Game feeder controller
Posted on May 29, 2012 8564
The circuit is built around an LM339 quad comparator, Ul, which forms the basis of a Schmitt trigger, timer circuit, and a window comparator. One comparator within the LM339 (pins 1, 7, 6), plus LDR1, R4, R5, R6 and R8, is used as a Schmitt trigger. The timer circuit (which receives its input from the Schmitt trigger) consists of R9, RIO, Rll, R13. The last two-fourth's of Ul (pins 8, 9, 10, 11, 13 and 14) are wired as a window comparator. The two inputs to the window comparator are derived from the charge on capacitor Clâ€”which is fed to pins 9 and 10 of Ul. The other inputs are picked from two points along a voltage-divider network, consisting of Rl, R2, and R3.
DiodeD1 is used as a blocking diode, forcing capacitor Cl to discharge through RIO and R13. The window comparator looks for any voltage falling between one-third and two-thirds of the supply voltage. When the voltage falls between those two points, the output of the window comparator (pins 13/14) goes high. Transistors Ql, and Q2 are turned on, when the pins 13/14 junction goes high, energizing the relay, Kl. The energized relay provides a dc path to ground, activating the motor, Ml, which reloads the feeder. The timer circuit also provides immunity from triggering, duei;o lightning. The on-time of relay Kl is determined by the charge cycle of Cl, Rll, and R9 or the discharge cycle of Cl, RIO, and R13. Changing the value of either a resistor or the capacitor, changes the timing cycle.