When designing a system where a decision is being made by that system’s controller for an action to be taken further down the line, you have two methods to choose from for that controller to make the action happen. One is time-based the other is encoder-based.
The time-based option operates very simply. Let’s say that a product is being weighed in motion to determine a certain line that the product should be sent down. Once the products weight has been established by the controller and the appropriate location has been determined, the controller will have been programmed to know that the line is a certain amount of time away, so it will begin counting down, and when that countdown ends, a divert will be activated to send that product down that line.
This is a very simple and effective system as long as nothing ever changes, like line speed. If the line speed is sped up, the product would be past the proper divert before it was activated, and if the line was shut off even for a brief amount of time, all of the timing could be thrown off.
To safeguard against this, we like to use an encoder-based system. To explain what an encoder is, basically, the system’s controller will count how many times the shaft on the conveyor turns. Now every system is different but let’s just say that, with this system, every time the shaft turns one time, the conveyor belt will travel six inches. So, with this encoder-based system the controller will have been programmed to know that the divert is a certain number of shaft revolutions away, and all it has to do is count these revolutions and then activate that divert. With this system, speeding things up, slowing things down, or even stopping the system will not affect the process.
That was a very basic description of an encoder. Encoder technology is actually much more advanced than that. In the previously mentioned system, the encoder would send one electrical signal to the system controller for every revolution of the shaft signaling six inches of travel. If this encoder were to send two electrical signals for every shaft revolution, the system’s controller would know that every electrical signal from the encoder would be equal to three inches of travel. Four electrical signals from the encoder would mean each signal would equal one and a half inches of travel.
Encoders are available that can send over one thousand electrical signals for each revolution of the shaft. This can allow for very accurate tracking of anything on a conveyor.