DCC Accessory Decoder – 24 Channels

Having a lot of animation my layout, I came up with a way to control many different circuits using the JMRI software, a Digitrax SE8C signal decoder, a 16 channel relay board, and a simple breadboard circuit. The result is a 16 channel “Accessory Decoder” using only one board. You also have the 8 outputs designed or turnout totaling 24 channels.

The heart of the project is the Digitrax SE8C signal decoder board. Already supported by the JMRI software, it is designed to drive LEDs. You may think this board simply turns current on and off to LEDs, but it actually has a complex output circuit that has bipolar pulsed output. If you take a video of your LED track single you can capture the LED flashing, but to the human eye it looks like it’s constantly on. Hooking up SE8C to a relay will only result it “Buzzing”. The simple breadboard circuit converts the pulse output to a steady DC current that can drive the relay board.

Note: I contacted Digitrax on doing this, and logically their response was this board was not designed to be used in this fashion. The Pulse-To-DC breadboard circuit puts less load on the SE8C than a LED and is harmless to the SE8C.

The relay board I used is designed for the Arduinos and is optical isolated, each relay can switch a different voltage, and is under $50. This results in a low cost, high channel count “DCC Accessory Decoder.