| 摘要 |
PURPOSE:To facilitate an easy control of an external device using a personal computer, etc., by using a relay switch which opens and closes with the luminance variations on the screen of a personal computer, etc. CONSTITUTION:A photoconductive cell CdS1 which is enclosed by a sucking disk 7 and detects the variation of luminance is adhered at a proper position, e.g., the upper right corner of a screen 11 of a personal computer, etc. This CdS1 is connected in series to a variable resistor 6 for control of sensitivity at a point A. The output of the point A is made pass through a Schmitt circuit 2 consisting of two inverters to deliver assuredly a signal 1 or 0. This output is supplied to the base of a transistor TR3 to turn on and off the TR3, and a relay 4 is opened and closed with a collector current to switch on and off the power supply of a load 5 (a TV for instance). The luminance of a display part rises up or drops down at a desired time point by making use of the timepiece function of the personal computer. In such a way, a control function of an external device can be simply provided to a personal computer. |
