ThermoWatch – Raspberry Pi Pico Enclosure Thermometer (OLED + NTC)

ThermoWatch is a compact, screw-together enclosure for a Raspberry Pi Pico thermometer. A 0.96" OLED in the lid shows the temperature inside your 3D-printer enclosure, measured by a 100k NTC thermistor on a long cable. Power comes from the printer PSU (6.5–28 V) through an MP1584 step-down module.

FEATURES

• Every part is screw-mounted – no glue, no snap fits

• 12 × M3 heat-set inserts with M3 socket head screws

• Pico held by a pocket, two lips and a clamp bar – USB stays accessible for programming

• OLED sits in a recess behind the lid window and is held by a clamp frame

• Strain relief for the power and sensor cable

• Mounting tabs left and right for wood/chipboard screws

• All parts print without supports – the STLs are already in print orientation

• Size: 129 × 57 × 36 mm (box 99 × 57 mm)

PRINTED PARTS

• Base (Unterteil.stl) – print upright

• Lid (Deckel.stl) – top face down

• OLED clamp frame (Rahmen_OLED.stl)

• Pico clamp bar (Klemme_Pico.stl)

• MP1584 bridge (Bruecke_MP1584.stl)

• Cable clamp (Klemme_Kabel.stl)

Print settings: PETG recommended (it sits next to a warm enclosure), PLA works too · 0.2 mm layers · 4 walls · 20 % infill · no supports

HARDWARE

• 12 × M3 heat-set insert, 5.0 mm outer diameter (holes are 4.2 mm – adjust if your inserts differ)

• 6 × M3 × 8 socket head screw (lid, OLED frame)

• 6 × M3 × 10 socket head screw (clamps)

• 4 × 4 × 20 mm countersunk chipboard screw (mounting tabs)

The full bill of materials is in the parts list image.

ELECTRONICS

• Raspberry Pi Pico (no headers)

• MP1584EN step-down module with JST XH 2-pin input pigtail

• 0.96" I²C OLED (SSD1306, 128 × 64)

• 100 kΩ NTC thermistor (β 3950) on a long cable

• 47 kΩ 1 % resistor + 100 nF ceramic capacitor

• Optional: 1N5819 Schottky diode (only if USB and the MP1584 are connected at the same time)

WIRING – all on the right pin row of the Pico

• Pin 39 VSYS ← MP1584 OUT+ (5.0 V)

• Pin 38 GND ← MP1584 OUT−

• Pin 36 3V3(OUT) → OLED VCC

• Pin 35 ADC_VREF → NTC

• Pin 33 AGND → 47 kΩ + 100 nF

• Pin 31 GP26/ADC0 → NTC + 47 kΩ + 100 nF

• Pin 28 GND → OLED GND

• Pin 27 GP21 → OLED SCL

• Pin 26 GP20 → OLED SDA

See the wiring diagram image for details.

FIRMWARE

Arduino IDE with the "Raspberry Pi Pico/RP2040/RP2350" board package by Earle Philhower and the Adafruit SSD1306 + Adafruit GFX libraries. The sketch (ThermoWatch_Arduino.ino, attached) shows the current temperature with min/max, detects a broken sensor cable and shifts the screen content every minute to prevent OLED burn-in. The calibration values are at the top of the sketch; the serial monitor (115200 baud) prints the measured NTC resistance.

ASSEMBLY

1. Set the MP1584 output to 5.0 V with a multimeter BEFORE connecting the Pico.

2. Melt in all heat-set inserts.

3. Solder the wires to the Pico. Solder the 47 kΩ resistor and the 100 nF capacitor directly between pin 31 and pin 33.

4. Slide the USB end of the Pico under the two lips, lower it into the pocket and fix it with the clamp bar.

5. Place the MP1584 in its pocket and fix it with the bridge.

6. Put the OLED into the lid recess and screw on the clamp frame.

7. Route the power and sensor cable through the right wall and fix them with the cable clamp.

8. Close the lid and mount the enclosure using the tabs.

Tighten the clamp screws hand-tight only – they press directly on the PCBs.