The giant (by radio control standards) servos above are shown adjacent to a Nokia 3310 mobile phone to give an idea of the scale. The arms are 12cm long - perfect for lifting a bank of solar panels (wing). Our local Model Aerodrome in Seaside Road, Eastbourne, supplied these beauties, taking the trouble to source one unit from afar - not the kind

of thing you are asked for every day. Thanks to Dave and Steve for helping us out of a tough spot. The Model Aerodrome were also able to match a reduction gearbox shown elsewhere on this site under catamaran model drive-train. On this page we also look at two electronic design solutions for control of our wing angle. One is an analogue comparator based circuit, the other a digital computer chip based circuit. They both do the same thing, but with different features. The LED arrangement in the LM339 circuit below uses two rows of three LEDs with each LED connected in parallel, the two rows are connected in parallel but reversed polarity. The sensor array is made with three west LEDs and three east LEDs. A 1meg resistor and a 10n ceramic capacitor (103z) are also in parallel with the sensor. The sensor LEDs provide input voltage for two comparators on the LM339 chip with the variable resistor R2 providing a "dead zone" or sensitivity adjustment. Each comparator output is fed into a transistor Darlington pair which in turn drives the DC motor. The rail voltages are provided by two batteries connected in series with the center tap providing the ground reference. The developers at Green Watts have tested this circuit with 2 single cell lithium-ion batteries providing +/- 4. 2 volts and two 12 volt lead batteries, the LM339 is rated for input voltages from +/- 2 volts to +/- 18 volts. This special COMPUTER CHIP CONTROLLED SOLAR...

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