logic relays

[Guest need_input]

Has anyone used any of the logic relays for simple control? I have noticed "pro-io" from proface america (pro-io.com) and may have a need for such a device. There are others on the market but I don't know of anyone ever using them. What are the pros and cons of such a device? Any feedback is welcome.

[JimRowell 1]

I've used a couple of different brands on a few occasions. They are VERY limited in my opinion. If you are doing something very simple, they can be a cheap option. Trouble is, they are a little expensive as a timer and it's hard to do much more than that. I found it was so time comsuming trying to cram projects into them that it left a bad taste in my mouth. I think if you have a simple use that you are going to reproduce in some kind of quantity than the low hardware cost might be worth it. But for me, one-off projects have a way of growing beyond initial expectations and the ones I used just didn't have the programming software or the commands to do the job. I took a Mitsubishi apart once and was shocked at the apparent power that lives inside. Too bad it's not accessable. I'd rather spend a little more and have a real PLC. Jim Rowell

[Sleepy Wombat 27]

I have mainly used the Omron ZEN's...like Jim says, they are limited, however in the app's where there are more then one timer required they are excellent value. I believe that you can download a trial version of the ZEN software from the Omron site. The beauty of the softare is that you can actually simulate and test you code without being plugged into one...pretty cool. thats my 2 cents

[Crossbow 295]

I've used the Siemens LOGO and Mitsubishi Alpha units. I have to say the LOGO is more expandable and has quite an instruction set. The Mitsubishi unit, while not expandable, has a good instruction set too. I have a customer that buys these things 10 at a time, and uses them for simple conveyor control applications. For applications where you would use a couple of timers and counters, or for some simple sequencing, they are excellent and cheap. I can post some sample code from some of my past applications if you'd like. The only two major limitations is that these 'smart relays' don't offer math commands or communication capabilities. But for what they are designed for (simple logic, operator interface, and ease of modification of program) they are great.