I'm trying to collect data from two locations in our plant. At each location I want to collect a temperature (analog - 4-20 ma) and an on/off (digital 120 V) signal.

Neither location is currently wired in any way for data collection. Ethernet is nearby, but wireless would be great as well. They are close enough together that a single wireless access point could most likely talk to both.

Other locations in the plant use networked Automation Direct PLCs. These PLCs also perform control functions. I collect data from the PLCs via the Automation direct DDE server and write it to an Access database using a <b>custom</b> Visual Basic program. This system certainly has its limitations and I'm open to another software package.

I have looked at using Automation Direct Field I/O or an additional Automation Direct PLC. For those solutions I'd be spending $550-$900 per location, plus wiring costs. It just seems like overkill to get 4 analog i/o and 8-16 digial i/o and a whole plc when I just need a couple inputs.

I'm not tied to my existing system, just putting it out there for information. So any suggestions for inexpensive network data collection?

 

There are remote I/O devices with ethernet that combine digital and analog interfaces.
For example:
http://www.moxa.com/product/ioLogik_E1242.htm

But you may find more products like that and eventually with wireless instead of wired ethernet.
I would prefer devices which support Modbus/TCP.

They could be controlled via a PC somewhere in your plant. This can be done using our open source framework for SCADA
http://pvbrowser.org

 

Sounds like a good application for a Banner Engineering DX80 wireless system. You can get nodes with 2 analog inputs and 4 discrete inputs and they communicate wirelessly to a gateway that gives you Ethernet Modbus TCP.

As far as a SCADA package goes, Indusoft is a good, low end, scaleable, inexpensive product.

 

I successfully used a Phoenix Contact wireless device to send analog and digital signals from a remote location (in a different building, ~200' @ 900 MHz) to a local PLC I/O. If you have spare analog and digital points you could use this method. If you have a good line of sight between the receiver and transmitter then you can consider 2400 MHz (less interference but more demanding signal path).

The link to the datasheet:
http://rd.phoenixcon.com/products/interface/db/datasheets/2875_en_A.pdf

Regards, Russ Kinner
Phoenix, AZ USA

 

Thank you all for your suggestions. You brought up some very interesting ideas and I am exploring each of them.