A compact, inexpensive monitor that uses a repurposed bathroom scale, HX711 amplifier, and ESP32 to measure salt in a water softener’s brine tank and provide alerts when salt levels are low.
- Purpose: Sits beneath the brine tank to measure total salt weight.
- Key Design Choices:
- Utilizes an old bathroom scale: budget-friendly, durable, non-invasive.
- HX711 amplifier is mounted inside—minimizes analog noise over cable runs.
- Load cells arranged in a Wheatstone bridge (front-left + rear-right, front-right + rear-left) for balanced readings.
- A single Ethernet cable carries:
- 5 V supply (input at scale via DC barrel jack).
- 3.3 V power (regulated by ESP32) fed down to HX711.
- HX711 data lines (SCK, DT) and ground.
- Advantages:
- Clean, tidy, modular wiring.
- Consolidated power input at the scale simplifies cable management.
- Hosted in a 3D-printed enclosure with magnetic mounting to the resin tank.
- Contains:
- ESP32 microcontroller – handles data processing and logic.
- OLED display – shows salt weight continuously.
- Buzzer – emits periodic beeps when salt weight drops below ~25 lb (configurable alert threshold).
- Pushbutton – initiates calibration routines on demand.
- LDR (light-dependent resistor) – turns off the display in low-light for power saving and burn-in prevention.
- Adding wireless connectivity (e.g., Wi-Fi, Bluetooth) to enable remote salt level alerts (e.g., via Telegram, email).
- Logging salt usage trends over time to predict refill needs.
- Customizing alert thresholds or adding smartphone integration.
- Instructables Guide: Detailed build walkthrough and steps
- Source Firmware:
SaltScale_V2.ino