Buffer circuit for stepper driver

[techdesk]

Hello all
I need help with a very simple circuit. I send pulse signals from a PLC to the stepper drivers STEP and DIR. I need a circuit to intercept these pulses and then send to the driver. the circuit must send the exact pulses once to the driver and after 500msec send the exact pulses but in the opposite, For Examplle if I send +1000 steps, the buffer must send this +1000 steps immediately to the driver and after 500msecs, resend the 1000 pulses but as -1000 steps.
Any help with a circuit here?
G Barnes

 

[ronsimpson]

I think the PLC can do that. Can you write PLC code?

 

[techdesk]

I can write GCode or I can upload GCode to the plc. I cannot find any GCode to do this function. The reason I want to use GCode is that many complicated drawings with arcs and circles can easily be converted into GCode from a DXF file.

 

[rjenkinsgb]

That does not sound like a PLC system? I've never seen a PLC used to directly interpret G code in a motion control system.

What is the actual controller in use?

 

[techdesk]

It is a standard offline PLC controller which uses GCode

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[rjenkinsgb]

OK, it is a "Motion controller".

What are you trying to achieve?
Moving the stepper other than via the motion controller will mean the controller no longer knows the axis position.

 

[rjenkinsgb]

You should be able to do it in G code.
eg. Switch to "relative positioning" with G91, give the move command to whatever axis controls that stepper output, dwell 0.5s using G04, then give the same move command in the opposite direction.

Something like, driving the Z axis:

N10 G00 G91 Z -1000
N20 G04 P500
N30 G00 Z1000
N40 G90 ; change back to normal "absolute" positioning, if needed.


Depending what you are trying to do & how critical the movement distance is, you may be able to do it with the G82 drilling cycle (drill with dwell) or a "peck drilling" cycle - G83, in the DDCS motion controller.