A Rotation Sensing Sensor

Not enough information.

Put a bump on the shaft and use a contact. Sorta like breaker point ignition on older cars.

A strip of white paint?

Not sure I understand entirely. How about this:

A narrow-beam red LED and a silicon sensor would form a transmitter/receiver pair. Aim the LED at the shaft. Any kind of mark on the shaft -- even a painted white dot -- would reflect a flash of red LED light that the sensor would see. If really high precision is needed a black label with a series of graduated white lines could be placed on the shaft to provide an instantaneous readout of rotational speed.

A Hall sensor is typically what is used.

Try THIS as a start. There are many others out there.

A plugging switch would be an easy way to do what you want.

http://www.geindustrial.com/cwc/Dispatcher?REQUEST=PRODUCTS&pnlid=3&famid=34&catid=108&id=plugsw

You may need to clarify the question. There are many methods for detecting rotation and measuring rotation that do not require a plc. A cheap microprocessor can do this sort of thing via many different types of input.

What do you want to do? Read an RPM? Detect rotation on or off? Does something need to respond to rotation? Would a simple tachometer work? What will "it" be "hard wired" to, and for what reason?

As usual the thread gets hi-jacked and over complicated. Good one MB for trying to get it back in line.

Have a look at http://www.redler.com/en/products/rocon/ I was using them 30 years ago. 2 wire relay switching. The sensor can be removed from the housing to give alternative mounting.

im using it as an interlock for a contactor. this sensor would see an auger shaft tur ning and allow the conveyor feeding the chipper to be on and if it is not seeing the shaft moving it doesnt allow the conveyor to be on. all this boils down to is sorry mechanical maint. not having the belts tight, not having the correct amount of belts on it and management throwing a hissy fit because they wont fire the "good old boys" and get real millwrights in the door and earn theyre pay check. sooo... i only know of encoders and prox wheels together w/ a plc watching for the rotatoinal pulse and thats not an option right now.

That's pretty easy, then.

USBport's idea would work fine. A microprocessor (such as a Basic stamp, etc: $20-50 or so) would simply look for a pulse, and then count time until the next pulse. If the time exceeds a reasonable value (depending on the speed range of the auger) the microprocessor energizes a relay which breaks the control circuit (NC contact opens) to the conveyor motor contactor.

Just guessing, but if one second goes by without another pulse, then the auger is stopped or close enough to stopped to indicate a problem.

You could build a robust housing for a simple led transmitter-receiver pair, use a magnet and a reed switch, micro switch and a bump, etc, etc. Depending on the application, the mechanical design (ensuring that the thing doesn't get knocked off, covered with dirt, etc.) will probably take longer than the electronics, which are essentially a no-brainer.

Even a 555 timer ($1.00?) could do this with very little supporting circuitry. The pulse would reset the timer (let's say to start a one second timing period). If the timer times out before another pulse arrives to reset it, a relay is actuated and latched.

You would want to be certain that the conveyor could not restart accidentally if the timer resets itself, etc. People could get hurt, potentially.

You don't need a PLC to monitor pulses. A simple retriggerable one shot timer module, circuit, whatever, can be used to detect loss of motion as you describe. Simply set the timer to be slightly longer than your pulse rate and when it arrives it re-triggers the timer. If it doesn't arrive, then the timer times out and closes a relay to some alarm.

Borrow the stuff from old equipment if you have to.

What you want to look for is a "Zero Speed Switch", they are VERY common for auger / screw conveyor applications, there are plenty of options out there. They are stand-alone devices for interlocking to motor starters etc., exactly as you plan to use it. Perhaps if you show some application examples to your bosses, they will recognize that this is a very common "best practice" for your kind of application and allow you to do it right.

Here is an example of a ZSS

There are many other manufacturers, check with your local suppliers. A lot of PT (Power Transmission) houses like Motion Industries, Applied Industrial Technologies or Kaman Industries will carry them if your electrical distributors do not.