Projects / Measurements, sensors and data acquisition
Autonomous strain-gauge measurement node with a 24-bit ADC, GSM data transfer, battery power, solar charging and low-power measurement cycles.
The task was to develop an autonomous measurement node that can work for a long time without external power and send weight or load data to a remote server. The device had to work reliably with a strain-gauge sensor while consuming minimal energy between measurement cycles.
An autonomous weight sensor for remote monitoring was developed. The strain-gauge bridge connects to a 24-bit ADC, the controller manages power for the measurement path and GSM modem, and data is sent to a server. Power is supplied from batteries with solar-panel charging.
Project materials
Engineering context
A strain-gauge measurement path needs stable excitation and low noise.
A GSM modem creates pulsed loads and consumes much more current than the measurement circuitry.
For autonomous operation, the measurement path, modem and voltage dividers have to be physically disabled between cycles.
The system has to monitor battery and solar-panel voltages.
Work done
Autonomous measurement-module circuit design.
Bridge strain-gauge sensor input.
ADS1232 24-bit ADC.
STM32L433 for measurement processing and mode control.
GSM modem for data transfer.
Battery power with solar charging.
Battery and solar-panel voltage monitoring.
Switchable power circuits for energy saving.
Details
The strain-gauge bridge signal is digitized by a dedicated 24-bit ADC. According to the project materials, the electronics provided about 40 g resolution on a two-ton load cell without noticeable noise.
The controller enables the measurement circuitry, voltage dividers, GSM modem and auxiliary nodes only when they are needed. This is essential for a device that has to work from batteries.
GSM communication makes it possible to use the sensor on a remote object without a local operator and without wired infrastructure.
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