Abstract: A hitch control system includes various sensors, an operator command lever, a spring-centered three position raise/lower switch, a control unit which generates control signals as a function thereof and an actuator which moves the hitch in response to the control signals. The control system permits the operator to move the hitch to a working position via manipulation of the command and a single manipulation of the raise/lower switch. The control system ignores switch manipulation unless the manipulation persists for at least a certain time period, or if the switch is manipulated in a different manner within a certain time of the earlier manipulation. In a failure mode the control system permits the hitch to be moved to a working position via manipulation of the raise/lower switch when the command lever cannot be so used.

Abstract: A solenoid current control system includes a microprocessor which periodically generates a desired peak current value and which energizes the solenoid coil. Current through the coil is sensed via a series resistor and the sensed current is compared to the desired peak current by comparator. The comparator generates an interrupt signal when the sensed current reaches the desired peak value. The interrupt signal is applied to the microprocessor which responds by de-energizing the coil.

Abstract: A sensor for counting articles, such as seeds, moving through a conduit includes an array of infrared LEDs generating a uniform diffuse beam of radiation which entirely illuminates a cross sectional volume of the conduit. The beam is detected by a planar photo diode which extends across the opposite side of the conduit. A pair of mirrors extend along opposite sides of the conduit between the array and the photo diodes. Slits narrow the beam and limit the amount of radiation which can impinge upon the photo diode. The signal from the photo diode is integrated by a signal processing unit so that the sensor can count a plurality of seeds in a group of seeds which simultaneously pass through the beam. The signal processing unit automatically compensates for changes in the steady state photo-diode output and for changes in seed size.