Mellow FLY PT100 Thermistor Board 3.3V/5V SPI | Voron Marlin

Mellow FLY PT100 Stick Thermistor Board – 3.3V/5V SPI Interface

Upgrade your Voron or other 32-bit 3D printer's temperature sensing with the Mellow FLY PT100 Stick Thermistor Board (Model: 20PT100SB). Originally designed by Raymond H, this compact add-on board plugs directly into a stepper driver port and communicates via SPI, giving your hotend ultra-accurate PT100 RTD temperature readings without requiring a dedicated thermistor input. Made in Mainland China.

Key Features

• Dual voltage support: Works at both 3.3V and 5V — an upgrade over the original 3.3V-only design, giving compatibility with a wider range of mainboards.
• SPI Interface: Communicates over the stepper driver port's SPI bus (MOSI, MISO, SCK, CS), requiring no extra wiring harness.
• 32-bit board compatible: Designed for 32-bit motherboards running Klipper or Marlin 2.0.7.2 and later.
• PT100 RTD accuracy: Supports PT100 platinum resistance temperature sensors with a 430Ω sampling resistor for precise hotend temperature monitoring.
• Multi-sensor support: Use up to two PT100 sensors simultaneously by inserting boards into separate driver ports (e.g., E4 and E5) and configuring CS1/CS2 pins independently.
• Plug-and-play installation: No assembly required — simply insert into the driver port (with port jumpered to SPI mode) and configure firmware pin definitions.
• Voron ready: Ideal for Voron builds and other high-performance printer platforms that demand accurate high-temperature sensing.

Specifications

Firmware Setup Overview (Marlin)

1. Jumper the target driver port (e.g., E5) to SPI mode.
2. Insert the PT100 stick board into the driver port correctly.
3. Open the firmware and locate the motherboard's pin definition header (pins.h).
4. Identify the SPI pin assignments (e.g., MOSI=PB15, MISO=PB14, SCK=PB13) and the CS pin for your chosen driver port.
5. Define the communication pins:

   #define THERMO_SCK_PIN  PB13
   #define THERMO_DO_PIN   PB14
   #define THERMO_CS1_PIN  PB12
   #define THERMO_CS2_PIN  -1
   #define MAX31865_MOSI_PIN  PB15
       

6. Set the first nozzle thermistor type to -5 (PT100) with a sampling resistance of 430.
7. Compile and upload firmware to your mainboard.

For Klipper configuration and detailed wiring diagrams, refer to the official GitHub repository for the FLY PT100 board.

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Frequently Asked Questions

Q: Is the Mellow FLY PT100 Stick Board compatible with Klipper firmware?

A: Yes, the Mellow FLY PT100 Stick Thermistor Board is fully compatible with Klipper firmware in addition to Marlin 2.0.7.2 and later versions. It requires a 32-bit mainboard with an accessible SPI-mode driver port (such as E4 or E5) and proper pin configuration in the firmware.

Q: Can I use two PT100 sensors at the same time on one mainboard?

A: Yes. You can install two PT100 Stick Boards simultaneously — for example, in the E4 and E5 driver ports. Each port must be jumpered to SPI mode independently, and you configure CS1 and CS2 pins separately in your firmware to address each sensor individually.

Q: What is the difference between this board and the original PT100 stick board design?

A: The original design by Raymond H supports only 3.3V logic. The Mellow FLY version adds 5V support, making it compatible with a broader range of 32-bit 3D printer mainboards that operate at 5V logic levels on their driver ports.

Q: Does this board require any soldering or assembly?

A: No assembly or soldering is required. The PT100 Stick Board is plug-and-play — simply insert it into the correct driver port on your mainboard, set the port jumper to SPI mode, and configure the firmware pin definitions accordingly.

Production & Packaging Notice

To maintain high stock availability and fast shipping times, our items are sourced from multiple verified manufacturing facilities. While the core quality, materials, and product specifications remain identical, you may notice slight variations in the packaging design, manufacturing origin, or the wording of the printed instructions.