Automatic control for an adjustable member

摘要

A switching arrangement for the control of an adjustable member such as a valve includes a light sensitive switch. Detection of a particular light value enables a frequency divider to transmit an opening pulse to a valve control circuit a predetermined delay period after the detection of such light value. The frequency of an output signal of a pulse generator is varied in response to the opening pulse and the frequency divider transmits a closing pulse to the control circuit after a second predetermined time period of different duration from the delay period. In one disclosed embodiment, control of the frequency divider is responsive to moisture content of soil as well as ambient light level for application in automatic sprinkler systems.