Electronic switch for profibus communications


Thread Starter

m griffin

Here is my idea. Please find the holes in it. We have plans to install distributed I/O (AB flex) in class1 division1 location. I can install my non-intrinsically safe devices in a purged panel and install it in the class1 div1 area. When the panel loses pressure the purge unit will disconnect the power source to the panel. So far so good. But my communication cable(profibus)is still powered. This is a problem. I know you can use Profibus-PA(intrinsically safe) but the I/O adaptor modules are not in themselves I.S. So
that is the reason I'm not using Profibus-PA.

Anyways my idea is to disconnect the communications via an electronic switch. The electronic switch is then swiched off via a relay to ensure no power exists. I don't want to switch the communications cable directly through the relay. It seems too crude ie contact bounce from the relay. IS THERE AN AVAILABLE ELECTRONIC SWITCH TO SWITCH OF THE PROFIBUS COMMUNICATIONS?

Gabriele Corrieri

I think that you cannot disconnect profibus connection, because entire bus will stop, because the token will be broken when arrive at disconnected station ...

Hope this help

Gabriele Corrieri

Donald Pittendrigh

HI All

Run Fibre optic into the panel and use a converter. Set up the Profibus to ignore the station which is not reporting... problem solved.

Donald Pittendrigh
Fibre optic? It's all about cost my friend. I've looked into it and the cost is formidable. This is why I'm trying to find a means to disconnect the profibus communications.

Gilles Allard


You can use a repeater and switch off power to the repeater when your panel is not pressurized.
I would install the repeater in Div 2. Be sure the terminator of your main Profibus segment is not on the repeater. Powering it off would remove the biasing voltage from the terminator.


Donald Pittendrigh

Hello my Friend and others

Profibus cable is more expensive then fibre optic cable, at least in my country it is, and for a point to point link on plastic fibre you can get 2
X OLP's from Siemens at around USD50 each, and then the termination of the fibre should cost you about USD35 per plug, if you consider this to be real expensive then I would venture the opinion that you are in the wrong market...... my friend.

Please call with order number for design and supply of the appropriate system components.

Bye now
Donald Pittendrigh