Introduction: 4CH Relay-board Controlled With Push Buttons
My goal is to upgrade my Anet A8 3D-printer by adding a power supply control via the Octoprint interface. Nevertheless, I also want to be able to start "manually" my 3D-printer, meaning not using the web interface but just pressing a button.
Step 1: The Wiring
The AC-DC PSU is connected with a Smart-plug (TP-Link) which is controllable by means of a smartphone (App Kasa) or a button.
This PSU power the Raspberry Pi 3 B+ by means of a LM2596 DC-DC Buck Converter Module (12V - 5V). The 4-Relay Module 5V with Optocoupler Low-Level-Trigger is directly connected to the RPI 3B+ (no need of 3.3V tuning).
4 Push buttons are connected as "pull-up resistor" to the RPI 3B+.
For the wiring, just have a look to the sketch.
Step 2: The Software
For the control by means of push-buttons, I've used Python to write the program, inspiriting me by reading the following thread:
To insure the interaction with the control via Octoprint, there is a test to check the current status of the relay and change it.
The script is attached.
Comments: As the Relay 1 controls the motherboard, I wanted to add a security by switching off with the push-button. The goal was to maintain the button pressed during 5 seconds to confirm the switch-off. Unfortunately, the script works but not reliably due to rebound effect. If you have a correction to suggest feel free to share it.
To make the script executable: sudo chmod 777 /home/pi/script/Relay_board_control.py
To test the script: ./Relay_board_control.py
To copy the script: sudo cp Relay_board_control.py /usr/local/bin
To run automatically the script at the start:
sudo nano /etc/rc.local
add the path to the script "/home/pi/scripts/Relay_board_control.py &" between fi and exit 0
For the control by means of Octoprint, it's well documented on the web.
There is two steps:
1- Edit the /etc/init.d/octoprint file by adding in the block "do_start()" just after RETVAL="$?:
gpio export 6 out
gpio -g write 6 1
gpio export 13 out
gpio -g write 13 1
gpio export 19 out
gpio -g write 19 1
gpio export 26 out
gpio -g write 26 1
2- Edit the /home/pi/.octoprint/config.yaml file by adding the block "System":
- action: Printer_ON
command: gpio -g write 6 0
- action: Printer_OFF
command: gpio -g write 6 1
confirm: You are about to turn_OFF the printer.
- action: LED-String_ON
command: gpio -g write 13 0
- action: LED-String_OFF
command: gpio -g write 13 1
- action: LED-Cam_ON
command: gpio -g write 19 0
- action: LED-Cam_OFF
command: gpio -g write 19 1
- action: Relay-4_ON
command: gpio -g write 26 0
- action: Relay-4_OFF
command: gpio -g write 26 1
Step 3: The Test
The behavior of the push-buttons is a bit tricky but after a few trials you get it.
Step 4: Finalize the Concept
Now I will solder the push-buttons on a perfboard and add a 5 pins connector.
Finally, I have designed and print 2 cases:
- one for the RPI 3 B+ and the relay-board
- one to cover the wiring at the base of the PSU and to fix the LM2596 DC-DC Buck Converter Module.
You can find the *.stl and *.gcode files on www.thingiverse.com