🛠 Nœud capteur autonome sur batterie : énergie et fiabilité

Objectives

Powering a Zero W on battery: 65 × 30 mm and ~150 mA typical during activity (including radio) make it an ideal sensor node — with one major pitfall.

Hardware

• 1 Raspberry Pi Zero W + a quality 5 V USB battery (power bank)
• 1 5 V / 1.2 A power supply for debugging
• I²C sensor (the header provides 3.3 V, SDA1/GPIO2, SCL1/GPIO3)

Steps

1. Measure your actual profile with a USB tester (~150 mA with Wi-Fi active, more depending on peripherals). A 5000 mAh battery gives an order of magnitude of 30 h at a constant 150 mA — to be adjusted for the duty cycle.
2. Disable unused services (sudo systemctl disable --now cups avahi-daemon) and sample in short cycles: read, post via HTTP, sleep.
3. Protect the SD card: mount /var/log in tmpfs, group synchronizations at the end of the cycle.
4. Monitor temperature in a sealed enclosure: vcgencmd measure_temp — throttling at 80 °C, limit 85 °C.

Verification

Full cycle with a USB tester: peak < 500 mA, average consistent with the calculated autonomy.

Common errors

• Power bank entering sleep mode under low load: "low-current" model.
• Black enclosure in direct sunlight: at ~0.75 W, solar heat is enough to reach 80 °C.