The LJ12A3-4-Z/BX sensors I use with this board are NPN - the output of the sensor goes to GND when triggered - which is what you want. The board has pull-up resistors so that the untriggered state is strapped to 5v. You don't need resistors as the 24v power to the sensor is limited in current to 2.4mA and in voltage by an internal zener diode in the switching circuit.
Originally Posted by paulus.v
These sensors have been designed to make connection simple and to have wide application, why do people then have to make things complicated. If you complicate you introduce the possibility of design faults and unreliability.
I lose the will to live every time someone mentions a relay in a homes circuit.
For Pete's sake, there is plenty of info and advice on t'Interweb. Do a bit of searching online before you regurgitate the same old questions.
Happy bloody christmas !!!!
It takes all sorts to make a world, I am just glad I am not one of them.