Project 17—Glowing Blinking Eyes
Figure 5-6 Connecting the motor arm to the eyelids
the center of the shutter so that they can be pulled up and down by the motor actuator that will be installed shortly. Cut a small elastic band in half, then tie one end to the center of the shutter. The up and down movement of the eyelid shutter will be delivered by a high-tech rotary actuator with a right-angle drive system—this is also known as a “toy motor” with a bit of copper wire soldered to the shaft. You can use any motor with enough power to lift the shutters up and down using the elastic band as a towing wire, so look for a small electric motor from a kid’s toy. As shown in Figure 5-6, a small actuator arm is made by wrapping a bit of copper wire around the motor shaft then soldering it in place so it does not slip. The elastic is then tied to the end of the actuator arm so that, at full rotation, the eyelids uncover at least 80 percent of the ball halves, and when no power is applied to the motor, the shutters drop back over the eyes. A little experimentation with the length of the copper wire arm and the elastic will be necessary, so make things longer than they need to be at first and trim them down as needed. Also shown in Figure 5-6 is a small wood screw placed at one side of the box to restrict how far down the shutters will travel when there is no
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power applied to the motor to lift the actuator arm. This wood screw stops the eyelids from dropping below the eyes to create a more natural blinking illusion. If you have trouble tying the elastic to either part of the wire, just do your best, then use a bit of hot glue to secure it in place. Now, your motor should be able to lift the eyelids up and down at levels that look like realistic blinking from a distance in the dark. Avoid dropping the 9-volt battery directly across the motor at this point, or you may bend or loosen the copper arm from the torque. It’s best to try the motor on less voltage or through a current limiting resistor of 10 or 20 ohms. The schematic for the eye blinker is shown in Figure 5-7, and it uses a simple 555 timer circuit to drive the motor for about half a second and then repeats the cycle about once a second. This timing cycle can be altered by changing the values of resistors R1 and R2 or by increasing the value of C1 for much longer blink cycles. Resistors R3 and R4 limit the current to both the LEDs and the motor, and should be chosen based on the components you plan to use. If you do not know the current capabilities of the LEDs you have, then start with a higher value for R3 such 1K, and work your way down to increase the