Modular DCC micro control unit - Main power module

This main power module, on its own, functions as the minimal DCC micro control unit. Combined with a computer and JMRI software, it is capable of controlling all decoders connected to the rails of the rail network (locomotives, points, signalling, animations, etc.).

The module has various side connectors, enabling it to add new functionalities by connecting different electronic assemblies (Bluetooth joystick, current consumption monitoring, etc.). The BLE joystick module makes the module completely autonomous, eliminating the need for a computer during operation.


The new features in this version are as follows:

  • added locomotive presence detection on the programming section;
  • addition of a 5V regulator to eliminate dependence on USB power supply (in anticipation of WIFI network control);
  • analog current measurement connector added;
  • addition of a digital current measurement connector;
  • addition of a wireless control connector (BLE or WIFI);
  • adjustment of LED protection resistors according to color, to harmonize the visual consistency of the control unit.

Maturité : 80%

Project status


Version 1.0

The PCBs are mounted and the first tests have begun. No malfunctions have been detected. Several minor modifications are already planned for the next version:

  • enlarge the pads of components R10, R12, R13, D12;
  • modify the Q2 footprint (identical to Q1);
  • increase SW2 hole size so that the switch is firmly attached to the PCB;
  • offset U4, which is too close to the spacer;
  • add the motor detection indicator and switch on the top side.

Version 0.5

The assembly was carried out on a breadboard to check the general operation of the project. The microcontroller software is identical to the minimal DCC microcontroller. It has already been validated.

Version 1.0

Version 0.5

Electronic schematic (version 1.0)

The heart of this assembly is an Arduino Nano v3 board. Its microcontroller is loaded with the DCC++ program adapted to the characteristics of this circuit.

Commands are sent to the microcontroller either via the serial link (USB) from a computer running the free JMRI software, or via the external DCC control connector (J4).

The DCC signal generated by the ATmega328 microcontroller passes through a power circuit (L298N) before being sent to the rails to control locomotive decoders and various DCC accessories.

Hardware requirements (version 1.0)

Description Quantity Reference Search url
Tantalum polarized capacitor 1µF 1 C1
Capacitor 100nF 4 C2, C4, C5, C6
Polarized electrolytic capacitor 470µF 1 C3
Polarized electrolytic capacitor 10µF 1 C7
Diode 1N4001 8 D1, D2, D3, D4, D5, D6, D7, D8
Pin socket (3x) + pin header (3x) + 3mm two-color LED (green and red), common cathode 1 D9
Pin socket (2x) + pin header (2x) + 3mm yellow LED (programming) 1 D10
Pin socket (2x) + pin header (2x) + 3mm blue LED (operation) 1 D11
3mm red LED (presence detection) 1 D12
PCB-mounted 15V power supply jack (5.5 x 2.5mm or 5.5 x 2.1mm depending on transformer plug) 1 J1
Rail power supply socket (3-pin, 3.8mm pitch, right-angle for PCB mounting) 1 J2
Magnetic connection socket for measuring current consumption (3 pins, 2.8 mm pitch, right-angle for PCB mounting) 1 J3
Magnetic connection socket for external controls (4-pin, 2.8mm pitch, right-angle for PCB mounting) 1 J4
Magnetic ammeter connection socket (2 pins, 2.8mm pitch, right-angle for PCB mounting) 1 J5
Pin header (2x) jumper: short-circuit to avoid using the ammeter 1 J6
Transistor NPN PN2222A 1 Q1
PNP transistor 2N2907 1 Q2
Resistance 0,1 Ohm (2 W) 1 R1
Resistance 1K (1/4 W) 4 R2, R6, R7, R12
Resistance 10K (1/4 W) 3 R3, R8, R13
Resistance 2K (1/4 W) 3 R4, R9, R10
Resistance 4,7K (1/4 W) 1 R5
Resistance 220 Ohm (1/4 W) 1 R11
Pin header (2x) for emergency stop button (diameter 16 mm) 1 SW1
Pin socket (12x) + pin header (12x) of 4RT switch for mode selection (operation / programming). 2 SW2
Pin header (2x) for restart button 1 SW3
Pin header (2x) for presence detection LED 1 SW4
Arduino Nano v3 + pin socket (15x2) 1 U1
Double H-bridge L298N 1 U2
TO-220 aluminium heat sink 25 x 23 x 16mm with two fixing pins 1 Fixation U2
Dual LM358 OP amp + 8-pin DIP support 1 U3
5V controller 1 U4
Optocoupler 4N35 + 6-pin DIP support 1 U5

How it works

In progress...

Printed circuit boards (version 1.0)

In progress...

Copper face up

Copper underside

Component layout diagram

Component installation

In progress...

Assembly operations

In progress...

Software loaded in the microcontroller

In progress...

Preparing for the first start-up of the micro central unit

In progress...

Power on

In progress...

Network driver software: JMRI

In progress...

A 3D-printed case for a perfect finish...

In progress...

To find out more...


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