Multifunction Human Detection And WEATHER MONITORING SYSTEM

A human detection system was designed earlier to utilise the microwave Doppler effect to detect human movement and trigger AC appliances such as light bulbs and other electrical loads up to 1A. The design incorporated a solder jumper pad for mode selection, enabling the same PCB to be configured for IoT compatibility by integrating IoT functionality into the radar switch. This configuration supports real-time radar data monitoring, alert reception, and wireless control of lights over a WiFi network.

- ASHWINI KUMAR SINHA

Coverage of the IoT code and app development for this system was planned in the previous month. Building on the existing architecture, the software and circuitry required to connect the human radar design to IoT and IIoT dashboards and user interfaces have now been created. On the hardware side, the PCB layout remains essentially unchanged, as the solder pad and FPC connector are already integrated, allowing seamless connection to any IoT board or dedicated industrial interface board.

During earlier testing, it was observed that specific microwave Doppler radar modules available on the market provide insufficient output current to trigger the optotriac in some cases, resulting in difficulty for the optocouplers when switching an AC bulb. To address this behaviour, a solder jumper was included to allow connection to a development board, enabling radar data processing and reliable bulb activation through the board. A buffer circuit or transistor may also be added if such issues arise with a specific radar module.

In most cases, the radar module can directly trigger the VO2223A, as the internal LED requires only a minimal current to activate. The LED forward voltage at 10 mA is typically 1.3-1.4V, allowing the radar module's OUT pin to provide the necessary LED drive current.

For enhanced reliability and compatibility with all RCWL microwave radar modules on the market, a buffer transistor circuit is recommended when direct triggering is not feasible. In this system, the radar output is connected directly to the development board, as testing confirmed reliable performance without a transistor buffer.