help using a bit shift left or right

I have an application where I need to detect a bad product on a conveyor, and then reject the bad product off of the conveyor. The conveyor does change speeds,and there will be a different number of this product on the conveyor at differnt times. Is using a bit shift left or right the way to do this, and if yes how would you program this application. I'll be using a AB slc-500, with rs-logic program.

Does conveyor only change speed or both speed and direction? What is the conveyor speed? What is the rate of products moving on convoeyor?

Since you need to "Quality-TAG" a product (0-1) and then you need to act on it along the line, you should be using a FIFO.

No Problem.....

Yes, you can use a BSL to easily pick out your reject product. You need to shift using a pulse generator prox or encoder, and you need to drop a bit in when you determine the part is defective. Lastly you need to find the reject position in your file you will use to active the reject process. If your conveyor is reversing, you need to BSR while the conveyor moves backward. Conveyor speed is not an issue with this method.

conveyor

Panic Mode,
The conveyor only slows down it never changes direction. The conveyor speed is only about 40 rpm measuring from driven shaft.

As Vette said speed is not really relevant. What is relevant is detecting the bad product AND counting the product at same time. You will need to use a device that allows you to determine count and position when a bad product is detected you will know which to reject.

Simple example: A word uses 16 bits so we count up to 16. This word is all zeroes until a bad product is detected then a 1 gets placed in the word address, each time a good bottle comes thru that 1 shifts (FIFO, BSL, BSR all depends). There are a variety of ways to do this but to keep it simple we have one bad product and good products are entering until the "1" for the bad product is at a certain point...which triggers the reject. Lets say we have 16 bottles, the first one is bad, the good come in and the bit shifts till its at the 16th position...the plc seeing a "1" in the 16th position triggers the reject.

There are examples of this on this site and others but if you take the time to figure it out yourself you will benefit alot more.

I use the BSL or BSR instruction for following steel bars through a high
speed processing machine. Utilizing an
encoder & HSCE2 module the ends of the
material can be tracked thru the entire
machine. Each bit can represent inches or
millimeters. At predefined points
in the shift register many functions
can be activated such as load bar ,
clamp bar , good bar eject , bad bar
eject, etc. ( b3/52=52 inches from sensorpoint/reject input ) As mentioned it
does not matter how fast the line is going.
Our line runs bar after bar up to 150
f.p.m. with excellant repeatability.