ShroomBox is an open-source IoT mushroom-fruiting chamber published on Hackster.io in June 2022. Its ESP32 controller combines temperature, humidity, CO₂ and moisture sensing with 12-volt heating, humidification, ventilation and lighting, while a Blynk dashboard provides monitoring and manual or automatic control. The project is best understood as an educational maker build—not a finished commercial appliance.
Its strongest ideas are integrated sensing, CO₂-aware ventilation, PWM control and selectable operating modes. Its important weaknesses are equally clear: the documented ultrasonic humidifier was unreliable, and the chamber can heat but cannot actively cool. Those limitations matter more than the phone dashboard when deciding whether to reproduce or modernize the design.
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What problem does ShroomBox solve?
Fruiting mushrooms require a managed balance of relative humidity, temperature, fresh-air exchange, CO₂ concentration, light and consistent observation. A plastic chamber can provide the enclosure, but it does not automatically maintain the conditions inside it. Manual misting and ventilation can work for a small grow, yet they become inconsistent when the room temperature changes or the grower cannot check the chamber frequently.
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ShroomBox addresses that problem by connecting environmental sensors to an ESP32 and using the readings to operate low-voltage actuators. Its Blynk interface adds remote visibility, settings, charts and manual controls. Automation reduces repetitive checking; it does not replace species-specific cultivation knowledge. The correct conditions still depend on the species and strain, substrate, chamber volume, room temperature, airflow and fruiting stage.
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The original project is intended for fruiting colonized mushroom blocks or similar substrates. It is not an incubation system, sterilizer or laboratory clean room. A chamber should be described as cleanable, sanitized and contamination-managed. Contamination control begins with substrate preparation and handling, not merely with filtered chamber air.
See the original Hackster project for the published files, photographs, schematics and firmware context.
How the system is arranged
The control architecture is straightforward:
SHT30, SCD30, DS18B20, moisture sensor
↓
ESP32
↙ Wi-Fi ↘
Blynk app MOSFET drivers
↓
12 V heaters · humidifier · fan · LED stripThe ESP32 reads the chamber and room conditions, applies configured rules, and drives the 12-volt loads. Wi-Fi connects the controller to Blynk for telemetry and commands. Local control should remain primary: a network outage must not leave heaters or a humidifier running indefinitely.
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Controller and power
- ESP32-DEVKITC-32D: the Wi-Fi-enabled microcontroller board.
- 230 V AC to 12 V DC, 20 A supply: the main source for the low-voltage loads in the documented design.
- DC/DC step-down converter: reduces 12 V to 5 V for the ESP32 development board.
- Custom PCB: provides the connectors, sensor interfaces and actuator-driver arrangement.
- Fuses and screw terminals: protect and distribute the power wiring, with additional tubular fuses on the heating-pad supply wiring.
The specified supply has substantial current capacity because the original design includes two 12 V, 50 W heating pads as well as a fan, LED strip and humidifier. Actual supply sizing must be based on the measured startup and continuous current of the particular loads used.
Sensors
- SHT30: chamber temperature and relative humidity over I²C.
- SCD30: CO₂ concentration over I²C.
- DS18B20 probes: room temperature and heating-pad temperature over OneWire.
- SEN0193 capacitive soil-moisture sensor: substrate-moisture measurement.
- Photoresistor input: provided for possible future light sensing.
The original sensor selection is more comprehensive than a basic humidity controller. It attempts to distinguish chamber conditions, room conditions, heater temperature, CO₂ and substrate moisture. That does not mean every measurement is equally useful in every grow. A substrate-moisture probe is not a universal proxy for mushroom hydration, and the reading can vary with substrate composition, probe placement and corrosion or contamination.
Actuators
The documented loads are two 12 V heating pads, an ultrasonic humidifier, a 12 V LED strip and a 12 V fan. IRLZ34N MOSFETs provide PWM control for appropriate 12 V DC loads, allowing variable power rather than simple on/off switching.
PWM is useful for a DC fan, heater or LED strip when the device is designed to tolerate it. It is not automatically suitable for every ultrasonic humidifier. Some humidifiers contain internal electronics that expect a stable supply. Depending on the unit, a relay, dedicated driver or external control input may be safer than rapidly switching its supply.
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- Dual-Core Performance Up to 240 MHz: Run sensor processing, wireless communication, automation logic and connected-device tasks on a 32-bit dual-core ESP32 platform designed for responsive embedded and IoT projects
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- USB-C Programming with CP2102: Connect through USB-C for power, sketch uploads and serial monitoring, while GPIO, UART, SPI and I2C interfaces support sensors, displays, motor drivers and other modules (USB-C cable not included)
- Over-the-Air Update Support: Configure OTA functionality through a compatible ESP-32 software framework to update deployed firmware over Wi-Fi without reconnecting the board by USB for every revision
Building the chamber
The mechanical design uses a plastic storage box with a fan cutout, separate airflow openings, micro-filter provisions, cable glands, 3D-printed fan protection and airflow covers. An internal aluminum table can be removed or lifted to separate the mushroom blocks from the chamber floor. The LED lighting is mounted in or on the lid, while the humidifier and water reservoir are arranged externally and feed moisture into the chamber.
This layout has practical advantages. The tank can be reached without opening the fruiting space, the blocks are raised away from standing water, and printed covers can protect fingers and redirect airflow. It also creates several points requiring careful construction: penetrations must be sealed without trapping water, filters must remain serviceable, and the humidifier route must not become a condensation drain into the electronics.
Sensor placement is part of the design
The SHT30 should be positioned away from the humidifier outlet and heat sources. The SCD30 is placed in the lower portion of the chamber in the original build, but its reading still depends on chamber geometry and air mixing. An external temperature probe can also be influenced by the chamber’s heat even when it is outside the box.
A sensor can report plausible numbers while the fruiting bodies experience different conditions. Fog striking the humidity sensor, condensation on its surface, heat from electronics, stagnant corners and a fan’s short-circuited intake-to-exhaust path can all produce misleading data. Validate readings against visible condensation, surface moisture, mushroom morphology and airflow—not against a single number alone.
Humidification: the main unresolved subsystem
The original design uses an ultrasonic humidifier in an external tank and routes moisture into the chamber. The project reports that an initial 10 mm pipe did not provide enough flow and that condensation and sealing were problematic. It also acknowledges that the ultrasonic humidifier remained unreliable and needed improvement.
That is not a minor footnote. A humidity controller is only as reliable as its water-delivery path. Before operating unattended:
- Keep the tank and humidifier accessible for cleaning and refilling.
- Use clean water and establish a repeatable cleaning schedule.
- Add a baffle or settling chamber so droplets do not hit the mushrooms directly.
- Keep the fog path away from the ESP32, PCB, connectors and power supply.
- Provide a route for condensation and prevent water from pooling near cable penetrations.
- Use humidity hysteresis, minimum run times and maximum continuous-on timers.
- Consider an external fogger, evaporative humidifier or controlled misting system if the ultrasonic arrangement proves unstable.
Some secondary coverage suggests 85–95% RH for many oyster and lion’s-mane grows, but that is not a universal target. Follow the requirements for the particular species, strain and fruiting stage rather than copying a generic range. The 2026 secondary explainer also describes generalized alternatives, but its suggested parts and timed controls should not be confused with the original 2022 hardware.
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Fresh air and CO₂ control
The original ShroomBox uses CO₂ feedback to regulate fan output and includes hysteresis-based control. In simplified form, the fan turns off below a lower CO₂ threshold and on above an upper threshold. The gap between those thresholds prevents rapid switching when the reading hovers around one value.
Fresh air and humidity compete physically. More ventilation can improve CO₂ conditions but also dry the chamber and fruiting surfaces. Too little exchange may contribute to elongated stems, poor cap development or stalled fruiting; too much can cause drying. The fan should not blow directly at the mushrooms, and intake and exhaust openings should promote mixing rather than a short route across the sensor.
Filters can reduce dust and insects, but they also restrict airflow as they load. A CO₂ sensor near the floor may detect local accumulation without representing the whole chamber. Sensor response time, fan cycles and chamber volume all affect the reading. Treat thresholds as tunable control parameters and compare them with observed growth, not as universal biological constants.
This differs from the simplified timed-fan approach described in secondary coverage. Timers are easier to implement, but CO₂-based control can respond to the actual load in the chamber—provided the sensor is placed and calibrated sensibly.
Electrical architecture and safety
The documented power path is:
- 230 V AC enters a 12 V DC, 20 A power supply.
- The 12 V rail feeds the heating pads, fan, humidifier and LED strip.
- A DC/DC converter produces 5 V for the ESP32 development board.
- The ESP32 supplies sensors with 3.3 V where appropriate.
- IRLZ34N MOSFETs switch or PWM-control suitable 12 V loads.
- Fuses protect the low-voltage distribution and heater branches.
Although most loads operate at 12 V, the input side is mains-powered and the chamber is wet. Use an enclosed, certified external power supply where possible. Provide strain relief, drip loops, grounding where applicable, correctly rated fuses, insulated terminals and a nonconductive separation between water paths and electronics. Use GFCI/RCD protection appropriate to your jurisdiction. Readers without mains-electrical experience should have the mains side assembled or inspected by a qualified person.
12 V is lower risk than mains voltage, but it is not harmless: high-current wiring can overheat, short circuits can cause fire, and heating pads require appropriate branch protection. Do not place a bare power supply or exposed PCB in the fog path.
Blynk interface and operating modes
The original firmware is based on Blynk Edgent and supports Wi-Fi provisioning through the Blynk app or a local web address. A reset button can clear stored Wi-Fi credentials so the device can be configured for another network.
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The project exposes three modes:
- OFF: active outputs are disabled while measurements continue to be sent.
- MAN: the user sets actuator PWM values manually.
- AUTO: temperature, humidity, CO₂ and lighting are regulated using configured parameters.
The interface includes a home screen, automatic settings, growth-phase selection, actuator status, sensor values, charts and an advanced terminal for setting PWM values. Separate settings for two growth phases allow the grower to change control parameters without rebuilding the firmware.
These labels and workflows describe the original implementation. Blynk’s current product, device-template process, widgets, provisioning flow and plan structure may differ from the 2022 platform. Check the current Blynk site and current pricing page before committing to a new build. Do not assume that a historical statement that the project used a free version still describes current availability or limits.
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At startup, the firmware initializes the sensors, disables active outputs, retrieves stored Wi-Fi information and enters provisioning mode when credentials are unavailable. It periodically sends sensor readings to Blynk and receives user commands through Blynk callbacks. Automatic control uses PWM and hysteresis.
Hysteresis matters because a value hovering at a threshold can otherwise switch an actuator repeatedly. Rapid cycling creates electrical noise, unnecessary wear and unstable environmental conditions. A more robust modern implementation should add:
- Range checks for every sensor.
- Stale-data and sensor-disconnect detection.
- Maximum humidifier-on duration.
- Minimum on/off times for fans and heaters.
- Heater shutdown on a high-temperature fault.
- Safe output states after a controller reset or sensor failure.
- Local automatic operation when Wi-Fi or Blynk is unavailable.
- Connection-fault logging and user alerts when communications return.
The source is described as a PlatformIO project for Visual Studio Code and includes the Blynk connection code. Treat the published firmware as a starting point to inspect and adapt, not as a safety-certified controller.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.What ShroomBox does—and does not—solve
| It provides | It does not guarantee |
|---|---|
| Integrated environmental sensing | Uniform conditions throughout the chamber |
| Remote monitoring and control | Reliable operation during every network failure |
| CO₂-aware fan regulation | Correct species-specific cultivation parameters |
| Heating, humidification, lighting and ventilation outputs | Active cooling in a warm room |
| Open-source firmware, PCB and mechanical files | Sterilization, contamination prevention or improved yield |
The authors note that the chamber works better in colder rooms because it can heat but cannot cool. In a warm room, the heaters may be unnecessary or harmful. A modern system should define a high-temperature response: disable heaters, increase ventilation where appropriate, notify the user, or add an independent cooling system.
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The project’s claims that automation can simplify cultivation or improve yield should be treated as goals or expectations. The available project description does not provide a controlled comparison, baseline, yield dataset or statistical evidence proving better production.
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- 2.4GHz Dual Mode WiFi + Bluetooth Development Board
- Ultra-Low power consumption, works perfectly with the Arduino IDE
- Support LWIP protocol, Freertos
- SupportThree Modes: AP, STA, and AP+STA
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Should you reproduce or modernize it?
Reproduce the original when
- You want an open-source educational project.
- You specifically want CO₂-based ventilation.
- You are comfortable with a custom PCB and 3D-printed parts.
- You can safely build an enclosed 12 V distribution system with mains isolation.
- You value OFF, MAN, AUTO and growth-phase modes.
Simplify it when
- You are growing only one or two blocks.
- A humidity controller and timed fan are sufficient.
- You do not need substrate-moisture sensing, heating pads or remote PWM control.
- You prefer an enclosed commercial power supply, off-the-shelf MOSFET module and no custom PCB.
Modernize it when
- The chamber will run unattended.
- You need active cooling or operation in a warm room.
- Humidity reliability, local fallback and fault alarms are important.
- You want better water/electrical separation, watchdog recovery and historical data.
- You are implementing the current Blynk workflow rather than reproducing a 2022 setup unchanged.
A practical modernization can retain the ESP32 and the overall sensor-to-controller-to-actuator architecture while replacing the humidification path, adding interlocks and using a current Blynk device configuration. Newer humidity-temperature sensors may also be appropriate, but they should be selected and protected for high humidity rather than exposed directly to fog.
Troubleshooting guide
Humidity reads high, but mushrooms look dry
Move the SHT30 away from the fog outlet and inspect for stratification, blocked filters and direct fan flow. Check surface moisture where the fruiting bodies are located, not only the sensor value. A humidifier can create a wet sensor pocket while the rest of the chamber remains dry.
The fan dries the chamber too quickly
Reduce duty cycle, increase the CO₂ hysteresis band, add minimum off-time and allow humidity recovery between ventilation cycles. Recheck intake and exhaust sizing and prevent the fan from blowing directly at the blocks.
CO₂ never falls
Confirm that the fan is actually receiving the intended PWM signal and current, inspect filters and openings, and check for short-circuiting between intake and exhaust. Allow time for the SCD30 reading to respond and verify that its position samples mixed chamber air.
The humidifier runs continuously
Check the humidity sensor for fog or condensation, validate its wiring and readings, and add a maximum-on timeout. If the chamber does not gain humidity, inspect the tube, seals, baffle and reservoir. Continuous operation should result in a fault state rather than an unattended flood risk.
Blynk disconnects
Test local control independently of the app, inspect provisioning and Wi-Fi credentials, and make sure automatic rules continue without cloud connectivity. Use the reset procedure to clear credentials only when you are ready to provision the device again.
Sensor values freeze or become implausible
Check I²C wiring and addresses for the SHT30 and SCD30, OneWire wiring for the DS18B20 probes, supply voltage, condensation and cable strain. Implement stale-data detection and shut down dependent actuators when a critical sensor fails.
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Heaters overshoot
Use the pad-temperature DS18B20 as an independent protection signal, reduce PWM, widen temperature hysteresis and add a hard high-temperature cutoff. Never rely on the phone dashboard as the only heater safety mechanism.
Bottom line
ShroomBox is a strong open-source reference for building an ESP32-controlled mushroom fruiting chamber with Blynk. Its documented combination of SHT30, SCD30, DS18B20 and SEN0193 sensors, 12 V PWM loads, custom PCB and selectable control modes gives makers a useful architecture to study and adapt. It is not a validated production controller or a plug-and-play appliance. Reproduce it for the learning value and CO₂-aware control; simplify it for a small grow; or modernize it if unattended operation, reliable humidification, active cooling and fault recovery are essential.
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