Connecting the Board to your Layout
Each duinoNode requires three power connections:
- V++, device power from 3.3 – 30 volts
- Vcc, +5v logic
- GND, shared ground for both device and logic
V++ & Vcc can be tied to a single +5v feed from a power supply of suitable capacity. Multiple power supplies are supported but not required.
The single most important requirement is that all grounds MUST be tied together. Specifically this means that the microcontroller ground MUST be tied to both logic and device ground.
This usually isn’t a problem IF the entire system is powered from one power supply, or powered using multiple power supplies whose grounds are tied together at the source.
However, when powering the microcontroller via USB or an independent, untied power supply (such as a wall wart), you MUST run a wire from microcontroller GND to GND of all other power supplies in use.
Grounding problems manifest as unpredictable, uncontrollable switching on the boards.
LOGIC IN: Each duinoNode requires three logic connections at J2: CP (clock), LP (latch) & DI (data in).
LOGIC OUT: Each duinoNode offers three logic connections at J3 for the next downstream node in the group: CP (clock), LP (latch) & DO (data out).
All node-to-node data connections can be made with ordinary 3-wire servo extension cables.
The output of duinoNodes is in Common Anode configuration. All switching is on the “sink” or ground side of the circuit via a transistor array. NJ International, among others, wire their model railroad signals, crossings and other devices in common anode configurations. Common anode devices will have a single lead for power and multiple ground leads. Connect anode leads to the V++ terminal, and individual grounds to each port. So long as current limits are not exceeded (500 mA total per board, up to 100% of that can be on any one active port), multiple devices can be connected to a single port.
While logic voltage VCC is always +5v DC, device power can be at a different voltage between 3.3 and 30 volts DC. You can use a single power supply that supports multiple voltages, like a Mean Well RD-125A, or multiple DC power supplies with their grounds tied together.
Special Wiring Scenarios
Common Cathode Devices
The DN08A is compatible with off-the-shelf home automation relay modules, like the one shown below:
For model railroaders, these relay modules are a great way to implement polarity switching for reversing loops, turnout points, stall motor switch machines (like Circuitron Tortoise) and coil-type switch machines (Atlas, Peco, etc.)
These modules work with all +5v Arduinos. Using one or more DN0U1s you can control all of your relays using just the 3 pin connection required for duinoNodes. In fact, you can mix relay control with lighting and other applications on the same duinoNode chain.
You will need to fabricate a cable to connect the relay module to other devices. You can use a female pin header of appropriate size, then attach your cable to the exposed ends. From there, connections are straight forward as shown.