Scardey Ghost

thingiverse

The ghost gets terrified when trick-or-treaters arrive at the door, and it will conceal its eyes, hoping that the frightening monsters will vanish. I draped a gauze-like cloth over the frame, allowing the PIR sensor to see through it. The cloth must be securely tied to the frame; otherwise, the PIR sensor may mistake the motion of the cloth for an approaching person and trigger the arms to close. I programmed the system so that one arm will perform a brief scan before closing if it detects someone is still present. This prevents the arms from flapping excessively. The flat spots on the servo arms are not long enough to accommodate the servos, which was intended to provide additional strength when poking the arms into place. An Arduino Nano powers this system without header pins, and wires connect to a dual-row header that supports the servos at the back. The Tower Pro 9g servos, widely available, and the HC-SR501 PIR sensor, costing under a dollar, are used in this setup. The sensitivity of the PIR sensor is significantly reduced, enabling it to detect only when someone is directly in front. I secured the cloth with zip ties at key points, though hot glue might have been a more effective choice as it would be less visible from outside. A USB breakout cable was built since the regulator on the Arduino Nano struggled to power both servos reliably. The 5V from the USB cable is directly connected to the servo header pins.