Portable Raspberry Pi Pico Soil Moisture Sensor

I wanted to create a compact rechargeable soil moisture sensor that feels more like a real portable device than a typical prototype.

This device is a rechargeable portable soil moisture monitoring system based on the Raspberry Pi Pico.

It combines:

• Raspberry Pi Pico
• SSD1306 OLED Display
• Capacitive Soil Moisture Sensor v2.0
• TP4056 Charging Module
• NCR18650B Lithium-Ion Battery
• Physical Jumper Power Disconnect
• NCR18650B Battery

The device uses a physical jumper-based hard power disconnect system.

Jumper Installed:

• TP4056 OUT+ connected to Pico VSYS
• Device powered ON

Jumper Removed:

• VSYS disconnected
• Device powered OFF

Advantages:

• Ultra low standby power
• No parasitic drain
• Reliable physical disconnect
• Simple and robust operation

The TP4056 charging board handles:

• Lithium-ion charging
• Overcharge protection
• USB charging via Micro-USB
• System Power Path

Battery → TP4056 → Jumper → Pico VSYS

Bill of Materials (BOM):

Main Electronics:

Component Quantity Description

Raspberry Pi Pico 1 Main microcontroller

SSD1306 OLED 0.96" Display 1 I2C 128x64 white display

Capacitive Soil Moisture Sensor v2.0 1 Analog moisture sensor

TP4056 Charger Module 1 Micro-USB Li-Ion charging board

NCR18650B Battery 1 Rechargeable 18650 Li-Ion cell

18650 Battery Holder 1 Battery mount

2-Pin Header 1 Power disconnect interface

Jumper Cap 1 Physical ON/OFF switch

Mechanical Components:

Component Quantity Description

M2x10 Socket Head Screws 4 Housing assembly screws

Custom 3D Printed Housing 1 Main enclosure

Custom 3D Printed Buttom 1 Integrated sensor mount

Recommended Print Settings:

Setting Value

Layer Height 0.2 mm

Infill 15–20%

Wall Count 5

Material PLA / PETG

Supports Minimal

This project is designed as a compact portable plant monitoring device with integrated charging and low-power operation.

The hardware architecture emphasizes:

• simplicity
• portability
• clean internal integration
• reliable operation
• low idle power consumption
• maker-friendly assembly