LILYGO T-Higrow ESP32 Smart Plant Sensor (DHT11, Soil Moisture, Light, Fertility)

Specifications

• Microcontroller: ESP32 (Dual-core, up to 240 MHz)

• Flash Memory: 4MB

• PSRAM: None

• Wireless: 2.4 GHz Wi-Fi (802.11 b/g/n) & Bluetooth v4.2 BR/EDR and BLE

• Temperature & Humidity Sensor: DHT11 (Wired to GPIO16)

• Ambient Light Sensor: BH1750 (I2C: SDA IO25, SCL IO26)

• Soil Moisture Sensor: Capacitive (Wired to IO32)

• Soil Fertility (EC) Sensor: Conductive Nodes (Wired to IO34)

• USB-to-Serial Chip: CH9102

• Power Interface: USB Type-C & JST 1.25mm Battery Connector

Key Applications and Projects

• Automated Smart Greenhouses: Integrating the T-Higrow with Home Assistant. When the soil moisture drops below a specific threshold, the ESP32 triggers a smart relay to activate a drip irrigation pump automatically.

• Houseplant Health Dashboards: Pushing temperature, light, and moisture data to a Grafana or ThingsBoard dashboard to visually track the historical health of delicate exotic plants.

• Botanical Alert Systems: Programming the board to send a Telegram message or push notification to your phone when your plant needs watering or fertilizer.

Unlock New Capabilities (Project Evolution) The Talking, Thirsty Plant: Give your favorite houseplant a personality! Because the T-Higrow is built on the ESP32, you can easily interface it with external hardware. Solder a small MP3 decoder module and a speaker to the T-Higrow's exposed GPIO pins. Program the ESP32 so that when the capacitive soil sensor reads a critically low moisture level, the plant literally "speaks" to you as you walk by, playing an audio file saying, "Hey, I'm thirsty! Please water me!"

PACKAGE INCLUDED

• 1 x LILYGO T-Higrow Board (with DHT11)

• 1 x JST 1.25mm Battery Power Cable

• 2 x Male Pin Headers (Unsoldered)

Downloads & Links

• LILYGO T-Higrow Board Github Link

FREQUENTLY ASKED QUESTIONS (FAQ)

1. What microcontroller drives the T-Higrow? It is powered by the Espressif ESP32 dual-core microprocessor.

2. How does the soil moisture sensor work? The long, black lower half of the board uses capacitive sensing. It measures changes in capacitance caused by the dielectric permittivity of the surrounding soil (which changes based on water content).

3. Why is capacitive sensing better than resistive? Cheap resistive sensors pass an electrical current directly through the soil via exposed metal prongs, which causes rapid corrosion and destroys the sensor within weeks. Capacitive sensors are coated in solder mask and do not expose bare metal to the wet soil (except for the tiny EC nodes at the very tip), drastically increasing their lifespan.

4. What do the two metal dots at the tip do? Those two exposed nodes are the EC (Electrical Conductivity) sensor, also known as the fertility sensor. They measure the conductivity of the soil to estimate the concentration of salts and nutrients (fertilizer).

5. How far should I insert the board into the soil? You should insert the black "spear" portion into the soil up to the white line printed on the PCB. Do not submerge the electronic components on the upper half of the board.

6. Is the top half of the board waterproof? No. The upper half housing the ESP32, DHT11, and light sensor is completely exposed. If you are using this outdoors or in an environment where you spray water, you must design or 3D print a protective cover for the top half.

7. What is the DHT11 used for? The blue DHT11 component measures the ambient temperature and humidity of the air surrounding the plant. It does not measure soil temperature.

8. What is the BH1750 used for? The BH1750 is a digital ambient light sensor. It measures the intensity of light (in lux) hitting the plant, allowing you to determine if it is getting enough sun.

9. How do I power the T-Higrow? You can power it via the USB Type-C port, or you can attach a 3.7V Lithium Polymer (LiPo) battery to the JST connector on the back.

10. Does the board charge the battery? Yes, if a LiPo battery is attached to the JST port, plugging in a USB-C cable will safely charge the battery.

11. How do I read the battery level? The board usually has a voltage divider circuit routed to an ADC pin (often GPIO 35 or 33, check specific board revision) allowing you to monitor the battery voltage in your software.

12. How do I program this board? You connect it to your computer via the USB Type-C port. This specific version uses the CH9102 USB-to-Serial chip. You may need to download the CH9102 drivers for your operating system if the port does not appear.

13. What settings should I use in the Arduino IDE? Select the standard "ESP32 Dev Module". You can program it using Arduino C++, MicroPython, or ESPHome.

14. Are there any physical buttons? Yes, there are physical Reset and Wake buttons located on the side edges of the board.

15. How do I access the data on my phone? You can write custom code to push the sensor data to a cloud service (like Blynk, ThingSpeak, or an MQTT broker) and view it on a companion app, or you can use LILYGO's provided example firmware and mobile application.

16. Which pins are the sensors connected to? According to the pinmap: The DHT11 is on GPIO16, the BH1750 uses I2C (SDA 25, SCL 26), Soil Moisture is on IO32, and Soil Fertility is on IO34.

17. Do I need to calibrate the soil moisture sensor? Yes. Capacitive sensors provide raw analog values. You must write a simple sketch to read the value when the sensor is completely dry (in the air) and completely submerged in a glass of water. You then map those two extremes to 0% and 100% in your final code.

18. What logic voltage does the board use? Like all ESP32 microcontrollers, the GPIO pins operate strictly on 3.3V logic.

19. What are the unpopulated pin holes on the side for? These break out power (5V, 3V3, GND) and unused GPIO pins, allowing you to solder the included headers and attach external modules like relays or MP3 players.

20. My computer doesn't recognize the board. Why? First, ensure your USB-C cable is a data cable, not just a charging cable. Second, ensure you have installed the CH9102/CP210X serial drivers for your OS.