Jet looms encoder working principle and general troubleshooting methods ！

Jet looms encoder working principle and general troubleshooting methods

1 Encoder working principle


        Optical encoders are commonly used angular displacement detection element is detected as an electrical control unit on the basis of various timing signals necessary for each crank angle of 2 degrees in the output of the air-jet looms. Belgium than Jiale loom factory (PICANOL) produced PAT-A-jet loom encoder uses a binary code disc. Because of 0-358 degrees every 2 degrees a total of 180 digital output, you need 8-bit binary code disc, the disc is divided into 180 equal parts, and is divided into 8 rings, each ring corresponds to the encoded bits, called code channel , constituted by the permutations and angular position of transparent and opaque black and white areas corresponding to digital.


        Corresponding to the code wheel each code channel, there is a photodetector diode, when the code wheel at different angles, the digital signal to the transparent and opaque regions consisting of photodiodes or not the light is converted into an electrical signal to the CPU plate angular displacement values ​​can be obtained.


        Light emitting diode + 18V power supply is provided by the power supply board SMPSS, light-diode power obtained from the + 5V + 18V after LM317 by two external resistors transformation. LM339 comparator negative input terminal by + 5V via a resistor after the partial pressure of supplied + 3V reference voltage when the emitter photocell light-that is, the comparator outputs a high voltage when obscured from the light, the comparator output low, eight high and low by the driver input to the CPU board, so as to obtain the angular displacement value.


        2 Maintenance Examples


        2.1 pass into the + 18V power supply, the hand rotating encoder disk with one output is always low, this route comparator LM339 (14 feet) output control, the amount was 14 foot jump while rotating encoder disk between the high and low change. Disconnect the power, volume was LM339 (14) feet and drive Manifold UDN2983A corresponding gate between nowhere, with a wire connecting the feet up after troubleshooting, the encoder resume normal use.


        2.2 pass into the + 18V power supply, turn the encoder disk, there is no way to output, the amount was no way corresponds to the comparator output. The amount with a multimeter voltage profile was more negative terminal of the reference voltage + 3V input and a positive input terminal at hand rotating encoder disk between 2.5V and 0V changes only, so no comparator output. The test signal input resistance resistance for a slightly larger resistance, troubleshooting (encoder circuit board resistance chip resistors, instead of an ordinary resistor).


        2.3 pass into the + 18V power supply, turn the encoder disk, eight can change between high and low, while the machine is displayed on the machine Shique inversion phenomenon, replace the encoder after-hours troubleshooting.


        3 Summary


        When PAT jet loom encoder is damaged, such as the purchase of imported undisturbed encoder on the yuan each required funds, to save costs, to try to repair the repair. First, use a multimeter to check whether there is a fault output line is broken, then ethanol for each part of the encoder to do a thorough cleaning, which leads to + 18V supply, the hand rotating encoder disk, measured with a multimeter eight output terminal voltage, should changes between the high (+ 15V or so) and low (0V) in, what if the road can not change, there is a fault, identify the input output signal points, check if there are broken, Weld and resistance value changes and other phenomena. Encoder element little damage, if the encoder disk is good, this method can generally be repaired.

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