The Circuit
Schematic Diagram (Fritzing)
Components List
The Circuit begins
Some Pictures
Something about DMX Protocol
The RGB Lamp
Software Code
PCB (printed circuit boards)
NOTES & Improvements

Published March 11, 2021 © GPL3+

DMX RGB Mixer for Lights

Five channels circuit to control Red, Green, Blue, Brightness and Strobo of your LED lamps in an handy box!

IntermediateFull instructions provided5,845

Things used in this project

Hardware components

Arduino Nano R3

Story

The Circuit:

In these days a complete and rich lights control DMX console is available to buy at shops for a few tens of Eur only, but we also know how is interesting and exciting to build one by ourself. Here it is mine, a basic complete circuit to control RGB (red, green and blue) lamps by the way of sliders, in a small handy box. You may also control brightness of all combinations of colours. A push button toggles RGB and STROBO mode, and with the rotary potentiometer you may change the strobo frequency rate. Coloured LEDs are just to remember the single functionality of the sliders, always on. The transparent LED is a multicolour RGB one: it varies his colour following the corresponding RGB sliders and it flashes at 4Hz if the strobo mode is active. Power up the circuit by the way of an USB cable. Connect this circuit to one or more DMX capable RGB lamp using a XLR 3 wires cable (the one used for microphones); put a 120 Ohm terminator to the last lamp.

Schematic Diagram (Fritzing):

Schematic diagram

Components List:

Arduino Nano MCU

C25B TTL/RS485 communication board

10k linear rotary potentiometer

4 x 10k linear slider potentiometers

100nF capacitor

Push button normally open

Red 5mm LED

Green 5mm LED

Blue 5mm LED

RGB 5mm LED

Resistors: 10k, 2 x 680, 120, 2 x 470, 270

25 copper rivets (for PCB pass through holes)

3 pins strip line for XLR connector

DMX (XLR) 3 pin female panel connector

USB-B female PCB connector

4 x huts for the sliders

1 x hut for the potentiomenter

1 x hut for the push button

Plastic black box 129x64x45 mm

USB cable for power

Cover, Ring and Mounting supports (see NOTES below to download 3D models)

Optionals: DMX/XLR 3 wires cable and connectors male+female, 120 Ohm DMX/XLR terminator, one or more RGB lamps with DMX capabilities

The Circuit begins:

The Circuit begins

Some Pictures:

1 / 10 • Top view of the circuit

Something about DMX Protocol

The circuit I am showing here uses 5 DMX channels: ch.1 for brightness, ch.2 for red, ch.3 for green, ch.4 for blue; for each channel their values 0-255 changes brightness or colours according. Channel 5 is used for Strobo mode: in this case the values 0-7 do nothing, the values 8-255 changes the strobo rate. You have to set the lamp with code 001 as first channel number (look at your lamp user manual to set it).

Please read at this link to better understand DMX communication protocol: https://www.theatreartlife.com/staying-still/dmx-demystified/

DMX signal on the Oscilloscope

To test the circuit you may connect the Arduino D3 (3) pin, used as TX, to an oscilloscope and see a signal like the picture above. After that you may do the same connecting the oscilloscope after RS485 board to view two similar signals, one on pin A and the other on pin B, but with different voltage level and A inverted vs. B, as per 485 protocol characteristic. The communication signal is transmitted continuously regardless you are playing on sliders and buttons or not.

The C25B RS485 board already got the 120 Ohm terminator permanently connected as "BEGINNING" of the DMX cable. You have to terminate also the "END" of the cable, or chain of cables, at the last connected lamp if you have more than one, with a dedicated terminating connector with a simple 120 Ohm resistor inside between pins 2 and 3 of the cable. A correct termination is important to be sure the RS485 specifications are respected and everything will work strongly well.

1 / 2 • Single Lamp example

The RGB Lamp:

The RGB DMX lamp I am using with the circuit

Software Code:

#include <DmxSimple.h> The program uses DmxSimple library

#define IS_DEBUG false Change from false to true if you like to see Serial monitor showing you what happen when you are playing with controls

const byte TTL485Pin = 3; This and other lines to declare all input and output Arduino pins used in this project

void setup() This block of code to initialize library and in/out pins

void loop() Main block code: reads button, trimmer and sliders, and according with refreshRate (set to 200m/sec) transmits information about RGB colours and strobo to the lamp/s by the way of RS485 module and XLR cable.

void blinkLed() Used to blink at 4Hz (four times per second) RGB led when strobo mode is active

void readButtons() Reads digitally if the RGB/Strobo button is pressed and sends information to the lamp/s

void readTrimmers() Reads analogically the actual position of the trimmer and the four sliders; it also "maps" the values from 0-1023 to 0-255 (from 10bits to 8bits)

void writeDMX(const byte ch, const byte val) It sends values to the lamp/s using DmxSimple library

PCB (printed circuit boards):

I used a double faced PCB for that reason approx. 25 pass through rivets or pins are used to solve routes for whole circuit. There are also 5 alignment spots holes to make at first. I designed on every PCB face these 5 alignment spots. In download section you have all PCB files, components and solder faces, mirrored, for downloading and printing by the way of a laser printer on "yellow" or "blue" sheets; I used the blue ones but also the yellow ones are good and the price is lower. I have to say the blue sheets are better... When printing remember to disable toner saving settings, use instead 1200 dpi resolution to have deep real black result. The toner transfer process from magic sheets to PCB is made by the use of an hot iron... Around in the Net there are some tutorials showing how to produce a good PCB but remember these important points: clean perfectly and slightly brush the copper with a kitchen ruvid sponge, 5 minutes of ironing, cold water thermal shock, two faces alignment by the way of 5 holes (I used 5 pins on a large white LED surface to see holes), protect with transparent adhesiv tape the other face during corrosion process. Printing also components designs makes the project "professional" and more simple to place them correctly :-)

Five pins for PCBs faces alignment

After the PCB board is made, first of all place and solder the rivets both faces, then is the time of all top components face; the last is the bottom components: 4 sliders and 4 LEDs. Connect also external components, potentiometer, the push button and the XLR connector to the correct pin number 1, 2 and 3. I installed the small push button vertically with two pins soldered on the PCB, the other 2 pins are connected to other two solder spots just to keep it in place more strongly when pressing it.

Usually I make the plastic box by myself projecting and printing it with a 3D printer but this time the box is larger then my printer capabilities, so I had to buy one. To put everything inside this plastic box is tricky. If you are a Tetris good player it can be helpful! I lets you playing around... let me know :-D

-----------------------------------

NOTES & Improvements:

13.03.2021 : to complete the project I prepared three 3D .STL models at this link https://grabcad.com/library/components-for-dmx-rgb-box-1 where you may download files regarding: a cover panel to place under the sliders and surrounding LEDs, a 18mm tube mounting support (it needs 4 of them) and a ring to put around the push button.

Enjoy with lights and music!

Code

Base DMX Arduino code

/*
  This sketch acts as basic DMX lights controller, 5 channels, RGB and STROBO, by Marco Zonca, 2/2021
  Arduino Nano as 5V MPU, C25B TTL/RS485 rtx board, 4 x 10k slider potentiometers,
  one button, 10k potentiometer, RGB led, 3 x LED and a few resistors;

  Channels: 1=brightness
            2=Red
            3=Green
            4=Blue
            5=STROBO (0-7 none, 8-255 rate)
 */

#include <DmxSimple.h>

#define IS_DEBUG false

byte MaxChannel = 5;
bool isSTROBO = false;
bool ledStroboOn = false;

const byte TTL485Pin = 3;
const byte TrimStroboPin = 15; 
const byte TrimRedPin = 16; 
const byte TrimGreenPin = 17; 
const byte TrimBluePin = 18; 
const byte TrimBrightnessPin = 19; 
const byte LedRPin = 11; 
const byte LedGPin = 10; 
const byte LedBPin = 9; 
const byte ButtonRSPin = 7;

const unsigned long refreshRate = 200;  // millis, lower this for a quicker response at changes
const unsigned long ledStroboRate = 250;  // millis, change this for a different led blinking rate
const byte antiBouncing = 1;  // units, change this to 0 for a better granularity of changes
                              // but more rtx traffic, or increase to 2 if you experience jumping values
const byte chStrobo=5;
const byte chBrightness=1;
const byte chRed=2;
const byte chGreen=3;
const byte chBlue=4;


int ValStrobo=0;
int ValRed=0;
int ValGreen=0;
int ValBlue=0;
int ValBrightness=0;
int prevValStrobo=0;
int prevValRed=0;
int prevValGreen=0;
int prevValBlue=0;
int prevValBrightness=0;

unsigned long lastRefresh = 0;  // millis
unsigned long lastStrobo = 0;  // millis

void setup() {
  if (IS_DEBUG) Serial.begin(38400);
  DmxSimple.usePin(TTL485Pin);
  DmxSimple.maxChannel(MaxChannel);
  pinMode(LedRPin, OUTPUT);
  pinMode(LedGPin, OUTPUT);
  pinMode(LedBPin, OUTPUT);
  pinMode(ButtonRSPin, INPUT);
  pinMode(TrimStroboPin, INPUT);
  pinMode(TrimRedPin, INPUT);
  pinMode(TrimGreenPin, INPUT);
  pinMode(TrimBluePin, INPUT);
  pinMode(TrimBrightnessPin, INPUT);
}//setup()


void loop() {
  readButtons();
  readTrimmers();
  if ((lastRefresh+refreshRate) < millis()) {
    if (isSTROBO==true) {
        if ((ValStrobo < (prevValStrobo-antiBouncing)) || (ValStrobo > (prevValStrobo+antiBouncing))) {
          writeDMX(chStrobo, ValStrobo);
          if (IS_DEBUG) Serial.print("STROBO=");
          if (IS_DEBUG) Serial.println(ValStrobo);
          prevValStrobo=ValStrobo;
        }
    }
    if ((ValRed < (prevValRed-antiBouncing)) || (ValRed > (prevValRed+antiBouncing))) {
      writeDMX(chRed, ValRed);
      analogWrite(LedRPin,ValRed/4);
      if (IS_DEBUG) Serial.print("Red=");
      if (IS_DEBUG) Serial.println(ValRed);
      prevValRed=ValRed;
    }
    if ((ValGreen < (prevValGreen-antiBouncing)) || (ValGreen > (prevValGreen+antiBouncing))) {
      writeDMX(chGreen, ValGreen);
      analogWrite(LedGPin,ValGreen/4);
      if (IS_DEBUG) Serial.print("Green=");
      if (IS_DEBUG) Serial.println(ValGreen);
      prevValGreen=ValGreen;
    }
    if ((ValBlue < (prevValBlue-antiBouncing)) || (ValBlue > (prevValBlue+antiBouncing))) {
      writeDMX(chBlue, ValBlue);
      analogWrite(LedBPin,ValBlue/4);
      if (IS_DEBUG) Serial.print("Blue=");
      if (IS_DEBUG) Serial.println(ValBlue);
      prevValBlue=ValBlue;
    }
    if ((ValBrightness < (prevValBrightness-antiBouncing)) || (ValBrightness > (prevValBrightness+antiBouncing))) {
      writeDMX(chBrightness, ValBrightness);
      if (IS_DEBUG) Serial.print("Brightness=");
      if (IS_DEBUG) Serial.println(ValBrightness);
      prevValBrightness=ValBrightness;
    }
    lastRefresh=millis();
  }
  if (isSTROBO==true && (lastStrobo+ledStroboRate) < millis()) blinkLed();
}//loop()

void blinkLed() {  // led blinking
  if (ledStroboOn==false) {
      analogWrite(LedRPin,ValRed/4);
      analogWrite(LedGPin,ValGreen/4);
      analogWrite(LedBPin,ValBlue/4);
      ledStroboOn=true;
    } else {
      analogWrite(LedRPin,0);
      analogWrite(LedGPin,0);
      analogWrite(LedBPin,0);
      ledStroboOn=false;
  }
  lastStrobo=millis();
}//blinkLed()

void readButtons(){
  if (digitalRead(ButtonRSPin) == LOW) {
    if (isSTROBO==false){
        prevValStrobo=0;
        isSTROBO=true;
      } else {
        writeDMX(chStrobo, 0);  // stop Strobo
        if (IS_DEBUG) Serial.print("STROBO=");
        if (IS_DEBUG) Serial.println(ValStrobo);
        analogWrite(LedRPin,ValRed/4);
        analogWrite(LedGPin,ValGreen/4);
        analogWrite(LedBPin,ValBlue/4);
        ledStroboOn=false;
        isSTROBO=false;
    }
    if (IS_DEBUG) Serial.print("isSTROBO=");
    if (IS_DEBUG) Serial.println(isSTROBO);
    delay(250);
  }
}//readButtons()

void readTrimmers(){
  // instead of mapping 0-1023 I use 10-1013 to reach limits 0-255 easily
  ValStrobo=map(analogRead(TrimStroboPin),10,1013,8,255);
  if (ValStrobo < 8) ValStrobo=8;
  if (ValStrobo > 255) ValStrobo=255;
  ValRed=map(analogRead(TrimRedPin),10,1013,0,255);
  if (ValRed < 0) ValRed=0;
  if (ValRed > 255) ValRed=255;
  ValGreen=map(analogRead(TrimGreenPin),10,1013,0,255);
  if (ValGreen < 0) ValGreen=0;
  if (ValGreen > 255) ValGreen=255;
  ValBlue=map(analogRead(TrimBluePin),10,1013,0,255);
  if (ValBlue < 0) ValBlue=0;
  if (ValBlue > 255) ValBlue=255;
  ValBrightness=map(analogRead(TrimBrightnessPin),10,1013,0,255);
  if (ValBrightness < 0) ValBrightness=0;
  if (ValBrightness > 255) ValBrightness=255;
}//readTrimmers()

void writeDMX(const byte ch, const byte val) {
  if (ch > 0 && ch <= MaxChannel ) DmxSimple.write(ch, val);
  if (IS_DEBUG) Serial.print("sent ");
  if (IS_DEBUG) Serial.print(ch);
  if (IS_DEBUG) Serial.print(" ");
  if (IS_DEBUG) Serial.println(val);  
}//writeDMX()

Credits

Marco Zonca

12 projects • 43 followers

"From an early age I learned to not use pointers"

DMX RGB Mixer for Lights