Hi,
i use five PIR Motion sensors (used for switching lamps on, 230 Volt) in a very far distance and want to get their status into the Arduino (if they are on or off). My idea is, to connect 4,5 Volt Power Supplies with them (instead of 230 Volts-lights) and detect with the digital input pin of the arduino if they are on or off. So i want to connect the five power supplies into the digital input pins. My Question is: Is this possible, and if yes, do i need any resistors also, or do i have simply connect the +wire of the powersupply with an InputPin and the -wire of the powersupply with a groundpin of the arduino?
I think we need a bit more information.
Are you proposing to not have the lights at at all and put a 4.5v power supply in place of the light so that the sensor turns them on?
If so then yes you can detect this by feeding it directly into the digital input pin as long as you also connect the power supply ground to the arduino ground.
i want to do it the way as you suppose. i just want to know if a power supply is active or if not, and therefore i want to connect it with a digital input pin, while connecting its ground with arduino ground.
I had a similar project and used an AC optoisolator (with a capacitor and a couple of resistors) to connect to the Arduino inputs. I'm working on the PCB layout and will probably end up with a couple of different ones to shoehorn into existing electrical boxes on the equipment I'm sensing.