Low Voltage Smart Scale Power Supply – Design It Right!
Smart scales require stable low-voltage power (typically 3.3V or 5V) for accurate weight sensing and Bluetooth/wireless communication. But powering them efficiently from standard sources like USB or Li-ion batteries can be tricky.
⚠️ The Problem: Voltage Drops = Sensor Errors
If the power supply is noisy or drops below the operating range, the load cell amplifier (e.g., HX711) or microcontroller (like ESP32) can behave erratically. This affects readings, display output, or wireless syncing.
🔧 The Fix: Use LDOs or Buck Converters
To step down 5V or Li-ion battery (3.7–4.2V) to 3.3V reliably:
Use a Low Dropout Regulator (LDO) like AMS1117 for simplicity.
Or use a buck converter for better efficiency if current > 300mA.
💡 Real-Life Example
A hobbyist in Pune building a smart kitchen scale faced issues with fluctuating readings. Switching from an unstable linear supply to a buck converter module fixed it instantly.
🔢 Sample Calculation
Powering an ESP32 (max 240mA) and HX711 (10mA):
Total current ≈ 250mA.
For AMS1117 (dropout ~1.1V), input must be ≥4.4V.
So a Li-ion cell at 3.7V won’t work—use a buck converter instead!
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