WHAT I HAVE
I have put together a simple little mobile trolley on rails with a: Stepper Motor, wheels, serial Controller/Driver Unit, gripper, and pneumatic cylinders (total of 10 air solenoids). I am running this connected to my PC using hyper-terminal to pick and place at different slots. I was surprised how easy and inexpensive it was to get this far, and it even works.

WHAT I WOULD LIKE IS
-Simple dependable movement to location.
-Verification of positioning at the correct slot.
-Reading of the bar-code on the Picked-Up item
for verification.
-Retrieve and write location and item
information to shared SQL database files.
-Operation through PC Ethernet Network.
-Ease of set-up and operation.


QUESTIONS
-Which PLC should I be using?
-Should I be using an AC motor with Inverter or
the Stepper?
-Should I use a shaft encoder or count my slots
with a Photo sensor to verify location?
-Should I have functions and information on the
PLC or on a networked computer?
-Should I be writing a Visual Basic program or
looking at which software?
-Since all this is moving is using my wireless
network the thing to do?

I apologize for my ignorance and would appreciate any help, guidance and sources for information. Please keep it simple though. (I flunked out of Engineering school and got a Business degree.)

Thank You Very Much

[email protected]

 

Well, it kind of depends on what you want for the end product. If the motion you have now suffices, then simply going to a little PLC Direct PLC should do what you need. If you are going to scale up to a motion system using servos rather than steppers, any one of our controllers will do the job with no PLC at all. My guess would be either our EZ PMAC (ease of integration) or our PMAC2-PC/104 (cheap). Whether you use a PLC Direct system or our stuff, a VB interface is probably the cheapest and quickest HMI for a system that does not require any high speed data transfer or extremely complex high speed calculation.

Davis Gentry
Delta Tau Data Systems
804.795.4288

 

Hi,
This may be a bit of over kill but, have you ever thought of something like Machine Vision. Try something like the DVT 500 series cameras. They can do your Barcode verification, Position refrencing. All with feedback over ethernet. These systems are quiet common and work very well. Other than that same as everyone else small PLC (anyone), VB, Stepper / servo I don't know - I've away from that stuff for a while.
Hope this helps a bit, or at least gives you more options.
Regards,
Paul Pierce.

 

This is an example of the 90/10 rule: To get 90% done takes 10% of the time. That last 10% takes the other 90 :^). If you can locate dependably
with proc switches, it would be far simpler that tracking with steps, dealing with wheelslip, etc. or using other, more dependable position sensors. A target at the center of each bin is simple. Since you are going to have a PC already, why add a PLC?. Most of the things you want are easier on a PC and all can be done fairly easily. If the stepper is fast enough, and strong enough. use it. Add complexity only if you must. Since you know at least some PC programming, I doubt you would save time or money by adding a PLC. I would tend to do the control with something other than VB, but if your display requirements are 90% of the project even that might be justified if you can get it to run fast enough and stay working. If you use a proc on the trolly and just track bins, the speed requirements are minimized. The whole trick is to realise what is good enough and what you have to upgrade for reliability.

Regards

cww