Alarm. - Here is Circuit Schematic Musical Doorbell as a Shadow Sensor Alarm using HL-06 (HLS5TA06). Shadow sensor alarms are usually used for protection against theft. A shadow alarm is a device that sounds an alarm when a shadow falls on it. Our shadow sensor alarm unit is capable of sensing a moving shadow in a restricted area, and can be easily installed on a wall, window or door to protect our valuables from theft. Note that constant lighting is required in the confined area to detect the moving shadow. This shadow sensor alarm raises an alert in the form of a distinct musical tone (for a finite duration) whenever a shadow is sensed by the photoresistor (LDR).
|Figure 1. Schematic Musical Doorbell as a Shadow Sensor Alarm|
This is the internal circuit diagram of the doorbell used by me. This unit is built around a small microcontroller HL-06 (HLS5TA06), which is a low cost voice and melody synthesizer with 4-bits CPU. Here, this 14-pin DIL microcontroller is programmed as a 16-Tune English Melody Generator. A PNP transistor (BC557), ofcourse with some supporting components, is connected in the trigger input circuit to trigger the microcontroller HL-06.
From the circuit, I removed the 10K resistor, and soldered a 5mm LDR in that place. Next, I placed a short jumper wire between the points of the AC 230V Trigger Input (you can connect an spst on/off switch in lieu of this jumper to enable/disable the alarm unit). Wow! a compact, fool-proof, battery-operated Shadow Sensor Alarm is ready for use.
The Original article : "Musical Doorbell as a Shadow Sensor Alarm"