January 2006, Issue 186

Electronic Scarecrow

EVENT TRIGGERS

The heart of the Electronic Scarecrow is its output triggering system, which collects the sensor trigger status from all the remote units and decides whether or not to activate a countermeasure. The system is highly configurable. Different sensors can be enabled at different times of day. The system can specify whether or not multiple activations are required within a certain time interval and whether or not the activations must come from different sensors or the same one. Listing 1 shows the routine that implements this trigger logic.

There can be up to eight virtual output channels, each having different triggering parameters and driving one of the various outputs. Several channels can drive the same output. This can be useful for playing back sounds. During the day, you can set activation to a single sensor with a 5-s sound duration. In the evening, you can set multiple activations with a shorter sound duration in order to keep the peace with your neighbors. You can also trigger each channel manually. The available settings are listed in Table 1.