Programmable Devices Implement Highly Accurate Optical Tachometer
by Bilal Ahmed, Silego Technology, Santa Clara, Calif., How2Power Today, Apr 17 2017
Focus:
Hall Effect sensors are commonly used in tachometers, which measure the speed of a
rotating object in RPM. While these tachometers are highly accurate over most of their
operating range they are known to give false readings at low speeds. That’s because at low
speeds the vibration of the motor/rotational objects causes the magnetics-based Hall
sensor to behave erratically. This article describes an optical contactless tachometer
that achieves better accuracy at all speeds through the use of an infrared LED sensor. The
design described here is based on three GreenPAK SLG46533V ICs, which are programmable
mixed-signal matrix chips integrating a variety of functions. The sensor portion of the
tachometer consists of an infrared transmitter LED and receiver LED, which works with an
SLG46533V to detect the reflected (incoming) infrared rays. A small cooling fan is used to
demonstrate this tachometer. The design can also be used with a rotary encoder.
What you’ll learn:
- How to design an infrared sensor-based tachometer that provides high accuracy across the full speed range
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