Help pls

Hi I'm new to the forum and here is my question.I need to detect the direction and speed of a motor by using a PLC. So can anyone help me ?

What type of motor is it.

It if is a reversing motor, than the logic determines the direction.

It it is a variable speed motor, than you should be able to take a contact from the drive or again the logic.

If the motor is fitted with a quadrature encoder and the PLC has a high speed counter function, it's easy.

If none of the above applies or is appealing to you, you can also place 2 proximity sensors near an accessible motor shaft and look for a key (or keyway) passing by. Place the switches 45 degrees from each other and watch for which one represents the leading edge to determine rotation direction, then feed pulse counts from one or both into a counter and compare to a time base to calculate speed.

I agree with Jraef but you can do it simpler.

Use the two sensors and a key that can be detected by both detector at same time. If they have 45º the key must have a litle bit more. To know the rotation direction you test which sensor is detected first. Anyway you allways need fast inputs and you can make it like if you have an AB encoder with one pulse per rotation.