S7-1200 PTO

Previously I used the S7-200 and used the inbuilt PTO outputs. I had direct access to these using the SM memory area.

Having moved to the S7-1200, it seem the only way to use the PTO outputs if the Motion Control function blocks.

I use the pulse train to control a motor that only accepts a pulse train, the problem I have is I need quick response from the motor, therefore also the pulse train.

Is there a way to manually run the PTO when needed? I have tried the JOG function, but it doesn't start and stop quick enough, as in the response from the ladder to the output turning off is variable.

The PLC is running a labeller, so when I see the label sensor, I need to turn off the pulse accurately. The label sensor is on a hardware interrupt. I know this doesn't fall in the category of positioning/motion control, but I really need to be able to control the pulse more manually

Many thanks,

Paul L

Previously I used the S7-200 and used the inbuilt PTO outputs. I had direct access to these using the SM memory area.

Having moved to the S7-1200, it seem the only way to use the PTO outputs if the Motion Control function blocks.

I use the pulse train to control a motor that only accepts a pulse train, the problem I have is I need quick response from the motor, therefore also the pulse train.

Is there a way to manually run the PTO when needed? I have tried the JOG function, but it doesn't start and stop quick enough, as in the response from the ladder to the output turning off is variable.

The PLC is running a labeller, so when I see the label sensor, I need to turn off the pulse accurately. The label sensor is on a hardware interrupt. I know this doesn't fall in the category of positioning/motion control, but I really need to be able to control the pulse more manually

Many thanks,

( I miss the S7-200 !! )

The motion control is the only way to generate a variable frequency pulse. If you need a fixed frequency pulse, then rather use PWM at a fixed frequency and set at 50% duty.

Try shortening the acceleration / deceleration rate or increasing the start-stop speed. Alternatively investigate the immediate stop available on MC_POWER.

Beware - the motion control has a scan update of 10ms. You may find that this will hinder you.

Good luck.
w

Thanks for the reply!

I need to alter the frequency, so the PWM won't do, I was just looking into that actually.

The 10ms is the killer. The labeller is going quite fast, up to 60mpm, so 1ms = 1mm. That's a lot of error.

The immediate stop is worth trying, but I also need to start accurately.

It seems the S7-1200 will be struggling to achieve what I want. The S7-200 seemed to work fine doing this!

Fort2535

Hi!

You achieve perform control label? I am you doing something similar, you will have an example of your control?

Look at this web page [LINK].
Several links are also given, which includes [LINK].

In short you will need to set up a motion control function to control the PTO of the PLC.
As Paul L suggests - the start and stop should be accurate.
I cannot promise you those two attributes on the S7-1200.
..but we'll leave this open for debate by others.

w