| 摘要 |
PURPOSE:To detect the disconnection in any case at the time of operation and at the time of stop by providing two light emitting elements for emitting a light beam alternately by pulse signals of two phases which are inverted, and a light receiving element for photodetecting the light beam of these light emitting elements. CONSTITUTION:Between an encoder and a counter circuit, an interface circuit 6 is provided and they are isolated. In a disconnection detecting device D, LEDs 7, 8 are connected in parallel to an input side, and emit a light beam when pulse signals of an A phase and an inverted A phase are H, respectively. The LEDs 7, 8 use an element whose delay time is comparatively long. A phototransistor 9 is connected to an output side, and photodetects a light beam of the LEDs 7, 8. When there is no disconnection in a signal line from the encoder, the LEDs 7, 8 emit a light beam alternately and continuously, and a disconnection signal Xa outputted from a transistor 9 is L. In the case a disconnection is generated in the signal line, the pulse signals of an A phase and an inverted A phase both become L at the time when the disconnection is generated. Accordingly, the LEDs 7, 8 come not to emit a light beam, the disconnection signal Xa becomes H at an interval of a time lag, and the generation of disconnection is informed to an emergency stop circuit. |
