Can proximity sensors be connected in series?
Yes. The number of proximity sensors connected in series is dependent on the available voltage to energize the PLC input or load. This voltage is calculated as the sum of voltage drops across each sensor subtracted from the available power supply voltage. Let’s use as an example three of the AutomationDirect APS24 series 3-wire NPN sensors, where the brown wire is positive, the black wire is the output, and the blue wire is the negative. The load will be a PLC input. By connecting the sensors in series, all of the sensors must be activated in order for the PLC to receive an input signal. Start by connecting the brown wire (BN+) of each sensor in a daisy chain configuration to the positive terminal (+) of a 24 VDC power supply. Next, connect one side of the load (PLC input module) to the first sensors’s brown wire (BN+) and the other side to the black wire (BK). Then connect that same sensor’s blue wire (BU-) to the second sensor’s black wire (BK). Connect the second sensor’s blue wire
