| 摘要 |
<p>An energy conserving circuit for controlling supply of electrical power to various loads such as a street lamp or a hot water heater comprises a photoelectric device for starting a timer when a change from daylight to dark is sensed at sundown, and a load power control responsive to the timer to switch between power-of and power-on states. With a street lamp the timer and power control means are connected to switch the power control means to power-on state at the beginning of the delay period at sundown and later, well before sunrise, to switch to power-off state. In the case of a household hot water heater the switching of the power control to power-on state is delayed until the peak demand hours have ended after sundown. The photoelectric device will normally cause the power control to switch to power-off state at sunrise. However, a second timer may be added which is responsive to the photoelectric device to start a second timing period ending after normal sunrise so that switching to power-off will occur if the photoelectric device does not or cannot respond to sunrise.</p> |
