JPH0255971B

• Main Author: KATO TOSHUKI
• Format: Patent
• Language: English
• Published: 28.11.1990
• Subjects: ALARM SYSTEMS; ANALOGOUS ARRANGEMENTS USING OTHER WAVES; BASIC ELECTRONIC CIRCUITRY; CONTROL OF AMPLIFICATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; ELECTRICITY; EMBROIDERING; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION ORRERADIATION OF RADIO WAVES; MEASURING; ORDER TELEGRAPHS; PHYSICS; PULSE TECHNIQUE; RADIO DIRECTION-FINDING; RADIO NAVIGATION; SEWING; SIGNALLING; SIGNALLING OR CALLING SYSTEMS; TESTING; TEXTILES; TUFTING

PURPOSE:To prevent malfunction due to adhesion of dust, by generating a photodetecting signal kept constant at all times at an automatic gain adjusting circuit, determining a reference voltage based on the detecting signal and discriminating the photoreception and photointerruption. CONSTITUTION:In a cloth end detector for a sawing machine, a light is intermittently generated from a light emitting substance 3 at a constant period from an oscillator OSC. The reflected light of this light is received at a photodetector 4 and the photodetecting signal converted into an electric signal is inputted to an automatic gain adjusting circuit 16, where the input signal is received at a voltage controlled amplifier 5 to gradually decrease the amplification factor in synchronizing with the light emission of the body 3, and the output is converted to a constant voltage independently of the presence/absence of dust and outputted to a reference voltage storage circuit 17 and a comparison circuit 19. The circuit 17 decides a reference voltage based on the input voltage at the circuit 16 and outputs it to the circuit 19. The circuit 19 compares the two inputs, and when the output of the circuit 16 is an output or less of the circuit 17, a detection signal is generated and given to a CPU via a retrigger OS to a inform that an object to be detected is interposed between the light emitting body and the photodetector.