Help needed with proximity switches

[Robin Hewitt]

An NPN sensor means the output is an NPN transistor which is wired as a switch to ground, if it was a PNP it would be a switch to the voltage rail.
So what you have is a resistor pull up which will show volts until you turn on the NPN when it will show ground.
But you don't want volts, you want current so you have to add resistors to get the current down to something that doesn't blow the LED in the BOB.
Ohms law sez R=V/I
V is the voltage guess 24V less 1.5V for the LED, 22.5 V
I is the Amps, guess 15mA for the LED, 0.015 A
R = 22.5/0.015 = 1500R = 1k5
10k sounds like way too much.
Where's Irving when you need him?