PrusaCupHeater

PrusaCupHeater is a project aiming to utilize spare / waste heatbedlets (heat bed tiles) from Prusa XL printer.

The ultimate objective was to build a cup heater that can be powered from USB-C PD power supply and connected to Home Assistant.

Required parts

• Prusa XL Heat Bed Tile (obviously)
• Wemos D1 Mini ESP8266 module (or similar)
• DS18B20 temperature sensor (or any alternative)
• power MOSFET/PWM breakout board
• USB-C PD Trigger with 20V out support
• DC-DC step-down converter (at least 24V input, 5V output)
• optional: 3 LED strip WS2812B
• 3D Printed box

Purchase links

Component/Module	CZ	International
Prusa XL Heatbed tile	prusa3d.com
Wemos D1 Mini	laskakit.cz, pajenicko.cz	Aliexpress
DS18B20 temp sensor	laskakit.cz, pajenicko.cz	Aliexpress
MOSFET module	laskakit.cz	Aliexpress
USB-C PD trigger	laskakit.cz
DC-DC Step-down converter	laskakit.cz, pajenicko.cz	Aliexpress
WS2812 LED strip (60 LED/m; 3 LEDs total)	laskakit.cz, pajenicko.cz

Assembly instructions

• wire up the modules following way:
  • DS18B20 to pin D7 on Wemos D1, glue the sensor to the bottom of the heat bed tile
  • power MOSFET module to pin D1 on Wemos D1
  • (optional) WS2812 to pin D6 on Wemos D1
• jumper the USB-C trigger to output 20V
  • wire 20V out from the PD trigger into the MOSFET switching part
  • connect power pins from MOSFET trigger into the heat bed tile

Firmware instructions

• flash tasmota-sensors into the Wemos D1, you can use Tasmota Web Installer
• apply following template:
  • without WS2812 {"NAME":"PrusaCupHeater","GPIO":[0,0,0,0,0,224,0,0,0,1312,0,0,0,0],"FLAG":0,"BASE":18}
  • with WS2812 {"NAME":"PrusaCupHeater","GPIO":[0,0,0,0,0,224,0,0,1376,1312,0,0,0,0],"FLAG":0,"BASE":18}

Home Assistant configuration

Prerequisite: Tasmota integration working with MQTT server

• if you want to control the Cup Heater via Home Assistant, you need to define a thermostat
• open your configuration.yaml and add following:

  climate:
    - platform: generic_thermostat
      unique_id: prusa_cup_heate
      name: PrusaCupHeater
      heater: switch.tasmota_2
      target_sensor: sensor.tasmota_ds18b20_temperature
      min_temp: 40
      max_temp: 120

Replace switch.tasmota_2 and sensor.tasmota_ds18b20_temperature by relevant heater switch and temperature sensors entities in your setup.

• change Logging interval on your Tasmota to lowest possible value (10s) - Configuration -> Configure Logging -> Telemetry Period

Standalone operation configuration

It is possible to enable simple heating control using Tasmota Rules. To do this, open Tasmota Console and create two rules by entering following commands:

• Rule1 ON Tele-DS18B20#Temperature<55 DO Power1 1 ENDON
• Rule2 ON Tele-DS18B20#Temperature>65 DO Power1 0 ENDON
• enable the rules using following commands:
  • Rule1 1
  • Rule2 1
• if you have WS2812 add third rule to light it up when heating is active:
  • Rule3 ON Power1#State=1 DO Power2 1 ENDON ON Power1#State=0 DO Power2 0 ENDON
  • enable the rule: Rule3 1
• to make it update correctly change Logging interval on your Tasmota to lowest possible value (10s) - Configuration -> Configure Logging -> Telemetry Period

You can adjust target temperature and temperature hysteresis limits as per your requirements. The setup described above has target 60°C while allowing +/-5°C hysteresis. Note: berry scripting is not supported on ESP8266 devices.

To do list

✅ include WS2812b LED strip control

✅ add berry script for autonomous operation

🔲 add pictures to the description

🔲 add wiring diagram

🔲 add touch sensor to control operation

🔲 add 128x32 OLED display with temperature and status reading

🔲 add cup presence detection

🔲 leverage internal thermistor on the heatbed tile instead of DS18B20