PLC SCADA Communication

manoj,

I recommend you visit the web site of your automation solution provider. Thus because, if you need to take data from the PLC there are a variety of solutions, protocols, and tools in order to achieve that goal. This variety widely explained for your solutions provider (AB, ABB, Siemens, Festo, Toshiba, etc)... there are industrial comunication networks, switches and hubs to upgrade the information onto higher levels in your control scheme.

Good look!

Contact Automation & DCS/ SCADA experts . The few whom I am acquainted are ABB and Yokogava

Hi Manoj,

I have solution for your requirement. please let me know which make and model of plc you are using for your scada. Also let me know which SCADA software and number of PLCs you are using.

Further do you need wireless communication or dial up net work or GSM/CDMA or RF

You may respond to my mail ID aksasee@computronics-intl.com

Regards,

A K Saseendran

Computronics International Limited

New Delhi-110048

If you are looking to log data from remote assets, please feel free to contact me via email at morgan.mark@orbcomm.com. Orbcomm was designed as a transport mechanism for machine to machine communications on a global basis. We own and operate a global LEO, VHF satellite constellation which could well meet your needs. Cheers and I look forward to helping you in the future. Mark Morgan - Orbcomm Inc

Manoj--

Exactly what hardware you need depends greatly on the brand and model of PLC and the type of equipment you are putting at the other end of the communications link(s). It also depends on the size and layout of the system--the length of the communications link, the number of units on it, the topography of the system--and the environment you are in.

I general, you need a data communications port on the PLC that is capable of sending this data over the TCP/IP network. Newer and more expensive units often have an Ethernet port which can do this directly.

If your PLC units do not have an Ethernet port built-in, then you can connect a signal conversion unit to the PLC's serial data (RS-232 or similar) port. These units are available from many vendors, and do not have to be the same brand as the PLC. Some also provide optical isolation of the signals. They have different ways of being powered, but most require a separate DC supply (which can often be taken from the DC supply terminals the PLC has for its I/O. Some of these units also can do communications protocol conversions and interpretations, so a PLC can be made to talk in Modbus or many other types of protocols. The conversion unit must be able to have an address so data from it is identifiable as to source and data being broadcast is used only when it is directed to this unit. In the USA costs for these can range as low as $100 for a low-quality with very limited use, to over $600 for those with many features (including such things as changing the signal speed and memory caches). You have to be careful when setting up the serial port for data communication, because you need to choose the right parameters (in some cases the data port and the programming port are the same, so when you download the new parameters you can instantly lose programming ability until you reset the PLC to its factory defaults by another means).

At the host end, you will need to have a means to interpret the data you are receiving and to translate data being sent into the form the PLC recognizes. This is usually a software, not a hardware issue. Which software you need will depend mostly on the brand of PLC you are using. Finally, the host computer will need a program which can present this data in a form that the operator (or some automatic program) can use.

Other questions can arise, such as: Does your network have one host and many slaves, or can more than one unit be a host? Does your PLC automatically use the desired protocol and parameters on the network or do you have to code its operation into the operating program? How will the network operate when one unit fails--will it lock-up or is there a means of recovery? Can it resume automatically after a power failure?

Data communications networks are composed of many layers, which must work together. Your post mentioned the hardware layer, and my answer was talking about three layers (hardware, protocol, software). Other layers are the physical layer of the network cabling, the operating systems of the devices on the network, and layers which can allow data to be transmitted over interconnections between networks (this last allows me to view the operation of a PLC in a warehouse while I am at home 700 km distant).

--JMM