DMX Ardweeny Node




Introduction: DMX Ardweeny Node

About: I'm a professional cinematographer with a geeky electronics fascination. I've loved all things blinky since I was a wee tot. From the lights of Karamursel, Turkey as a toddler, to my 100-in-1 Electronics Exper…

Hi Instructable..ers,

I've settled on the lighting industry standard of DMX as my overall control protocol as I explore the world of blinky lights. This universal control method is electrically robust, radio transmissible, and flexible enough for my needs (not to mention the needs of major concert, theatrical, and entertainment venues.) There are a variety of DMX sequence controllers from free to thousands of dollars.

To that end, I designed a single-board DMX receiver that serves a Solarbotics Ardweeny daughter-board. It features;

o an on-board 5V power regulator - 1AMP capacity
o 5V header for powering other devices (or it can serve to power this board from another regulated supply.)
o opto-isolation to protect the Ardweeny from spikes on the DMX lines
o Arduino analog and digital pin-outs for controlling other gear with your Arduino sketches
o RJ45 jacks for DMX connections (using low-cost Ethernet cables popular amongst lighting hobbyists)
o no DMX termination on board (be sure to place a 120ohm resistor across the last jack in a series)
o on-board PROGRAM/RUN slide switch that disconnects the DMX line from the Ardweeny so you can program it via the ICSP header.

Just rewrite the Arduino code to control any device with DMX.

design references: - The excellent kits designed by Robert Jordon and other amazing contributors. I currently own the EtherDongle, Rx/Tx transmitter/receivers, and Lynx Express 16-channel dimming system. (of course)

Matthias Hertel, - who has written the most effective DMX sender/receiver library I've found to-date.

major design decisions included;

o feed DMX to the flexible Arduino platform
o build cost less than any similar offering (this comes in at $33 with my volume purchased parts from ebay/China)
o through-hole design for easy assembly
o RJ45 jacks rather than XLR to take advantage of lower-cost Ethernet cables
o can provide power on the board for low-amperage projects or can be powered by larger supplies
o DMX isolation to protect the Ardweeny from transients (I also have a version with power isolation)
o Ardweeny can be easily replaced if damaged

very basic design steps:

o settled on design parameters (above)
o designed schematic and PCB in SparkfunPCB - a free PCB design tool
o checked fit of all components by printing the PCB to paper and punching parts through the printout
o considered burning the PCB at home but backed off due to the tight double-sided tolerances of some of the small vias
o submitted the Gerber design output files to (a service of SparkFun Electronics)
o received the PCB boards and populated one

Here's a very simple Arduino sketch that controls the 8-channel relay board in the photo. (You'll need to install the DMXSerial library written by Matthias Hertel at


// DMX_Relay_8ch_v01 - September 15, 2012
// receives DMX data and operates an 8-channnel relay board via digital outs
// DMX routines Copyright (c) 2011 by Matthias Hertel,


//this device's DMX start address
// number of DMX channels to reserve for this device

//output pin setup (The number of indices in the array should match DMX_NUM_CHANNELS.)

byte relay_pin[DMX_NUM_CHANNELS] = {2,3,4,5,6,7,8,9};

void setup()
//initialize DMX receiver

//initialize pin outputs
for (int p=0; p

pinMode(relay_pin[p], OUTPUT);
digitalWrite(relay_pin[p], LOW);

void loop()
for (int p=0; p

if ( < 128)
digitalWrite(relay_pin[p], LOW);
digitalWrite(relay_pin[p], HIGH);


If you want to try this project:

I have some spare PCB's or you can order one at

I might sell a complete PCB/parts kit. Ask me.

Bill of Materials
1x PCB via
1x Solarbotics part # KARDW
1x GN137 Opto Coupler DIP-8
1x MAX485EPA RS485 DIP-8
1x L7805ABV Voltage Regulator 5V 1A TO220
1x 1Kohm Resistor
2x 470ohm Resistor
1x 0.1uF ceramic capacitor
1x 0.33uF ceramic capacitor
1x IN4001 diode
1x 5mm red LED
1x Header 2-pin 0.1 spacing
1x Header 6-pin 0.1 spacing
1x Header 13-pin 0.1 spacing
1x 5.5mm barrel jack - Spark Fun Electronics SKU : PRT-00119
2x RJ45 PCB jack, right-angle, no shield
1x SPDT slide switch or 2-pos header with jumper


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    Question 1 year ago

    I am trying to use your simple code to control a 4ch rely board. But I am not sure about the wiring. I have connected it the following way, but it doesn't work:
    RO > Pin 0 on Arduino
    RE > GND
    DE > GND
    DI > Not used (maybe pin 1 on Arduino?)



    Answer 1 year ago

    Hi Lachlan,

    First, I was reviewing this instructable for clarity and discovered a soft bug in the code. Nothing that should affect you, however. To correct it, I replaced the use of hard-coded "8" with the fixed variable, "DMX_NUM_CHANNELS" where needed. Set that variable at the top to the number of relays in your setup, enter the Arduino pin numbers into the relay_pin[] array, and you should be good to go.


    If you read the updated code carefully, you will see I created a layer of abstraction by defining my desired Arduino pin numbers in relay_pin[].

    The reason for this abstraction is to make the code easy to change, later. You only have to change DMX_NUM_CHANNELS and relay_pin[] and the code runs for any number of relays you choose without having to scrub through the entire code, changing "8" to "4." While that seems unnecessary for such a small program, it's a good habit to get into when your code swells to hundreds of lines.

    I, first, define the number of pins to be used with

    Then, I define the pin numbers with
    byte relay_pin[DMX_NUM_CHANNEL] = {2,3,4,5,6,7,8,9}.

    These are the pins to which an 8-channel relay board would be attached.

    Finally, as the FOR loop inside void() counts from 0 to DMX_NUM_CHANNELS, it uses each index value inside relay_pin[] to determine the Arduino pin number to change. In my example, then, the code processes pin 2, then 3, then 4, up through 9.

    In your case,
    o Change DMX_NUM_CHANNELS to 4.
    o Change relay_pin[] to read "relay_pin[DMX_NUM_CHANNEL] = {2,3,4,5};
    o Connect your relay board with ;
    - relay 1 connected to Arduino pin 2
    - relay 2 to pin 3
    - relay 3 to pin 4
    - relay 4 to pin 5.
    o And, the relay's power and ground pins would go straight to the +5 and ground rails.

    Hope that all helps.



    4 years ago

    how does this work, in practice? How does your DMX controller actually control the relays? The code would make it look like all eight are activated, once the address is over 128?
    How could you set an address for each relay?


    Reply 4 years ago

    Hi Joe,

    The if statement "if ( < 128)" is querying the DMX address for its VALUE - 0-255. If that value is below 128, set the pin to LOW, if 128 or higher, set the pin to HIGH.

    So, if the DMX starting address is 1 (as it is in the sketch) the FOR loop runs from 0-7, checking the values of DMX addresses 1-8.

    This is a very simple sketch. You could, of course, write a more complex one that checks any combination of DMX addresses and operates attached peripherals through the Arduino pins - dimming, blinking, activating, etc.