Allen Bradley Question; Triggering a HTTP link

I was wondering if there is some possible way to trigger a HTTP link through a web enabled AB PLC. Such as this "http://tftmonitor-swa/forms.htm?led4=1&led3=1&led2=1&led1=1"

It is an embeded device we are trying to trigger via PLC.. We can't run a OPC server on it..

Any other ways of doing this? I'm ALL EARS!

Thanks Very Much

Jaron

I assume that HTTP link points to your specific device on your network, rather to an Internet site.

What exactly is the device ?

It sounds to me like you need to execute an HTTP POST function.

The EWEB modules might be able to do this; these are the 1756-EWEB, 1768-EWEB, and 1761-NET-ENIW.

Which A-B controller are you using ?

Thanks for the quick Reply Ken!

I'll give you the low down..

At my company we are working on a network controlled apparatus. It can be controlled trough a network using the platforms integrated HTTP server.. Using this board http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=1406&dDocName=en028217

It uses Ajax.. Anyways we plan the apparatus to be used in industrial applications ect.. So we want to present an option to be controlled via a PLC AB for custom setups and control..

Now with no capable opc server... the easiest way I came up with is controling it with a link such as http://tftmonitor-swa/forms.htm?led4=1&led3=1&led2=1&led1=1

YES its local...

after the /forms.htm? are the commands... in this case just turning on LED's Posting the link works great...

What do you think is the best way to integrate this into a AB PLC. Require the EWEB module? and have a Control map in the products manual?

Thanks so much guys

Jaron

Run Wireshark on your computer when you click that link, and it should show you the full text of what the computer is actually sending; I expect you'll find that it's a HTTP POST but I can't be sure.

The easiest thing from an A-B controller programmer's perspective would be to implement a subset of the EtherNet/IP stack in the PIC-controlled unit. Second-easiest would be to implement a subset of Modbus/TCP.

And the most complex and expensive thing from the A-B controller programmer's perspective is the EWEB module, which of course is easiest and cheapest from your perspective.

Implement a subset of the EtherNet/IP stack in the PIC-controlled unit. Second-easiest would be to implement a subset of Modbus/TCP.

Can you explain this a little more

I don't have much experience with the above. I'm all ears

Heres the WireShark

Go ahead and zip and post the whole *.PCAP file; I'm curious to see the details.

Edit 1: I'm pleased to see it's an HTTP GET... that should be easier.

Edit 2: Does your little PIC board implement SMTP (e-mail) protocol ? You might be able to fake this by sending an e-mail, which more A-B controllers support.

Attached! Thanks Ken

Ken Roach said:

Go ahead and zip and post the whole *.PCAP file; I'm curious to see the details.

Edit 1: I'm pleased to see it's an HTTP GET... that should be easier.

Edit 2: Does your little PIC board implement SMTP (e-mail) protocol ? You might be able to fake this by sending an e-mail, which more A-B controllers support.

Click to expand...

Yes Ken It does have a SMTP protocol, it is an HTTP GET.. What do you think I should first attempt?

If there is a way to have your device parse the contents of an e-mail, that would be my choice. The A-B ControlLogix supports a simple SMTP client in the ordinary 1756-ENBT Ethernet module (rather than the much less common and more complicated 1756-EWEB). I don't know which CompactLogix controllers (if any) support SMTP.

Happy Monday!

I talked to one of the engineers working on the project... He thinks the SMTP idea would add to much latency, I agree..

So now I'm down to require a EweB or edit the stack.. Which I don't have much knowledge about...