small PLC with ext.temp.range ?

Mitsubishi's Fx1s PLC will do the I/O and the comms (through the programming port) you require but the temperature range you quote is a bit hopeful..

The Mitsubishi literature quotes -20 to +70 degC *storage* temperature limits, but only 0 to 50degC for operation. -20 to +70 is pretty extreme.. You can't air-condition your cabinets?

Hope this helps, Cameron:-)

Simens have special harsh environment versions including extended temperature range versions of their S7-300.

This was cut and paste from the Siemens CA1 interactive online catalogue

There are two versions of the S7-300:

"Standard system; temperature range 0 to 60 °C

System for a wider range of environmental conditions: temperature range -25 to +60°C; the system for greater stresses due to humidity, dew and frost. Can be used directly on vehicles or outside buildings in an IP 20 cabinet protected against direct sunlight and rain or splashed water. A weather-proof cabinet and IP 65 housing are not required. Special modules are available for the system for a wider range of environmental conditions, which can be ordered separately. "

So although this does not meet all of your requirements it gets close

-25C to 60C instead of -25 to 70C

You will need to talk to Siemens

Check out IFM (there are others who do the same thing), IFM have something called the ecomat100 range of controllers. They are rated -30 to +75 degC and storage -40 to +90 degC. They are easy enough to program and they start off fairly simple and small and can be extended. They are packaged in a steel box (225mm X 153mm X 43mm) that is IP67 - so you don't need to repackage them and the digital (or discrete for Walter) outputs will drive up to 2 Amps.

They can do serial but I would use the CANopen port on them.

Cheers Steve B.

Zdenko wrote:

I think to achieve extended temperature range involves reducing the clock frequency to to reduce heat buildup, using ceramic encapasulatated chips instead of plastic ones (to match thermal coefficiennt of expansion at the IC pin-encapsulation joint and using PWB (Printed Wireing Boards) with quartz-epoxy instead of glass epoxy makeup for thermal coefficnt of expansion matching.

To cope with condensation resist screening of the trakcs of tropic proof potting of the board is often used to prevent short circuiting of signals.

Opperation to 70C should not be too difficult with good designe and I believe opperaion at up to 125C is possible with very carefull designe.

Not having to use aircondition is a big advantage in field installations.

Nevertheless airconditioning is a good idea whrever possible. Every

Check Schneider Automation Modicon Compact PLC. It is certified for extended temperature range. I know they used it on trains running thru Siberia. There is Schneider office in Zagreb. Or visit