With a careful balance of hardware and firmware, sensor systems can be built that deliver extended battery life.
The unique features of the DRV5000 family of Hall effect sensors, combined with the ultra-low power capabilities of the MSP430TM MCU, enable for the first time, smart physical presence-detection systems such as door or window security, and e-meters to remain directly powered from a single low cost CR2032 coin cell for over two decades of continuous operation.
Compared to an always-active sensor system, an intelligent Hall-effect sensor system can be designed with its current consumption reduced from what are typically milliamps to less than a microamp — a reduction of over 1000x. This is achieved by combining the fast start-up time and wide-range operating voltage of the DRV5000 Hall sensor with the ultra-low-power capabilities of the MSP430 MCU. Such a sensing system with extremely low power consumption enables physical presencedetection applications, such as door or window security systems, and e-meters to be directly powered from a single low-cost CR2032 coin cell for over two decades of continuous operation.
The techniques described in this paper that enable ultra-low power (ULP) sensing include:
- Operating the system in ultra-low power standby mode as the normal mode
- Duty-cycling the sensor
- Exercising power-aware firmware
The simplified example circuit in Figure 1 shows a very low-cost system that does not require any external calibration. The complete sub-microamp, intelligent Hall-sensing system detects the presence of a magnet and is powered directly from a CR2032 battery.
