A Maintenance Record
Mallard, Scotsman, etc
Fowler 2F and Ivatt 2MT
The 2-10-0 Workhorses
Solid, Robust, Reliable
Not Minitrix & Non Uk
On Minitrix Models
Classic UK Minitrix Models - DCC Overview
for any DC conversion
In coventional wiring, the voltage or current applied to the loco is controlled before the wiring reaches the track. In the loco, the contact with the track is connected directly to the motor. In the early minitrix locos that this site focuses on (ie the period up until 1982 when Trix stopped supplying British Outline models), the chassis of the model is connected directly to the negative power supply provided by the left hand track.
DCC does things
differently. Instead of a 12 volt supply, we have 16 volt.
In the loco, we place a small chip. This has the job of picking up the power supply and the signals from the track, decoding the signals and doing something as a result of the information that it has decoded. This includes:
Of course, it has to do a lot of other stuff, and it does it all over and over again, many times per second.
From all of the above, two things are important for the DCC controlled layout.
There may still be documents lurking around which say that you cannot put a DCC chip into a model that uses the chassis as an earth. I read this a number of times when I first started with DCC in my Minitrix models, but it is rubbish. You can, but you have to be aware that the chassis is being used for the negative power supply, and isolate the motor from it.
Basically, everything goes through the chip. The power from the track goes into it. The controlled power to the motor, lights and any other gizmos that you have, come from the chip.
This DCC chip or wiring socket has 6 wires
Blue - if a 7th wire is available, is the common return lead for the directional lighting on chips with 7 wires.
In a chip with only 6 pins, there is no common blue wire for the lights. Instead, the chassis connection is used as the common return. This results in the lights being lit for only one half of the AC cycle, so will appear slightly dimmer. This is fine, since the bulb in the loco is connected to the chassis, and wiring it in any other way would be a pain.
Finally, a word on electrical continuity. Before fitting a chip to any loco, make absolutely sure that it runs perfectly well on a DC track. DCC seems to be much more prone to tiny breaks in the circuit - eg going over points, or slight bumps in the track which may lift the wheels momentarily. In such circumstances the chip loses the signal. From my own observations, if there is an inertia setting so that the loco accelerates gradually, then the effect of the momentary disconnection is that the loco suddenly stops, and then accelerates gradually back to its speed setting. Other chips and controllers may behave differently.
for any DC conversion
Maintaining Classic UK Minitrix Locos