modicon plc / encoder

The first encoder programming experience.
A simple question that I think could be some answers but it´s difficult to decide the best.
How would you program an high frequency chart connect to an encoder to control a motor of vertical conveyor (up/down) with to speed, if the chart only have two outputs.
In abstract it is need three outputs (on for up, one for down and the other for high speed).
Possible answers:
- send a signal to the cpu to control the change of the speed with a normal binary output and use the two high freq. output to control up and down movement ?

I appreciate your concern

Thanks AMM

What's a "chart"?...

beerchug

-Eric

Good question.

The answers are in the details of the question AND information provided.

Is this a servo or stepper system?
Whats a high frequency chart?

NOTE: a conveyor is a conveyor..the position it is mounted doesnt have any bearing on WHAT it must do (except to relate to others). Technically a conveyor moves products/materials from point A to point B...more or less.

The answer to this is "it depends".
What kind of motor control is being used?
In many cases using AC, DC, servo or stepper its possible to use a communication protocol...ie DeviceNet, Profibus etc, These allow start, stop and speed cpntrol.

Depending on the system it may be possible to use the same output for UP?Down to also make the drive run at a PreSet speed.

I am just throwing things out for consideration.

Something tells me that Agostinho meant a high-speed counter card...

He is apparently trying to control the conveyor speed using the HSC card only, with its two outputs.

Sounds like a good guess Ladder...

You could use one output to switch from high speed to low speed when you approach position, then use the other to stop when you reach position. Forward/reverse (up/down?) should be selected by the PLC.

More details = better answers...

beerchug

-Eric

sorry, I really want to mean high-speed counter card, and not chart. It´s a AC motor controled by one frequency driver (380V in europe).
The question is about how can I get the best precision to the vertical conveyor that has 10 floor.
If I have only two outputs on the high-speed counter, I have to use them in the best way to assure the best performance in position. But on the other hand I need three signals to control the frequency driver.
By the way , it´s a modicon momentum plc (170 AEC 920 00)

Thanks

Agostinho:

The outputs on the high-speed counter card are not the only outputs you have. Normally, these outputs would be used if you want to do something really fast. For example, if you want to stop your conveyor at a certain position within 1-2 milliseconds or so. I don't think this would be required with the good old AC motor of yours.

However, the encoder position can be read from the HSC card into a PLC register (while this statement applies to all PLC brands, the actual implementation details would be brand-specific). This is usually a 32-bit number (DWORD, LONG or a similar type) and it will be updated every PLC scan, which is approximately 20 ms (once again, it may be somewhat lower or higher for different PLC types; it is also varies somewhat, but 20 ms is a good estimate).

So your PLC program will just read this value, compare it with the preset positions and energize or de-energize as many outputs as you have installed in your system. Of course you would have to fine-tune the presets, depending on the inertia of your system plus 20 ms latency... it is a trial and error thing. And of course it will not be an awfully accurate system: my guess is that you might be able to achieve stopping positions repeatable to approximately +/- 5 mm, maybe a little bit better.

If you need better accuracy and faster operation, you would have to upgrade to a servo/position control PLC module and to invest in a variable frequency drive (VFD)...

Agostinho

If you still have the problem post here, I use TSX Premuim to control an AC motor, with good results.

"This is a translation of the above sentence"

Se ainda não tiver resolvido o seu problema, ponha um post aqui. Eu tenho usado um TSX Premium para controlar um motor AC com bons resultados

João