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How can we detect the direction of disc rotation?！
Changchun Rongde Optics Co.,Ltd. Release time：2016/8/11 Browse：1078This solution with only a sensing head is not able to identify the direction of disc rotation. To solve this problem another optical sensing head is used, with its output signal offset from the first by 90°; in other words, the optical sensor sensing head signals are in quadrature. This layout produces two square waves in quadrature, corresponding each to one sensing head (channels A and B), as shown in Figure 4.
Therefore, the direction can be detected by the sequence in which arise the pairs of logical values 0 and 1. That is, if after 01 is received 11, this means moving to the right, while receiving 00 will mean moving to the left.
However, this is not the only advantage available, as can be perceived from the sequence of binary pairs separated by the green lines in Figure 4. With only one optical sensing head, there is only one impulse per period, but with two optical heads, a period will correspond to four pulses. Figure 4 shows the output of the two associated channels (A and B), and helps to understand the emergence of the four pulses per period of one channel (A or B), with the logical levels formed from combining the two waves. With each change of state from 00 to 01, etc., the new combination gives rise to another step in the counting operation. Consequently
the resolution is increased 4 times, as given by: 360º / (9 x 4) = 10
the resolution is increased 4 times, as given by: 360º / (9 x 4) = 10
incremental encoder,absolute encoder,rotary encoder
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