My implementation & DCC "electronics stack"

My DCC implementation is based on my usage.Since I want to:

• MU diesels
• doublehead steam
• use helpers
• have a number of locos on the rails at all times

I measured the current draw on USAT F3 units, and I'm using about 1.7 amps per USAT F3 unit. I need to be able to handle a maximum of 5 or 6 units, so this is a challenge.

I did some further experimentation and found that I lost 3 volts in the booster, i.e. 20 volts DC into the booster yielded 17 to the track.

Next, I experimented with maximum speed on the locos, since you can also drop 2 volts in each decoder. So in the example above, you could yield only about 15 volts to each motor.

The very important thing I learned is that there is not a linear relationship between motor voltage and motor speed. Virtually all the "top speed" in a motor comes from the last few volts applied.

So the difference between 17 and 20 volts to a loco made a BIG difference in the speed.

I found that my USAT locos would only run 62-65 mph at 20 volts on the rails, but would hit close to 90 with 23 on the rails. Absorb this information. This means you need to pay attention to your power system if you need anything near 70 miles per hour from a loco. The USAT locos run fast too, most Aristo locos run more slowly.

Anyway, I needed a big booster, so got the 10 amp NCE one. Originally I bought a big 10 amp transformer from Tony's Train Exchange. I found a perfect box to put it in, from LMB, a #142, 4x6x5" high. But I found the voltage sagged quite a lot under load. Also, since I'm running passenger train also, I needed all the voltage I can get. (A transformer alone is always going to have it's output voltage sag under load).

The voltage to the rails often sagged to 17 volts. No wonder that people say their locos run slow!

The NCE booster has a settable output, but normally it maxes out at about 20.1 volts. I have a calibrated speedometer car, and my USAT F units only went about 67 mph at this track voltage. I checked with NCE since they said the unit could go to 24 volts. I sent it in, they modified it to give me the max voltage. So adding 3 volts, I needed 27 volts in.

So, now I have a regulated 10 amp, 27 volt supply, it's on the bottom of the picture below. The passenger train can now hit 92 scale miles per hour. There are more reasons for having this top speed, it allows you to speed match all your locos (you usually match to the lowest tops speed loco). I bought this supply from TRC Electronics, www.trcelectronics.com it is a Meanwell S-320-27, about $85.

Anyway, back to the power stack, the power supply feeds the booster on top of the "stack" via the red and yellow wires.

The booster combines the input power with the DCC signal from the command station, which is the middle box in the "stack". The output to the track is via the red and white wires. The booster provides power to the command station by the green and yellow wires.

I wired each track feeder to a dual banana plug. They are cheap and can handle lots of amps. You can see the white and red wires feeding the stack of plugs at the bottom right, which are all the track feeds.

The command station, in the middle of the stack, gets the hand controller(s) connected to it, the wireless base station(s), and also has the output for the programming track. You can also see the serial port which connects to the computer in the house that allows computer control and decoder programming (it's the large white plug with the screw slots in the "knobs").

Finally, on top is the 110v on/off switch, and the silver box is the RS-232 extender that allows a remote computer to control the command station.

The enclosure is a 12" x 12" irrigation "catch basin", but inverted. So, normally you would have a drain grate on top, but now the drain grate is the base. Underneath, I have added some finer screen mesh to keep critters out.

The top is the "catch basin" "box". It usually sits in the ground and connects drain pipes together. You glue the plugs in both sides. Put a handle on it and it makes a perfect waterproof cover:

Here's the stack with a DCC Specialties autoreverser added, just use the banana jacks to add it into the circuit, easy, fast.