DIY DCC Accessory decoder.

Based on schematics and firmware from Dave van der Locht, OpenDCC en Paco’s website, I created a simple low-cost DCC Accessory decoder.

The decoder uses a microcontroller that can be loaded with the required firmware for the job. This include signaldecoders (including, German, Dutch and Belgium signals), light decoders and trackswitch decoders.

I created special ‘NS Decoder’ firmware that can control Dutch signals, relays, lights and trackswitches without the need of changing firmware.

However, it is recommended to use the ‘NS Signal’ firmware to control Dutch signals. This firmware contains extra code to dim the signals for night operations with one command for all signals. it also includes a permissive signal (green to red via yellow and v.v.)!

The manual and all related files can be downloaded here.

The decoder uses power from the DCC signal. If you want to use an external power supply to control the output, do not connect the jumper to select the power supply. V+ on the outputĀ  is then not connected. You can connect a stabilized power supply to V+ and GND. The DCC signal will then only power the microcontroller and program LED.

The board is created so that, apart from the DCC voltage, also 12V and 5V power supply to the output is present. However, when this is not required, the 12V voltage regulator and it’s associated capacitors can be removed and replaced with a small wire bridge. The input capacitor of 100uF can be made larger (or smaller) when required.

I ordered my PCB’s in China via They are cheap, reliable and provide good quality. Normally you’ll get some more PCB’s then ordered. The PCB zip file can be used to order the PCB’s there. Otherwise you can use the eagle files to create your own Gerber files.