| 摘要 |
<p>PURPOSE:To eliminate the need to adjust the sensitivity of a sensor for each product with a variable resistor and to cope with a shift in the mechanical fitting position of the sensor by controlling the quantity of light of a light emission part so that a photodetection part operates in an unsaturated area. CONSTITUTION:A reference voltage Vref1 for detecting whether or not a voltage exceeds a collector saturation voltage Vce(sat) is set as the threshold voltage of a comparator 8 in addition to normal Vref2, and they are switched by a CPU 13. A LED current is set to If1 and the threshold voltage is set to the Vref1. Then when the output voltage Eout of a phototransistor (Tr) 1b is smaller than the voltage Vref1, the Tr 1b is not saturated, so the LED current is set to If1 and information on that is stored in a nonvolatile RAM 14. When voltage Eout>=Vref1, on the other hand, the LED current is switched to If2 and information on that is stored in the RAM 14. Then when the system is powered on, the values of the RAM 14 are outputted to an output port 11 and the CPU 13 operates the photosensor 1 while grasping variation of the element.</p> |
