Problem with PTO

[Mabrill]

We have a problem with a PTO we use this to control a servomotor, in a bag maker machine, but when we use a sensor to stop it the PTO this take a little time to stop, then the machine stop few centimeters after the signal has been received. And when we increment the frecuency (speed) the distance of stop becomes higher. Somebody have any solution?

[Emil]

Hi,

The result you receive is normal. PLC checks the input at the beginning of the scan and operates PTO/HSO Run bit at the end. In this case you have reaction up to 2 controller's scans.

How you can improve the sitation?

You can connect the sensor to HSC Input and set this input as HSC Reload with target 0. Then, you need ot define an interrupt subroutine related to this HSC Reload. In this interrupt subroutine (see Help for details) you will Reset PTO/HSO Run bit and will set another one MB/XB.

You will divide your application to relativelly short subroutines. In your Main routine, before calling the next sub, you will perform a simple net - N.O. contact of the bit you set in interrupt sub - reset this bit and jump to End.

With this procedure, performed properly, you will decrease delay from two scan times (I guess about 5-15 ms) to less than 1 ms.

[Mabrill]

Hi Emil

I have used the tips that you tell me but the problem is the same i see a delay of 20ms. I have used the HSC interrupt and the immediate write to physical output but yet we have a delay so big. I use a V130-33-TR34.

How we can improve this?

[Emil]

Please attach your project. I want to take a look on it.

What is the PTO frequency when the signal from sensor comes?

What is the ration pulse/lenght?

Are you sure it's not a matter of mechanichal glitch?