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f,FU.qgi!W* From datasheet:
Circuits lor Input lrom a Hall eflecl
sensor inlo a PlC, ([,{elexis N|LX9021 7.)

we will be using the input from a two-channel optical encoder attached to a small dc
motor as our signal source. This encoder has 20 slots around its periphery so we will
get 20 pulses per revolution. We will look atjust one channel because we are interested
oniy in the signal frequency.
The circuitry for the LED pholotransistor pair for the one channel in this delector is
as shown in Figure 15.6.

5 VOLTS

slgnalis HIGH whsn
the lR LED is oN and

Circuils for the inpui of a tachometer
signal into a PIC from the motor optics.