Quote:
Originally Posted by Kevin Sevcik
That set up will pull the signal pin down to ~0.1V, which should be far enough for it to switch. Your sidecar wouldn't like you if you ever lost the lower leg while the sensor was on, but it should work.
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I agree. An opto-isolator is the correct way to do this interface. Using a resistor divider is a work around with some disadvantages. Inputs over 5 volts should be avoided on the DSC inputs. Hopefully, having a 350 ohm resistor in series with the 12 volt signal would limit the current enough to reduce the chance of damage even if the lower resistor came undone, But there is no guarantee.
Bottom line, use an opto-isolator if you can. Better yet, whenever possible use NPN output sensors that are active low so that they can connect directly to the DSC without any modifications.