Voron Chamber Temperature Sensor — BME280, NTC, and Klipper Config

Electronics Mod Klipper

Why Add a Chamber Temperature Sensor?

A Voron with an enclosed chamber benefits greatly from active chamber temperature monitoring. Benefits include:

• Print consistency — ABS/ASA parts require a stable chamber temperature (45-60℃) for optimal layer adhesion and warp prevention. Knowing your chamber temp lets you adjust print start delays and part cooling fan behavior.
• Heat creep prevention — If the chamber exceeds 60-65℃, heat creep into the hotend heatbreak becomes a risk. A chamber sensor can trigger a warning or shut down the print if the chamber gets too hot.
• Enclosure heater control — If you use a chamber heater (e.g., a silicone heater pad or a Nevermore with heater), the chamber sensor is required for closed-loop temperature control.
• Filter fan triggering — The Nevermore carbon filter or other chamber filter fans can be controlled based on chamber temperature (e.g., turn on when chamber is above 40℃).
• Diagnostics — A sudden chamber temperature drop indicates an enclosure leak or a door left open. A rapid rise indicates a heater runaway. Both are worth knowing about.

BME280 vs NTC Thermistor — Sensor Comparison

Recommendation: Use a BME280 if you want humidity data and higher accuracy. Use an NTC thermistor if you have a spare analog input on your MCU and only need basic temperature monitoring. The BME280 is the preferred choice in the Voron community because humidity data is valuable for drying filament and managing enclosure conditions.

Wiring the BME280 to Your Voron MCU

I2C Connection (Standard)

The BME280 connects via I2C. Most BME280 breakout boards use 3.3V logic and need 3.3V power (not 5V). Wiring:

BME280 Board   ->   MCU Pin (e.g., Octopus / Spider / SKR)
VCC (3.3V)     ->   3.3V pin
GND            ->   GND
SDA            ->   I2C_SDA (e.g., PB7 on Octopus, PE0 on Spider)
SCL            ->   I2C_SCL (e.g., PB6 on Octopus, PE1 on Spider)

Important: Some BME280 boards have a built-in voltage regulator and can accept 5V on VCC. Check your specific board. If in doubt, use 3.3V. Connecting a 3.3V-only BME280 to 5V will damage it.

Pull-up resistors: I2C requires pull-up resistors on SDA and SCL (typically 4.7kΩ). Most BME280 breakout boards include these. If your board does not (rare), add 4.7kΩ resistors from SDA to 3.3V and SCL to 3.3V.

I2C Address Selection

The BME280 has two possible I2C addresses, selected by the SDO pin:

• SDO connected to GND: address 0x76 (default for most boards)
• SDO connected to VCC: address 0x77

If you have multiple I2C devices, ensure each has a unique address. Most BME280 modules come with SDO pre-connected to GND (address 0x76).

Wiring an NTC Thermistor

An NTC thermistor uses a simple voltage divider with a pull-up resistor. Wiring:

NTC Thermistor (one leg) -> ADC pin on MCU (e.g., PA0, PC0)
NTC Thermistor (other leg) -> GND
Pull-up resistor (4.7kΩ) -> from ADC pin to 3.3V

Klipper handles the voltage reading and temperature conversion natively using the thermistor model. You define it in the config (see below).

Note: Most Voron MCU boards have internal pull-up resistors that can be used instead of an external resistor. However, using an external 4.7kΩ resistor is more reliable and consistent. For a 100kΩ NTC (most common for Voron), a 4.7kΩ pull-up gives good resolution in the 20-80℃ range.

Sensor Mounting Locations

Optimal Location: Near the Print Volume, Not the Heated Bed

The sensor should measure the air temperature around the print, not the bed surface temperature. Mount it:

• On the gantry (recommended) — Attach the sensor to the X/Y gantry using a printed mount. This places it near the print area. The gantry moves so the sensor averages chamber temperature well. Gantry mounts are available on Printables/Thingiverse for most Voron models.
• On the rear extrusion — Mount the sensor to the rear vertical extrusion, about 100mm above the bed. This gives a stable reading that represents the average chamber temperature, though slightly biased toward the back of the chamber.
• On the Nevermore filter — If you have a Nevermore, mount the sensor inside the Nevermore housing or on its exhaust path. This gives a reading of the recirculated air temperature, which is relevant for filter performance.
• On the top panel — Not recommended. Hot air rises, so the top of the chamber is 5-15℃ warmer than the print area. The temperature reading will not represent conditions at the print.

Critical: Do not mount the sensor directly above the bed heater, in direct line of the bed's radiant heat. The sensor will read the bed temperature rather than the air temperature. Keep at least 50mm horizontal offset from the bed edge.

Klipper Config for BME280

Add this to your printer.cfg to enable the BME280 as a chamber temperature sensor:

[temperature_sensor chamber_bme280]
sensor_type: BME280
i2c_address: 118  # 0x76 in decimal (or 119 for 0x77)
i2c_bus: i2c1     # Depends on your MCU wiring
i2c_mcu: mcu      # Main MCU, or use "host" for Raspberry Pi GPIO
# Optional:
# min_temp: 0
# max_temp: 100

Important: The i2c_bus parameter varies by MCU and wiring:

• i2c1 — Octopus Pro, Spider (I2C on PB6/PB7)
• i2c2 — Octopus v1.1
• i2c0 — SKR boards (some models), or when using SCL/SDA on specific pins
• host — When connecting to Raspberry Pi GPIO (pins 3 and 5). Requires Linux i2c-dev and i2c-tools installed.

To find the correct i2c_bus on your MCU, run this in the Klipper terminal:

# List available I2C buses on the MCU
I2C_SCAN

This will show you which I2C bus has a device at the BME280 address. Use that bus in your config.

Klipper Config for NTC Thermistor

Add this to your printer.cfg to use an NTC thermistor as a chamber sensor:

[temperature_sensor chamber_ntc]
sensor_type: Generic 3950  # Or ATC Semitec 104GT-2, or similar
sensor_pin: mcu:PA0        # Replace with your ADC pin
pullup_resistor: 4700      # External pull-up resistor value in ohms
# Optional:
# min_temp: 0
# max_temp: 100

Common NTC thermistor types for chamber monitoring:

• Generic 3950 — 100kΩ NTC with B=3950. Very common, accurate enough for chamber monitoring.
• ATC Semitec 104GT-2 — High-precision 100kΩ NTC. Used in E3D V6 hotends. Excellent accuracy.
• NTC 100K B3950 — Same as Generic 3950. Widely available on Amazon/AliExpress.

Using a Raspberry Pi GPIO for the BME280 (Host-Based)

If your MCU does not have a spare I2C port or you prefer to keep chamber sensor wiring separate, connect the BME280 to Raspberry Pi GPIO (pins 1=3.3V, 3=SDA, 5=SCL, 6=GND).

Config:

[temperature_sensor chamber_bme280]
sensor_type: BME280
i2c_address: 118
i2c_bus: host
# No i2c_mcu needed — Klipper reads the sensor via Linux I2C on the Pi

On the Raspberry Pi, enable I2C:

# In terminal:
sudo raspi-config
# Navigate to Interface Options -> I2C -> Enable
# Then reboot

# Verify the sensor is detected:
sudo i2cdetect -y 1
# Look for 0x76 (or 0x77) in the output

If you see "UU" or "76" at the expected address, the sensor is detected and ready.

Chamber Temperature Display and Monitoring

Once configured, the chamber temperature appears in:

• Mainsail — Automatically shown in the temperature card if you have a temperature_sensor section.
• Fluidd — Same, shown alongside hotend and bed temperatures.
• KlipperScreen — Add the sensor to the display config in KlipperScreen.conf.
• Moonraker — The sensor data is available via Moonraker API for custom dashboards.

To verify the sensor is working:

# In Klipper terminal:
STATUS
# Look for the sensor name and reading in the output

# Or via Moonraker API:
curl http://localhost:7125/printer/objects/query?temperature_sensor_chamber_bme280

Chamber Monitoring Macros

Here are useful Klipper macros for chamber temperature management:

Warm-Up Wait Macro

Wait for the chamber to reach a minimum temperature before starting a print. Useful for ABS printing:

[gcode_macro WAIT_FOR_CHAMBER_TEMP]
gcode:
  {% set target_temp = params.TARGET|default(50)|int }
  {% set max_wait = params.MAX_WAIT|default(1800)|int }  # Default 30 min
  {% set start_time = printer.moonraker_current_time|int }
  {% while printer.temperature_sensor_chamber_bme280.temperature < target_temp }
    {% set elapsed = printer.moonraker_current_time|int - start_time }
    {% if elapsed > max_wait }
      { response('WARNING: Chamber did not reach ' ~ target_temp ~ ' in ' ~ (max_wait/60)|int ~ ' minutes') }
      { break }
    {% endif }
    G4 P5000  # Wait 5 seconds
  {% endwhile }
  { response('Chamber reached ' ~ target_temp ~ '℃') }

Use in your START_PRINT: WAIT_FOR_CHAMBER_TEMP TARGET=50

Chamber Overheat Protection

Stop the print if chamber temperature exceeds a safe limit (heat creep risk):

[gcode_macro CHECK_CHAMBER_TEMP]
gcode:
  {% set max_temp = params.MAX|default(65)|int }
  {% set current_temp = printer.temperature_sensor_chamber_bme280.temperature }
  {% if current_temp > max_temp }
    { response('CRITICAL: Chamber temperature ' ~ current_temp ~ ' exceeds ' ~ max_temp ~ '℃. Emergency stop.') }
    M112  # Emergency stop
  {% endif }

Call this periodically in your print loop or in a delayed G-code timer.

Nevermore Fan Control by Chamber Temp

Automatically control Nevermore filter fans based on chamber temperature:

[gcode_macro NEVERMORE_AUTO]
gcode:
  {% set chamber_temp = printer.temperature_sensor_chamber_bme280.temperature }
  {% if chamber_temp < 40 }
    M106 P3 S0     # Turn off Nevermore fan (fan 3)
  {% elif chamber_temp < 50 }
    M106 P3 S128   # 50% speed
  {% else }
    M106 P3 S255   # 100% speed
  {% endif }

Humidity Monitoring with BME280

One of the benefits of BME280 over NTC is humidity data. You can expose humidity via a virtual sensor or use it in macros:

[temperature_sensor chamber_bme280]
sensor_type: BME280
i2c_address: 118
i2c_bus: i2c1
# Klipper natively shows temperature only (not humidity)
# To get humidity data, use Moonraker's sensor API or a custom Python script

For humidity monitoring, you can create a Moonraker update agent or use sensor_pin + a custom Python script. Alternatively, use Home Assistant + Moonraker integration to display both temperature and humidity from the BME280.

Practical use: If chamber humidity is above 40-50%, filament stored in the enclosure (especially nylon, PC, PVA) will absorb moisture. Use humidity data to decide if you need to run a filament dryer before printing.

Common Issues and Troubleshooting

Issue: Sensor Shows 0℃ or -273℃ (Invalid Reading)

Causes: I2C address wrong, I2C bus wrong, wiring issue, sensor not powered.

Fixes: Verify the I2C address (use I2C_SCAN in Klipper terminal). Check wiring — SDA and SCL swapped is a common mistake. Ensure the sensor has power (3.3V to VCC). Try the other I2C address if using address 0x76 fails.

Issue: Sensor Reading Fluctuates Wildly

Causes: Loose wiring, electrical noise on I2C lines, sensor too close to the bed heater, or a defective sensor.

Fixes: Check JST connector crimps on the sensor cable. Shorten the I2C cable (keep under 30cm for reliable I2C). Add a ferrite bead on the sensor cable. Move the sensor away from the bed heater. Replace the sensor module.

Issue: NTC Reading is Inaccurate

Causes: Wrong thermistor type selected in config, pull-up resistor value mismatch, or self-heating from too much current through the thermistor.

Fixes: Verify the thermistor B value matches the config. A 3950 thermistor with B=3950 config should be accurate within ±2℃. Check the pull-up resistor — use a 4.7kΩ resistor for a 100kΩ NTC. If the thermistor reads high, self-heating may be the cause — reduce pull-up to 10kΩ or use a thermistor with higher resistance.

Issue: I2C_SCAN Shows No Device

Causes: I2C not enabled on the MCU, wrong i2c_bus parameter, sensor not powered, or wiring fault.

Fixes: Enable I2C in your MCU firmware. Verify 3.3V at the sensor. Check SDA/SCL wiring. Pull SDA and SCL to 3.3V with 4.7kΩ resistors if not on the breakout board. Try the host-based approach (Raspberry Pi GPIO) if MCU I2C is problematic.