Motor Control program

[alhernandez]

Hi!

Can any one help me out on this?

I am new to this thing, and I am trying to make a positioning system that has a lead screw whit a 5mm linear motion per rev., move by a 24dc gear motor of either a 725rpm or 215rpm (have not decided yet which one to use?) and a 1000 count encoder
It needs to be move 200mm per section and I been thinking in using an AB Pico controller.
The way I see things is to use the encoder to do 4000 count when the motor is running, stop the motor at 4000 counts punch a hole and move another 4000 counts, punch and so on for 25 section. Overall it will move 500mm.
The question is HOW CAN I CONNECT THE ENCODER TO THE PLC AND WHICH MOTOR WOULD BE THE BEST TO USE? The ladder program I have a fair idea, but if any one can help on this I would appreciated.
The motor, lead screw, the encoder I have but I am not sure about the PLC.

Thank You in advance to any one that replies

 

[seppoalanen]

I don't know Pico, is it possible use DeviceNet. Absolute-encoder in DeviceNet is good solution becourse it knows position while there is no Voltage or someone turn it manually without motor.
Inputs via D-Net tells directly the position without any impulse calculation. Usually position data tells how many rounds 12-13 bits and 12 bits for one round, all binary coded. Preset via D-Net fe. 0 or what ever, is possible and count-direction selection in start-up.
What motor ? Is VFD and normal 3-phase motor impposible ?

 

[rsdoran]

Seems you will need precision, is that correct?

The PICO is nothing more than a programmable relay/timer/counter, its max frequency is somewhere around 100hz. I dont think that will work well for your application.

What I see from your descripiton is a need for precision...ie the machine needs to move 20mm then punch and move again 20mm then punch until 25 punches have been made, which would equal a total movement linearly of 500mm. The linear movement is 5mm per revolution of the screw with the encoder giving 1000 pulses per revolution which would equal 4000 pulses from the encoder.

The issue here is how to STOP the device at "precisely" 20mm. This may be a good application for an intelligent motor controller or servo motor system.

Does the gear box provide backlash or could a braking system be added to the motor? Unless speed is a big issue I think I would go with the low rpm gearmotor...it may be easier to get the precision needed.

I assume you are on a budget (or this is a hobby) and looking for low cost options? You may want to look at Automation Direct PLC's They offer low cost PLCS with built in HSC (high speed counters)and PWM outputs that may work for you.