【正文】 3. (b) is A practical circuit, use A word of plastic wave along the steadystate produces single trigger word and b are pulse wave phase 39。s code has not actually had word of absolute encoder code, but produce counting pulse. It39。, D flipflop output waveform W1) for Q (low level, Q (W2) for high level waveform, the output crosscoupled nand gates close, high level (waveform W3), Now, two crosscoupled nand gates open, counting under impulsive through (waveform W4), send to twoway 74LS193 counter reduced input pulses, CD. Subtraction. Steering wheel clockwise and counterclockwise, the maximum rotation Angle for two laps, choose resolution for 360 pulse/circle of the output pulse coder, its biggest for 900, Actual use three slices of counts circuit 74LS193 ponent in the system of initialization, the signal reset (CLR), the initial set for 800H, namely 2048 (LD)。 can easily identify rotation direction, and for every turn A phase Z benchmark for positioning. Pulse, Its advantages are simple structure, mechanical principle, average life expectancy in tens of thousands of hours, strong antijamming capability, high reliability, suitable for long distance transmission. Its defect is not the absolute output shaft rotation location information. 圖 1 光電編碼器的遠離示意圖 Absolute photoelectric encoder Absolute encoder is direct digital output sensor, in its circular yards on several concentric yards along the radial direction of every faith, by pervious to light and not pervious to light, the sector and the adjacent code number of sectors, encoder is double the code number of bits of it in the code of digits, light source, the other side is one word has a corresponding yard photosensitive ponents, When the code in different position, the dish by various photosensitive ponents according to the corresponding conversion or light signals, binary 2 number level. This is not the encoder counter in the shaft can be read at any position of a fixed position corresponds with the digital code. Obviously, the word, the more the high resolution, for a N binary resolution coder code salver must have N barcode. Currently there are 16 bits of absolute encoder products. Single channel absolute photoelectric shaft encoder is using the natural binary or circular binary (Gregory yards) manner photoelectric conversion. Absolute photoelectric encoder and incremental encoder differs not pervious to light on the disk, the line, absolute encoders may have graphics, according to the number of code read code on coding, detection absolute position. Code design can use binary code, circulation, binary plement, etc. Its features are: Can read Angle of absolute coordinates directly. No accumulative error. Power excision location information would be lost. But the resolution is determined by the binary digits, ., precision depends on the median 10, 14 etc. Hybrid absolute encoder. Hybrid absolute encoders, its output of two groups: a group of information, information for testing poles with absolute information function, Another group of incremental encoder is pletely with the output information. Photoelectric encoder is an Angle (angular velocity) detection device, it will input shaft Angle for, using the principle of photoelectric convert electrical or digital accordingly, small size, high accuracy, high reliability, digital interface, etc. It is widely applied in nc machine tools, turning machine, servo drive, robots, radar and military targets were needed in the Angle of device and equipment. Applied circuit of photoelectric encoder EPC 755A application of photoelectric encoder EPC 755A photoelectric encoder and the use of good performance in Angle measurement, displacement measurement, and has strong antijamming capability of the output pulse signal is stable and reliable, and the pulse signal can be obtained by counting were measured after the digital signal. Therefore, we in the car driving simulators, steering wheel rotation Angle measurement chooses EPC 755A photoelectric encoder, the output circuit as sensors, choose open collector output resolution selection 360 pulse/circle, considering the steering wheel rotation is a twoway street, clockwise and counterclockwise, can also needs to the output signal phase coder to count. Figure 2 shows the actual use of photoelectric encoder and discrimination, phase twoway counts circuit with a D flipflop circuit and two crosscoupled nand gates, with 74LS193 3 counts circuit. 3 圖 2 光電編碼器鑒相計數(shù)電路 When the photoelectric encoder clockwise, channel, A le