Sensing my garage door

["Paul" <p-gale@xxxxxxx>]

One for the electronics experts:



In an attempt to remotely control and sense the condition of my garage
door, I've run several signals back from my garage door opener as
follows:



Two lines for the open/close operation - simple!

Three lines taken from the position micro switches - Gnd, +5V when open,
+5V when closed.



I'm trying to feed the microswitch signals into an opto-isolated simple
circuit and then into HomeVision so that I can tell when the door is
open/closed. The trouble is, I don't want to affect the garage door
opener in any way (and break it!).



I've currently got one of the gnd and +5V signals fed into the input of
the opto with a 1K resistor in series. Is this enough? How can I
maintain the +5V potential of the garage door circuit (and effectively
not effect it) but at the same time sense the voltage (very high value
resistor instead of the 1K???). Does that make sense?



If anyone can help (Frank?), I can sketch the setup if my explanation is
not clear.



TIA  :-)



Paul.





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