| 摘要 |
PURPOSE:To decrease the number of parts, to reduce the cost and to realize its minimization by changing light emission conditions of two light emitting diodes by turning on/off of one transistor. CONSTITUTION:A negative signal is given to the base of a transistor 4 at the regular rotation, and the signal is turned off. The current does not run to a light emitting diode 5, and an optical sensor on the opposite side does not operate. At this time, the current runs to a light emitting diode 2 through a diode 9, a phototransistor 3 is turned on/off by a reflection plate 7 which interlocks with a take-up reel, and a pulse for rotational detection is outputted. At the time of inversion, a positive signal is impressed on the base of the transistor 4 so that the signal will saturate a voltage VCE between a collector and an emitter. Thus, the transistor 4 conducts, the emitting diode 5 lights up, and a phototransistor 6 turns on/off by a reflection plate 8 which interlocks with the take-up reel at the time of inversion. Then, the rotational detection pulse is outputted. Thus, two optical sensors can be changed easily by the control signal to one switching transistor.
|
