| 摘要 |
PURPOSE:To simply perform the adjustment of illuminance by selecting a sampling pulse width so that an oscillation frequency of a CR oscillator using a solar cell as a power source may fall within an error range according to the purpose of the use thereof. CONSTITUTION:When a light is applied to a solar cell 1, a voltage is impressed on a CR oscillator 2, and thereby oscillation is started. Next, when an outside switch Sw 1 is closed, an output of a NAND gate 8 turns to be at H level and a NAND gate 4 is released. Thereby an output frequency of the CR oscillator 2 is input to a counting circuit 5 via a level shifter 3 and the gate 4 and a frequency F is detected. When the counting circuit 5 is reset by a reset signal (r) to open switches Sw 1, 3 and 4 and close a switch Sw 2, the gate 4 is opened by a sampling signal E from a signal generating circuit 17, and thereby the frequency of the CR oscillator 2 is counted by the counting circuit 5. By selecting the sampling pulse width in the same way via the switches 2-4, the adjustment of illuminance is perfrmed simply. |
