Found threads from past regarding SPI Backplane PLC. I was wanting to design one myself and found these threads from searching Google. Just became a new member to Control.Com. I apologize if this is redundant request. I just could not find any updates since about June of 2011. I am very interested in this endeavor and did not want to start from scratch if this is still moving along.

Thank You,
Lee Engler
[email protected]

 

Hello,

I had something to do with that discussion and project, but it didn't take off as far as I know. The biggest problem (in my opinion) was the lack of a good mechanical system. The choices at the time were to make a simple header to backplane connector and use custom sheetmetal and store bought guide rails to form the chassis. Maybe some of the hardware from rack mount chassis could be used (VME or cPCI type extrusions) but for a typical PLC you would want to trim down the size of the cards significantly (3U cards are quite big to fit in anything less than a 12" deep enclosure). What it boiled down to was that without some funding one of us was going to have to hand off significant personal cash just to buy parts, or alternatively end up with a cheap looking home brew system that nobody would take seriously (again, my opinion).

At the same time I was introduced to Beckhoff Ethercat IO system and soon realized that a central computer to this IO interface would truly replace the backplane entirely for applications up to approx 8Khz (most of industry, in other words). For me a system like this for medium to complex machines is nice, and a simple "Brick" PLC for everything else covers all bases. Lately I have been admiring the HMI/PLC all in one units for small applications but selected one yet.

Good luck. I have a rough spec at home, but its really not much and there are undoubtedly errors and omissions. Let me know if you would like to see it.

KEJR

 

My main purpose was for a custom I/O card that is not supplied by any current manufacturer. Mine would be for one off personal use. Mainly curious how the SPI part of this worked out over a back plane. Mechanics are not as much an issue for personal use.

le

 

Hi Lee

I did get boards made, but my project was interrupted by life and I haven't been able to get back to it. It will be much easier now if I can get the time. All that stuff is at my previous house. I'll be starting it up again one of these days. I'll announce when I do.

Regards
cww