402-00005-00
Using Opto-Isolators
B–2
Rev 02; February 8, 2002
Input Circuits
2.2 K ohm
+ input
– input
Value
Internal to PCVisionplus
Vcc or PWR
or
trigger
Figure B–2. Opto-Coupled Input Circuit
Figure B–2 shows the internal circuitry in the opto-coupled input. When the diode is excited, the transistor is on, and
the internal Value is zero. When the diode is off, the transistor is off, and the internal Value is one. This circuit is used
on the otpot-coupled trigger inputs.
Figure B–3 shows a few examples for using the input. The positive input is connected to your logic or signal, and the
negative input is connected to ground through a resistor (330 ohm 1/8 Watt shown). The resistor limits current
through the diode. The external resistor (1 K ohm shown) limits the voltage across the diode. When the external input
goes high the diode turns on, and the internal Value (input) becomes zero. When the external input goes low the diode
turns off, and the internal Value becomes one. The diode and resistors are the Load connected to a sensor output.
The component values depend upon the voltage and current of your circuits. Do not exceed the Absolute Maxi-
mum Ratings of the input diode (page NO TAG).
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