Reply to "Using an optocoupler to connect insulated rail to input pin of shift register"

gunrunnerjohnOGR Forum Member SUPPORTING MEMBERDIGITAL SUBSCRIBER

Randy P. posted:
When using the shift registers to monitor inputs going to ground, such as pushbuttons and relay contact closures (typically with a pull-up resistor), I don't think current sink/source limitations are a factor - at least not as I have been using them.

It appears that they have a similar limitation on VSS, 150 ma maximum into the pin. Any pull-down is going to have to go through the VSS pin and would be subject to the 150ma limitation.

4/3/174:35 PM

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