Photoelectric encoder！

Photoelectric encoder used with good performance, the angle measurement, displacement measurement of anti-interference ability is very strong, and has a stable and reliable output pulse signal and the pulse signal by the digital signal is obtained after counting taped. Therefore, we in the development of automobile driving simulator, steering wheel rotation angle measurement selection of EPC-755A optical encoder as a sensor, the output circuit used open collector type, choose the output resolution of 360 pulses / revolution, taking into account the steering wheel rotation in both directions, clockwise rotation can also be rotated counterclockwise, the need for an output signal of the encoder after phase can count. Figure 2 shows bi-phase discriminator counting circuit photoelectric encoder actual use phase circuits and a D flip-flop consisting of two NAND gates, counter circuit with three 74LS193 composition.

When the optical encoder clockwise channel A leads channel B output waveform of the output waveform of 90 °, D flip-flop output Q (waveform W1) is high, Q (waveform W2) is low, the above NAND gate open , by counting pulses (W3 of the waveform), the counter is incremented to the bidirectional pulse input terminal of the CU 74LS193, counts up; in this case, following the NAND gate closed, its output is high (waveform W4). When the counter-clockwise optical encoder, channel A Channel B output waveform of the output waveform delay than 90 °, D flip-flop output Q (waveform W1) is low, Q (waveform W2) is high above the NAND gate closed, its output is high (W3 of the waveform); in this case, the following NAND gate opening, by counting pulses (W4 of the waveform), the counter is decremented to the bidirectional pulse input terminal of the CD 74LS193, subtraction count.

When the steering wheel clockwise and counterclockwise rotation, the maximum rotation angles are twice and a half, use a resolution of 360 pulses / turn encoders, the maximum number of output pulses is 900; the actual use of the counting circuit with three 74LS193 composition, power initialized on system, the first of its reset (CLR signal), then its initial value is set to 800H, ie 2048 (LD signal); so, when the steering wheel is rotated clockwise, counter circuit output range 2048 ~ 2948, when the steering wheel is rotated counter-clockwise, counter circuit output in the range of 2048 - 1148; data counting circuit output D0 ~ D11 to the data processing circuit.

Actual use, the steering wheel is rotated counterclockwise and frequent clockwise, due to quantization error, after a long period of work, when the steering wheel back in the counter circuit 2048 may not be output, but the deviation of words; to solve a problem, we added a steering wheel back in the detection circuit, the system works, the data processing circuit in a simulator in the non-operated state, the system detects gyrus detecting circuit, if the steering wheel is back in the state, but not the count data output circuit 2048, counting circuit can be reset and re-set the initial value.

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