Compact Logix and Step/Direction

Big John T

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Nov 2006
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I have a compact logix plc and was told that they have function blocks to output step and direction pulses. All I can find seems to be related to motion control with an AB control card. The servo drive is panasonic as well as the servo and it takes step and direction signals. The servo takes 10,000 pulses per reveloution and can go 3000 rpm. That's 500,000 pulses a second... I was going to use a panasonic plc but my customer want's to use compact logix now...

Can anyone point me in the correct direction?

Thanks
John
 
First of all you have to find out how your servo drive is going to communicate with your plc.

All motion control instructions are designed on AB to be executed on AB motion control modules, that´s the reason I asked the question above.

The compact logic plc to handle motion control is the 1768-L43.
I do not think the panasonic PLC is capable to handle 500000 pulses per second.
 
After more research (I finally found the right manual) the pulse/direction input drive takes 2500 P/r and the encoder is 10,000 P/r feedback to the drive. This makes more sense than what the salesman told me...

The drive is rated at 3000 rpm with 2500 P/r. This gives me a max of 125,000 pulses/sec.

widelto, I assume that the drive only provides things like In Position, Busy, Alarm etc. back to the plc.

Thanks
John
 
If the drive can be setup to use an analog input for a velocity reference then if you step up to a ControlLogix and use a 1756-MO2AE (analog motion control module) you can use the RSLogix 5000 motion instructions. Otherwise, there is no available solution for what you looking for on the Logix platform that I am aware of.

Darren
 
widelto said:
First of all you have to find out how your servo drive is going to communicate with your plc.

All motion control instructions are designed on AB to be executed on AB motion control modules, that´s the reason I asked the question above.

The compact logic plc to handle motion control is the 1768-L43.
I do not think the panasonic PLC is capable to handle 500000 pulses per second.
Click to expand...

I did find out that the FPX has two 100kHz and two 20kHz outputs and that would give me 600 rpm as it does need the 10,000 pulses per reveloution.

The other late breaking news is it has electonic gearing so I can tell it to move 5 steps for each pulse so the 100kHz will get me the 3000 rpm max.


Thanks
John
 
I would look at the AMCI solution. It will go up to 1MHz on the pulse train and it will control velocity, position, accel/decel and profile (s-curve, trapazoidal, triangle) for a stepper.

This would work with any of the CompactLogix units since the loop is closed by the AMCI module. I would most likely look at the L35E, since it is the lower cost ethernet based processor. With compactlogix it is VERY important that you review the selection guide. There are some odd limitations with each processor and you MUST be aware of those issues before selecting one.
 
Last edited:
John:

There is an instruction called PTO ( pulse train ouput) this can only be used witl ML1200 or ML1500 from Allen Bradley, the maximum frequenci is 20Khz, this instruction is designed for a system like the one you want to implement. I ´m not sure but your encoder is connected to your drive not to the plc, so the plc is in charge of generating pulses a direction only. I remember having seen an apllication like yours in the AB web page, look for it, go to the knowledgebase.
 
Widelto, Thanks for the info. The panasonic will do 100kHz so it will do the job with the electronic gearing on the drive I can get 3000 rpm if I need it. They only wanted the CompactLogix because it is what they have a plant full of and it has ethernet...

Thanks
John
 

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