Book Analog Interfacing to Embedded Microprocessors
A common use for optical
isolators is to isolate a high-voltage circuit from the microprocessor that con-
trols it. MIDI (Musical Instrument Digital Interface) uses optical isolation to
connect synthesizers, computers, and other electronic musical instruments.
In this application, the use of optical isolators prevents problems caused by
different ground potentials.
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Figure 3.12
Optoisolator.
Figure 3.12 shows how an optoisolator can be used to pass signals from
one system to another. The ground and power connections for the system
may be completely separate. Even in a single system where the grounds
are nominally the same, an optoisolator may be used to prevent current
from flowing from one ground to the other. If one ground is particularly
noisy, such as the ground for a PWM (pulse-width modulated) motor
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