1766 L32BWA Micrcontroller for super fast times?

Hello everyone

Some of you have probably been stumbling across a few questions i have asked recently, that is because i am doing my first project using a 1766 L32BWA microcontroller. The project has an HMI side to it and of course then there is the ladder logic side on RSLogix 500.

The project, in general terms, is detection of vent tubes using laser sensor, while a prox sensor is used along with this laser sensor to detect bolts. The laser sensor reading the vent tubes, and the prox reading the bolts (everything on the same rotating filler) are in sync. The bolts aren't going anywhere, so they can serve as a clock in order to skip the gaps that are between the vent tubes. So, if the prox is seeing a bolt then the laser sensor should be seeing a vent tube. But if the prox is not reading a bolt then the laser sensor is looking at the gap between the vent tubes. That being said, all the wiring is done, all the physical part of the project is complete. I see a bolt, i see the input on my controller. I see the vent tube with the laser sensor, i see the input on the microcontroller.

Our fillers can run upto 1600 cans a minute, and that is kind of fast for most processors with already bulked up programming. That is why i am using a separate microcontroller which will be dedicated to this one job! The thing is, when i start the filler at 300 cans per minute (so 300 vent tubes per minute going by the laser/ or 300 bolts per minute going by the prox) the inputs are just not keeping up with them. On the histogram, and even on the micrcontrollers display showing the inputs coming on and off, they are irregular and far apart. I can see the prox and laser sensor blinking at good intervals, constantly. But the controller is just not keeping up with it and i can't figure out if it is wiring issue or if i need to setup the controller to have faster scan times? Or do i need to use oneshots (Which i have not used before)?

Any and all input regarding this will be really helpful because i am at a point of the project where experience is the key to finishing, and i am very new at this. I have completed most of the stuff that required knowledge and reading manuals. I think there are itsy bitsy things that need to be tweaked in order to take this one home.

Again, i see all signals and everything when the filler is stationary.... but once it starts rotating, the inputs are just not coming on at the same rate, and dispersed over different lengths of time?

Is there a way to setup a project or routine or ladder file to be fast? Or to be a priority? Or something like that?

It might look something like this:

Your prox input is tied to a HSC. Set the HSC to trigger a dedicated program file at the count of 1. In that program file, check if the laser is on and set a bit or trigger an action. Reset the HSC at the end of that program file.

The laser input might not update fast enough for this if it’s not using another HSC. If the laser can be triggered before the bolt prox, you could potentially use another HSC for the laser input and the bolt triggered comparison might be if the laser HSC = 1 then reset both HSCs at the end of the comparison program file. If the bolt hits first, you could sense that the previous part was bad. If this doesn’t work, maybe each input could trigger a separate routine where the laser counts and the bolt compares. I haven’t done multiple HSCs myself so no guarantees.

This is provided the response times of all components are fast enough.

Get out the User Manual and read up on the Discrete Input Interrupt function. This sounds like an excellent application for those, as they can trigger a subroutine based on a very fast input pulse.

Also make sure you turn the input filters off. It's a pretty long filter by default.

But just FYI that processor is relatively slow by today's standards. A small program will have about a 3ms scan time, while that same program in a new 5069 CompactLogix would be about 0.1ms.