Hobby Project I'm working on

[sparkie]

So I have a hobby project I've started planning. This won't be in a very harsh environment, so I was kind of thinking about using a fairly cheap PLC and a standard computer with a few modifications to do the controls. There also isn't much potential for danger in this equipment.

I was thinking about using something like a Pi or Ardunio for the project, which would work fine but I would really rather have something that was, in general, packaged a little better.

We have some Modicon OTB's with an RS485 interface to a computer do that do some minor controls stuff at work that are pretty cool. The problem is that they are around 400-600 each for a basic device, and that doesn't count the computer or any of the field wiring/devices.

Do you guys have any suggestions for something similar to this:
http://www.schneider-electric.com/en/product-range/1055-modicon-otb/

I would really like something cheaper, but it doesn't necessarily have to be all that robust. Analog IO would be pretty useful too.

 

[Bullzi]

What are your I/O requirements?

 

[sparkie]

I'm still in initial planning, so I don't have an exact number of IO points per say yet. I know I will need several analog inputs and outputs (around 10 of each most likely) and probably around 20-ish discrete points.

Most likely I will end up going with a 24V power supply so I'm not having to use 120VAC in the entire cabinet. Ultimately I'm aiming for something that can be installed by an electrician, turned on and remotely tweaked/monitored. I will not need anything fancy such as a load cell input or a high-speed counter. There will be very little motion with this.

I will have lots of trending, though it wouldn't be, say, every second. It might be a record taken every 5 minutes or so. That is why I think going with a PC-IO based solution might be the best way, as I can have my cake and eat it too.

To be honest I really don't want to mess with switching small 5V and 3.3V signals and with the equipment. It can be pretty touchy.

 

[Mickey]

Most likely I will end up going with a 24V power supply so I'm not having to use 120VAC in the entire cabinet.

?? What powers the 24VDC power supply?

Ultimately I'm aiming for something that can be installed by an electrician

What would make it not able to be installed by an electrician?

 

[sparkie]

?? What powers the 24VDC power supply?

120VAC of course. All I meant is that I don't want to use 120VAC for the entire system. I would rather switch 24VDC.

 

[willxfmr]

What would make it not able to be installed by an electrician?

Usually anything bigger than an 8-32 screw is enough to get me to stop and call a mechanic....


Will.

 

[sparkie]

It seems we have gone way off topic in this one.

I'm looking for a field IO interface device that is modular and uses a computer for the actual logic processing and controls similar to the Modicon OTB's, but I was hoping there was a manufacturer that was a bit cheaper than their's. It is not going to be in a rugged environment.

 

[Bullzi]

I am not very experienced in PC Logic Control so I may be out in "Left Field" here but wouldnt the software to do the control be the big ticket item? I was just looking at AutomationDirect.com and they sell a program for PC logic control and it is over $2,000 just for the software.

 

[padees]

Usually anything bigger than an 8-32 screw is enough to get me to stop and call a mechanic....


Will.

Trust me, I know electricians that have no clue about thread pitch, and will cram anything in the hole that will fit

 

[engjohn]

You could use automation directs click Plc with Ethernet. Pretty in expensive ~100$
If you don't load a program in the click, you can access all memory locations with modbus and control from anywhere

 

[AGill]

If you don't load a program in the click, you can access all memory locations with modbus and control from anywhere

For my curiosity, are you saying you could just fire the outputs of the PLC remotely via Modbus?

 

[g.mccormick]

For my curiosity, are you saying you could just fire the outputs of the PLC remotely via Modbus?

Yes. If no program in the plc is turning them on/off, then you can turn them on/off via modbus.

 

[engjohn]

Yes, with no program in the Click, you have access to all memory locations. See attached screen cap from the programming software. "Y" memory locations are the outputs. In the picture you can see they are R/W.

 

[padees]

Yes, with no program in the Click, you have access to all memory locations. See attached screen cap from the programming software. "Y" memory locations are the outputs. In the picture you can see they are R/W.

That's pretty interesting. I need some low cost, but dependable, RIO for my hobby project. I'll check into the Click as well. Thanks!!

 

[g.mccormick]

That's pretty interesting. I need some low cost, but dependable, RIO for my hobby project. I'll check into the Click as well. Thanks!!

The click has a large selection of IO also. Analog in/out, AC/DC in/out, thermocouple ins, rtd ins. etc.