Keyence PLC High Speed Counter

[DKahmer]

I'm trying to figure out if I'm doing this correctly or not and was hoping you guys could help a noob out!

I have a motor spinning a large gear, turning a cam. The cam is set so that I have 4 cam "pulses" with every one gear rotation. I have a small magnet on the gear, and a proximity sensor picking it up as an input to my PLC. I need to be able to have 20 cam rotations (5 gear rotations) per second. They advertise at the scan time being 140 us. So should be more than capable of that with just a standard input and counter correct?

I was counting along as I watched it spin but the counter I was monitor was not registering at the same pace. Do you think my the signal just wasn't strong enough from the prox sensor to register the input?

 

[OkiePC]

To find out if the pulses can be read consistently, you need to know the on dwell time and off dwell time of the pulses. Both of these durations need to be longer than your maximum actual (not advertised) scan time for optimal results. In most cases, you won't be getting a symmetrical square wave, so you need to focus on the shortest on and off times that you're actually generating.

I don't have any Keyence PLC experience but hopefully there is a way to monitor actual scan time.

Also, you need to research the specifications for the input points. Make sure there is no electronic filtering, or if there is, that it is configured to be fast enough for your pulses including any specified turn on/turn off delays for the input type.

 

[DKahmer]

I decided on just using a highspeed counter. There really was no reason for me not to try it that way. It's working fine now, thanks though!