Motor Control PLC with a PIC

[sougata]

Hi Everybody,

I have an enquiry for a PLC like motor control app. It would demostrate motor contol drives. Basically 3 blocks.

1. Power Block for Motor Drive (IGBT Based 3 Phase)

2. Controller Circuit (Does a PIC fit in ?)

3. PC side PLC like software for customization and downloading to controller.

It is for a science museum and they don't want to use a professional PLC for cost restriction. I can handle part 1 and possibilliy part 2 if it is PIC based. I am not sure about the PC side software. What special function blocks should be included for a V/F control or DC chopping control. Inputs are tacho for speed sensing, Motor current and voltage (so far I have assumed).

I have downloaded a few PLC docs and not sure that what demonstrations can be given using ladder logic and what using special function blocks or combination of both.

Thanks in advance for any help.

[CosMecc]

On the microchop site is there an application note to control a 3-phase AC motor by a PIC18F4431:

http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=1824&appnote=en020394

It is good explained, and coul be a right starting point for your application.

[sougata]

Dear CosMecc,

I have already gone through the motor control appnotes. It is not the motor control part I am really concerned about, I am confused on the PC side software part. I know I need to develop a PC side application. If you have gone through any PLC software from the Siemens or Crouzet stable then you may know that the PLC contains some special function blocks. These are complex routines that may be achieved through a myriads of ladder logic of relays, comparators and timers. Since this is a demonstration project so I need to write these SFB. For example I can have a ref speed set with a virtual pot then some closed loop options etc. So I really need some insight on how to handle this and what blocks to include and what not as I do not have any experience in PLCs.

[mister_e]

Euh... it's something i never work too much with but do you have any example of those PC software?

I'm pretty sure you can create them in VB, Delphi or else.

From what i feel, you just need to download some screen parameter to the PIC? Serial comm or so?

[sayzer]

Dear CosMecc,

...It is not the motor control part I am really concerned about,...


I guess you have already solved this part with ASM not with PBP.

Or may be, you have some piece of PBP code to control 3-phase AC Motor and if I am more then lucky these days, you can post that code for us to have some reference?

Fingers crossed again :)

--------------------------------

[sougata]

Hi,

Steve what I intend to do is a PC side software with a Flowcode style of visual programming. (I am not sure how much I can achieve though !!) I will have different routines in PIC and a table generated by the PC side software that will have the different constants (pseudo constants changeable on the PC soft). The table will also have pointers that ties up different subroutines on the PIC to make a logical program flow. The PIC would be a 18F4431 perhaps. Where I am confused is the program blocks on the PC soft, parameters in otherwords. They can be a tacho input followed by a divisor, a programmable timebase, current sensing blocks, protection and so on..... I don't know which blocks should essentially make a smart motor controller. As for sayzer, the motor control part is mostly handled in mixed asm+pbp. Relying on entirely asm interrupts. I may use a dedicated chip for the motor control and another PIC to download PC data and run the app. So if anybody can suggest me what should be the capability of the PC soft then I can start at least. Here is a link where you can download a demo version of the PLC soft for Crouzet millenium-III PLCs http://www.crouzet-usa.com/downloads/millenium/Demo132.exe

[mister_e]

Nice soft, it's kind of Labview and/or Softwire.

It's certainely doable, but it will s u c k a huge amount of time to create the user interface and the code blocks.

you have to consider tons of different ways... so a universal PIC program with tons of subroutines to ba used one after the other or some at the same time etc etc etc. It won't be easy.

Use the PC to dump code via bootloader... is handy.

Sure doable. How much time you have for that?

i'll sleep on that, maybe i see that harder than it could be...

[sougata]

Hi,

I need to quote for the project and I am not sure how I would fare up against a commercial PLC. I think a commercial PLC would be cheaper !!! Actually my client wants the students taking the classes to have a clear understanding of Motor Drives and the control logic behind that. Since the application is limited to only motor control functions, I need to define the SFB (Special Function Blocks) before I start the actual coding. Since there would be only two types of motor connected, AC Induction and DC motor so the motor's electrical and mechanical parameters would be quite fixed. May be I should study commercial Motor Drives and write a flexible application to customize it via the PC software. My concern is that the system should be capable to some extent, not just a lame one. Cause it will be used as a tool to to teach college students on drives during summer camp or science fair. It need not be complicated but should have a technically right approach (To get my payments through!!!)

[mister_e]

If you already know the pricing of the competition, but you don't know how much time you need to spend on... it's hard to quote something reasonable.

But on another hand, it could be a nice core for something else on another area. Kind of stuff you sole the IDE first, then plug-ins (or SDK).

1. How much person will buy it
2. How much you can extend this
3. Can this be a single developpement tool
4. Can this replace a compiler
5. Can this allow you to create development board OR dedicated pre-programmed chip
6. Do you have to include some 'Disclaimer' or assume some potential behaviour, material damage

may lead you to the final decision.

Can also be something like Easy HID. It do the program core and user have can play with what you do. You know possibility are endless.

It's a interesting project if you have time and can afford some tech support.

Good luck!

[sougata]

Hi,

Well more than a business interest I was more inclined to the academic interest of the project. As you say "Learning Opportunities". But this is way beyond to be a discrete project sold only once. Still I would like to know the motor control parameters that a PLC should support.

[b1arrk5]

Take a look at Triangle Research. They have a line of inexpensive (I think under a hundred dollars,) PLC's that can be programmed with their software that includes both ladder logic and Basic. Just Google Triangle Research PLC and take a look. I have seen their ads in Circuit Cellar magazine for a number of years now. It might be cheaper and easier to use theirs than to design your own.

Good Luck!

Jerry.

[sougata]

Hi,

Thank you for the Info. I am downloading the simulator.