This project was inspired by the DMX controllers, allowing for scenes using LED RGB lighting. However, I feel DMX is overkill for simple RGB LED Strips, like the AspectLED AL-SL-WR-U-RGBA.
I wanted to control the LED strips from a PLC, without using a DMX programmer or driver. My idea was to use a Raspberry Pi to read from a PLC and send RGB color schemes to an Arduino thru USB to Serial connection. The Arduino would then use PWM outputs to drive a MOSFET for each of the RGB channels.
The RPi would also allow the user to set the color schemes through a Web Interface.
All programming in the RPi would done with Node.js and javascript. The Arduino would, of course, use the Arduino IDE and a sketch.
- Raspberry Pi Model 3 B+
- Elegoo EL-CB-001 UNO R3 Board ATmega328P ATMEGA16U2 with USB Cable for Arduino Check it out here...
- Diymore 4 Channels 4 Route MOSFET Button IRF540 V2.0 + MOSFET Switch Module for Arduino Check it out here...
- A powered USB Hub any brand with at least a 2.5 amp power supply.
- USB Cable (A-Male to B-Male)
- USB cable (A-Male to Micro B Male)
I used this guide to help me get a service set up on the RPi. First I created plc2piard-led.service in /etc/systemd/system/. The article, also, shows how to deploy automatically using GitHub or GitLab.
[Unit]
Description=LED Controller
After=network.target
[Service]
ExecStart=/home/pi/code/plc2piard-led/app.js
Restart=always
User=pi
# Note RHEL/Fedora uses 'nobody', Debian/Ubuntu uses 'nogroup'
Group=pi
Environment=PATH=/usr/bin:/usr/local/bin
Environment=NODE_ENV=production
WorkingDirectory=/home/pi/code/plc2piard-led
[Install]
WantedBy=multi-user.target
Important: You must add #!/usr/bin/env node to the top of your project entry point.
i.e. app.js. Then make it executable with chmod +x app.js.
One of the issues I ran into was that after the service initiated, I received an error from the serialport module.
Error: can't open device "/dev/ttyACM0": Permission denied
With the help from the Arduino.cc forum, I found this helpful snippet.
`In a terminal, with the board plugged in, enter. ls -l /dev/ttyACM*, this will show the group that has access to the port.
Example: crw-rw-r-- 1 root dialout ... /dev/ttyACM0, root is owner, dialout is the group with >access.
Entering the command, groups, in a terminal will show the groups you belong to.
sudo adduser YourUserName GroupToJoin Will fix things if you need to join a group, logout and >login after you run adduser.`
Just using sudo chmod a+rw /dev/ttyACM0 worked until I rebooted, the permissions were not persistent after a reboot on a USB port.
This is an image of a PCB to allow the Arduino nano to plug into the the driver board. The diver board replaces the Diymore prototype board and removes the need for any wiring between it and the Arduino.
