proximity sensor

Hi All, It's been a long time since the high school electronics classes doing circuit design. I have a CNC router and need to connect up 2 Proximity Sensors to the one GPIO input. I have tried connecting them in series, but I am only getting a 12V trigger signal with 24V supply. So I thought...

Hi, I have a project that i would like to complete. i need to activate an LED light outdoors, whenever a designated vehicle comes within 200-300metres of the LED light. i was thinking of using a simple 12v FM radio transmitter on the vehicle. the LED would have an FM radio reciever tuned to...

Hi, can anyone help me with ideas on building devices that produce an audible signal when come close to each other, say 2 meters or less. Both devices continue signalling until they are two or more meters apart. Think about a microphone moved close to a speaker - you hear an unpleasant...