Hardware Architecture and Design Details
Overview of the dual-PCB design, including block diagram, schematics, 3D models, and hardware setup
Modular Dual-PCB Hardware Architecture
The hardware platform is based on a dual-PCB design, separating control and communication from power and actuation functions.
PCB No. 1 serves as the main control and communication unit and is the core of every node. It integrates the ESP32-C3 microcontroller, supercapacitors for energy storage, and a DC/DC converter to provide a stable supply voltage for the controller, sensors, and connected modules. The board also features seven Grove-compatible connectors for easy integration of third-party sensors, as well as screw terminals for extending the supercapacitor capacity.
PCB No. 2 is dedicated to power and actuation and is optional, depending on the application. It is required when driving external devices such as water valves or other modules that demand higher voltages and short current bursts. The board includes a boost converter with a 3–5 V input range and selectable output voltages of 9 V, 12 V, or 24 V, delivering up to 2Apeak of output current. In addition, four H-bridge channels enable control of external devices such as valves, actuators, and relays, supporting both positive and negative output voltages.
This modular approach allows the system to be tailored to a wide range of applications, from low-power sensing nodes to more demanding actuator-driven systems.
Block Diagram
Technical Specifications
PCB No.1 – Control and Communication
Energy storage:
- Onboard 2x supercapacitors 22F/2.8V
- Expandable with an additional pair of supercapacitors (screw terminal connection)
Solar panel input:
- Default 5V/60mA 45x45mm solar panel
- Expandable with an additional independent power source (decoupled by diodes),e.g., a second solar panel
DC-DC controller:
- Input voltage range: 1.7V-5.5V
- Output voltage: 4V
- Max output current: 2A
Switched Power Outputs:
- GSM/GPRS Modem SIM800L: 4V
- Grove interfaces: approx. 3.3V
Controller:
- Type: ESP32-C3-MINI-1-N4
- External 32 kHz crystal for RTC in deep sleep mode
- Reset button for firmware flashing (prevents entering sleep mode via software)
Programming Interfaces:
- UART (RX, TX, ENABLE, BOOT, supercapacitor voltage)
- USB-C (data + power, 500mA current limited)
Grove interfaces:
- 7x connectors (2xSPI, 2xADC, 2xI2C, 1xUART)
- Supply voltage: approx. 3.3V
- Supply current limited only by DC-DC controller (approx. 2A)
PCB No.2 – Power and Actuation
Boost DC-DC Converter:
- Input voltage range 3.0V – 5.5V
- Max. input current 6A (peak)
- Output voltage: 9V/12V/24V
- Output capacitor approx. 500uF
Max. Output Current:
- 1.5A @ 9V
- 1.0A @ 12V
- 0.5A @ 24V
Outputs:
- 4x H-Bridge outputs (positive, negative, high impedance)
- Overvoltage protection (TVS diodes)
Control:
- I2C commands (4-output variant)
- Digital I/O (1-output variant)