1Principle and application of the photoelectric encoder circuitAccording to the test principle, encoder can be divided into optical type, magnet, inductive and capacitive. According to its calibration method and signal output form, can be divided into incremental, absolute type and hybrid 3 kinds.Incremental encoder is directly for the use of photoelectric conversion principle output three square wave pulsed A, B and Z phase; A, B two groups of pulse phase difference 90 DHS, thus can easily tell direction of rotation, and Z for every turn in a pulse, used to benchmark positioning. Its advantages are simple structure, mechanical principle of average life expectancy in the tens of thousands of hours above can be, strong anti-jamming capability, high reliability, suitable for long distance transmission. Its defect is unable to output shaft rotation absolute location information.Absolute encoder is direct output digital quantity sensor, in its circular yards plate along radial direction several concentric yards way, each of which way the by pervious to light and opaque and sector of the sector, adjacent code word number is double relationship, yards dish the code word is its binary number of digits, digital side in the code salver illuminant, another side corresponding to every one yard way have a photosensitive component; When yards in different position, disk by various photosensitive components according to the corresponding light or not conversion, forming a binary number level signal. The characteristics of the encoder counter and axis is not in any position can be read out a fixed position and corresponding digital yards. Obviously, code word, the more the better the resolution, for an N binary resolution coder code salver must have N barcode way. For an N binary resolution coder code salver must have N barcode way. At present domestic have 16 bits of absolute encoders products.Absolute photoelectric encoder is use natural binary or circulation binary (Gregory yards) manner photoelectric conversion. Absolute photoelectric encoder and incremental encoder difference in disk pervious to light, opaque line graph, absolute encoder can have some code, according to read yards plate coding, detection absolute position. Code design can use binary code, recycling yards, binary fill yards, etc. Its features are:(1) can directly read Angle coordinate of the absolute value;(2) have no cumulative error;(3) power excision location information would be lost. But the resolution is 2decided by the binary digits, i.e. precision, currently depends on digits 10, 14 and so on many kinds.Hybrid absolute encoders, it outputs two group of information: a group of information used to test with absolute poles position, information function; Then another group the same output information incremental encoder.Photoelectric encoder is an Angle (angular velocity) detection device, it will input shaft Angle to using photoelectric conversion principle amount converted into electrical impulses or digital quantity, with small size, high accuracy, high reliability, etc. The interface digital It is widely used in nc machine tools, rotating table, servo drive, robots, radar and military goals determination, need to detect the device and equipment in perspective.EPC - 755A photoelectric encoder is good performance in Angle measurement, displacement measurement anti-interference ability strong and stable and reliable, and the output pulse signal, and the pulse signal can be obtained by counting is measured after digital signal. Therefore, we are developing automobile driving simulator, the steering wheel rotation Angle measurement choose EPC - 755A photoelectric encoder, the output circuit as the sensor type selection, open collector output resolution choose 360 pulse/circle, considering the steering wheel rotation is bidirectional, both clockwise and counterclockwise, also can output signal encoder to phase discrimination to count.When photoelectric encoder clockwise, channel A output waveforms output waveform advance channel B, D flip-flop 90 output Q (waveform W1) high level, Q (waveform W2) for low level, top and open, counting pulse sr W3) by (waveform, send to the 74LS193 two-way counter with pulse, input CU addition count; At this time, with closed, its below sr output high level (waveform W4). When photoelectric encoder when A counterclockwise, channel output waveform of output waveform than channel B, D flip-flop 90 delay output Q (waveform W1) for low level, Q (waveform W2) high level, top and shut, its output sr for high level (waveform W3); At this time, with open, count below sr W4) by (pulse waveform, send to two-way counter reduced input pulses 74LS193, subtraction count CD.Steering wheel clockwise and counter-clockwise, the maximum rotation Angle are two laps half, choose resolution for the 360 pulse/laps of coder maximum output pulse count for 900; The actual use of three slices o