Photosensitive security system for theft detection and control using GSM technology This paper illustrates the design and development of a theft control system for security lockers, homes, bank lockers, jewelry outlets, etc. The proposed system consists of an LDR (Light Dependent Resistor) based sensor which acts as an electronic eye for detecting the theft or attempt, and a signaling procedure based on SMS using GSM (Global Systems for Mobile communications) technology. The GSM based communication helps the owner and concerned authorities to take necessary and timely action in order to prevent the theft. The LDR circuit is interfaced using a relay circuit with an Arduino microcontroller board. Efficacy of the proposed system can be seen in its immediate intimation regarding the incident. The proposed designed system is very effective and inexpensive.