APN for Mobile IoT

[Joe Downie]

Hi just setting up a V350 with Cinterion EHS6T GSM Modem. We have to somewhere put in an APN (Access point Name) has anyone done this before? Appreciate your assistance.

[Simon]

Hi Joe,

It sounds like you are setting up GPRS.  There are a number of steps, and Unitronics provide an example program.  A lot of PLC programming tasks can be solved by trial and error, I don't recommend that approach for GPRS.  Find the example and understand it.  They are installed with the Visilogic installation:

C:\Program Files (x86)\Unitronics\Unitronics VisiLogic_C\Examples\Version 900\Project examples\Communications\GPRS

Specifically on your question. the APN is entered in the "GPRS Register to Network" function block:

I hope this helps,

[Joe Downie]

Hi Simon, thanks for the  info it gives me more to think about.  We are trying to acheive a few different actions with the gsm modem.

1. Ability to log in to the PLC Web Server

2. Ability to send a weekly csv. file via email

3. Ability to send text msg for alarms

Do you think it has this ability

Cheers Joe

[Simon]

Hi Joe,

I've worked with modems and communications on Unitronics for many years.  They do certain things extremely well and we have seen many successful applications.  More detailed comments and advice are below:

1. Ability to log in to the PLC Web Server

   - This is the most difficult of your 3 things to achieve over GPRS.  You need at least a public, dynamic IP address. Once the GPRS connection is active, you then need a way to find the current IP address of the modem.  One option is to get the PLC to send its IP address to you in an email once it has connected to the network.  Note that this is not secure, anyone who figures out the IP address and what device is at the oter end can start to try and access it.

2. Ability to send a weekly csv. file via email

    - this works reasonably well, the nice thing about sending emails is that the IP address does not need to be public.   However with the Vision family, you need an email server that can accept unencrypted connections.

3. Ability to send text msg for alarms

    - by far the easiest thing to do with the EHS6T and a V350.  I would only recommend this modem to do SMS and nothing else.  Trying to mix GPRS and text messaging is not simple, as the PLC to Modem communications has to be reconfigured for each mode (SMS or GPRS).

Overall I found GPRS to be a fragile and difficult method of setting up a data link.  If you want to use the web server, I would recommend switching to an Ethernet modem, which would also require the V100-17-ET2 card for the PLC.  With ethernet you can do things like Dynamic DNS or VPN as a way to maintain a connection to the unit's IP address.   However when switching to Ethernet, there is no easy way to keep using the SMS feature at the same time.  The simplest workaround for that is to send all alarms by email, as most people now receive emails on their phones.  SMS is beleived to be "reliable" but the SMS standard allows 24 hours delay in delivering the message (I heard a rumour that has been increased to 48 hours).

In short, from my experience,  it's not possible to do all 3 tasks that you have described with a single device/single connection, using just the standard built-in features of Unitronics.

If anyone can improve on my advice, I'm happy to be corrected.

 

 

[Simon]

Note also that you can use an ethernet modem and a serial modem simultaneously on the V350.  I have seen applications that do this.  The obviously (and only) downside is the need to have 2 modems and 2 SIM cards.

[Joe Downie]

Hi Simon, you are a wealth of information, you make some good points! Let me look into this a but further and I will get back to you.

Best Rergards

Joe

[Joe Downie]

Simon, I am still working through the problems, but i did forget to mention that in some cases we may have a remote unit communicating with the PLC over Modbus.

Simon Thanks for you time to Assist me, I do Appreciate It.

Thanks again Simon, will keep you posted.☺️

Best Regards

Joe Downie

[Simon]

No worries, my pleasure.  And yes, local Modbus comms is definitely another complicating factor.  It's a bit like the old riddle, I have a fox, a chicken and a bag of wheat, I need to cross the river, but my canoe can only take 2 things at a time...