Wireless Visual Sensor Networks (WVSNs) have been designed to meet strict hardware requirements for wireless sensor network deployments in indoor and outdoor scenarios .
In particular, cameras for outdoor deployment have been designed with power efficiency as one of their main design requirements. They also address the need for intelligently distributing available bandwidth to all the nodes in the network, especially in the case of dense deployments .
Besides utilizing efficient hardware, WVSNs must also follow certain design criteria to satisfy performance requirements imposed by running applications while maximizing the systems lifetime by being energy efficient .
In particular, surveillance of public spaces requires not only efficient resource utilization to maximize service lifetime and availability, but also needs to ensure data being collected is handled in a secure way due to privacy concerns.
To meet time and cost constraints SlugCam has been designed with readily available off-the-shelf devices to reduce cost and allow for rapid development.
Unlike existing smart cameras that run solely on battery as their energy source, we have designed SlugCam to run efficiently on solar power while leveraging a rechargeable battery when sunlight isn’t available. Another important design consideration was to ensure sufficient on-board processing capabilities which allows SlugCam to perform visual processing tasks locally, and thus be more selective of the video it records and transmits, which in turn contributes to power efficiency.
SlugCam’s on-board camera is normally off and gets turned on by a passive infrared (PIR) sensor when motion is detected.
This program allows the MSP430 the ability to monitor the passive infared sensor for motion, and to power on the SlugCam system using a dual coil relay. SlugCam also uses the MSP430 to then keep the SlugCam system awake by using an MSP430 on board timer(32Khz crystal). SlugCam communicates how long it wishes to stay awake using serial SPI communication. Should motion be a nusence, SlugCam also has the ability to tell the MSP430 to ignore the motion interupts for a longer period of time. Also using the msp430’s available RTC clock library the msp430 can also act as the systems clock by monitoring and syncing it.