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Article: Tachometer circuit reduces parts count. (Design Ideas) (technical)
- Article from:
- EDN
- Article date:
- February 16, 1989
- Author:
CopyrightCOPYRIGHT 1989 Reed Business Information, Inc. (US). This material is published under license from the publisher through the Gale Group, Farmington Hills, Michigan. All inquiries regarding rights should be directed to the Gale Group. (Hide copyright information)
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Tachometer circuit reduces parts count The tachometer circuit of Fig 1 requires only one IC (besides the counter), yet it achieves the same resolution and eliminates backlash just as the 3-IC circuit of an earlier Design Idea did ("Improved tachometer eliminates backlash," March 31, 1987, pg 210).
A standard shaft encoder's A and B ports generate square waves with the same frequency as the shaft turns. The phase of A will lead or lag that of B by 90[deg.], depending on the direction of rotation. To obtain maximum resolution, the tachometer circuit must count every change of state for the A and B signals. Each such change causes a change of state at IC.sub.1A.'s ...