverossi power bogies which have flanges deep enough to cut into the Earth's crust. The only solution is to give two coats of varnish to the backs of the wheels (I use Ronseal). Once hardened, the problem has gone.

DCC 'friendly turnout' - click on switch to operate

So lets look at the installation using Peco point solenoids and polarity switch. Firstly, I solder a 'dropper' (a thin length of wire) soldered on the underside of the frog. Once the exact position of the point has been established, drill a hole in the baseboard to allow the dropper to pass to the underside and drill a slot to give adequate clearance for the actuating rod which passes through the hole in the tiebar. The point is then fitted and fastened down (I just epoxy them onto the baseboard). The fishplates are soldered to the adjacent rails but do not forget to use insulating fishplates on both sides of the frog.

I then temporarily wire up the solenoid including a switch and then epoxy the motor to the underside of the baseboard. I make sure that the blade are held midway between the stock rails and that the actuating rod is at the centre of the slot. As the glue begins to go off, I operate the point and adjust if necessary to ensure that there is an equal throw and that the blades go fully over.

Once the glue has gone off, I add the polarity switch which I also glue on.
 

• Make sure that the motor is placed at the centre of the throw. If it is not, you will see the actuating rod bounce back toward the centre. If this happens, the polarity switch will not operate.

• If you do have to remove a glued solenoid motor, a couple of light taps with a chisel will release it.

You are then ready for final wiring. The Peco solenoid motor is operated through a Capacitor Discharge Unit (CDU). This gives a good belt of electricity which powers the solenoid. CDUs are powered from a 15V AC transformer. You must use a momentary contact switch as holding power onto the solenoids will burn them out. Click on switch to operate the image below.

 

The Peco turnout maintains blade position by a small spring hidden near the tie bar. These can fail and the system will no longer properly hold the blades in place. If this happens, you can replace the Peco motor with a latching Seep motor which is available from Gaugemaster. The wiring is the same.
 

In 20:20 hindsight, I made a big error in using Peco point motors on the fiddle yard. We use DAC 10s (CML) and DS44s (Digitrax) to operate the point motors. There is the facility to set these units for operating solenoid motors as they have built in CDUs, however the signal was just not strong enough to operate the points. We therefore had to use the signal to operate relays connected to a large CDU in the fiddle yard.

This worked but required a four second delay in operation between each point actuation when routes were being set by the Railroad & Co software. This much delayed the time when trains were not operating on the line.

In the end, we have also been forced to add individual CDUs to every point. This has meant that three 24V AC power units are needed to operate them but at last, the routes can be set in 'rapid fire'. Altogether a big mistake and we should have used Tortoise motors to avoid the problem in the first place.