Arduino Temperature Monitor Hub for Klipper

README.md

Arduino Temperature Monitor Hub for Klipper

I wanted to monitor temperatures in certain areas on my printer¹ with Klipper and came up with the following solution.

BoM

Assumes you have access to soldering iron etc.

• Arduino or similar
• Jumper wires
• 10K Ohm resistors
• 10K Ohm NTC Thermistors (I bought some cheap ones from aliexpress²)
• Some kind of 2 pin male + female connectors (optional)

Assembly

Each sensor requires the following circuit ³:

Finished product

Setup

⚠️ Source code has constants/variables that needs to be configured according to your setup.

1. Flash the board with firmware
2. Install serial monitor
3. Set up systemd service
4. Set up Klipper configuration

Screenshots

Footnotes

1. https://gist.github.com/andersevenrud/7e08c67768e7ccdc97df01d3fd034e1d ↩

2. https://www.aliexpress.com/item/4000129976831.html?spm=a2g0o.order_list.order_list_main.30.36f21802RBywhF ↩

3. https://projecthub.arduino.cc/Marcazzan_M/how-easy-is-it-to-use-a-thermistor-81ae74 ↩

firmware.ino

// Flash this onto an Arduino or compatible device

#define RT0 10000  // Thermistor Ω
#define B 3977     // Thermistor K
#define R 10000    // Resistor Ω
#define VCC 5      // Supply voltage

// Adjustable variables
#define DELAY 1000
#define TOTAL 6

int thermistorPins[TOTAL] = { A0, A1, A2, A3, A4, A5 };

float readVoltage(int pin) {
  float VRT = analogRead(pin);    // Acquisition analog value of VRT
  return (5.00 / 1023.00) * VRT;  // Conversion to voltage
}

float convertVoltage(float VRT) {
  float VR = VCC - VRT;
  float RT = VRT / (VR / R);  // Resistance of RT
  float ln = log(RT / RT0);
  float T0 = 25 + 273.15;                  // Celsius to kelvin
  float TX = (1 / ((ln / B) + (1 / T0)));  // Temperature from thermistor
  return TX - 273.15;                      // Conversion to Celsius
}

float readThermistor(int pin) {
  float VRT = readVoltage(pin);
  float TX = convertVoltage(VRT);
  return TX;
}

void setup() {
  Serial.begin(9600);
}

void loop() {
  for (int i = 0; i < TOTAL; i++) {
    float TX = readThermistor(thermistorPins[i]);
    long Kv = round(TX * 1000); // Converted to format Klipper understands natively

    Serial.print(Kv);
    if (i < TOTAL - 1) Serial.print(" ");
  }
  Serial.println("");
  delay(DELAY);
}

monitor.service

# file: /etc/systemd/system/temp-monitor.service
# installation: systemd enable temp-monitor.service
#               systemd start temp-monitor.service

[Unit]
Description=Arduino Temp Monitor

[Service]
ExecStart=/home/klipper/temp-monitor/monitor.sh
WorkingDirectory=/home/klipper/temp-monitor/
RestartSec=10
Restart=always
StandardOutput=syslog
StandardError=syslog
SyslogIdentifier=temp-monitor
User=klipper
Group=klipper
Environment=PATH=/usr/bin:/usr/local/bin

[Install]
WantedBy=multi-user.target

monitor.sh

#!/usr/bin/env bash
# file: /home/klipper/temp-monitor/monitor.sh
# installation: chmod +x /home/klipper/temp-monitor/monitor.sh

# Adjustable variables
DEST=`pwd`/dev
PORT=/dev/serial/by-id/usb-1a86_USB2.0-Ser_-if00-port0
TOTAL=6

while read -r LINE < $PORT; do
  COUNT=$(IFS=' '; set -f -- $LINE; echo $#)

  if [[ $COUNT -eq $TOTAL ]]; then
    I=0
    for VALUE in $LINE; do
      FN="$DEST/$I"
      echo "$VALUE" > $FN
      I=$((I+1))
    done
  fi
done

printer.cfg

# Append this to the Klipper configuration file

[temperature_sensor stepper_x_casing]
sensor_type: temperature_host
sensor_path: /home/klipper/temp-monitor/dev/0

[temperature_sensor stepper_y_casing]
sensor_type: temperature_host
sensor_path: /home/klipper/temp-monitor/dev/1

[temperature_sensor stepper_z_casing]
sensor_type: temperature_host
sensor_path: /home/klipper/temp-monitor/dev/2

[temperature_sensor stepper_e_casing]
sensor_type: temperature_host
sensor_path: /home/klipper/temp-monitor/dev/3

[temperature_sensor printer_intake]
sensor_type: temperature_host
sensor_path: /home/klipper/temp-monitor/dev/4

@rrosin

but I will try to add the Arduino as a second MCU.

That would be pretty sweet. It didn't actually cross my mind when I set this up :)