IanW

Hi, I am using a TECO SG2 PLR to produce a PWM output that switches a MOSFET smart switch (VNB35N07). I have tried PWM periods of between 200mS and 1000mS. The MOSFET is switching an inductive dump load across the output of a small generator. The switching works well when the duty cycle is up about 40% but when the duty cycle approaches 50% the MOSFET starts to oscillate at 500Hz causing incorrect dump load operation and also excessive heat in the device. I wonder if anyone has experienced similar problems when using PWM FET switches. The drive signal looks quite clean the gate but the oscillations appear across the load resistance when monitored with a scope. Does anyone know the reason for this behaviour and possibly a cure ? Any help would be greatly appreciated Kind Regards Ian

Hi... I'm new to the forum, so Hi to everyone ! I am also new to PLC and SCADA programming and would like a little advice if possible. I have a networked Flexlogix PLC communicating with RSView Supervisory edition via the RSLinx OPC server. What I want to do is to be able to read a file with integer values in (say 100 values) into the SCADA program and send them to consecutive registers in the PLC. So far I have tested the OPC link by creating a SCADA screen with a numerical input box mapped to the first value in an array of integers on the PLC using the appropriate tag, then I read back the tag and display the value in a numerical display...this works fine I have also used a bit of VB code attached to a button to read in a text file containing integer values and then stored then after conversion from string to integer, but I cant seem to find a way to get the values from the VB code onto the PLC via the OPC server. Is it possible to access the OPC server from VB code ? I have found OLE and ActiveX components and wonder if it would be possible to import values directly from a spreadsheet ? Can a single tag be used to reference an array rather than just a single value ? Finally I wonder if there is a better/simpler way of acheiving what I am trying to do.......any hints or tips would be gratefully received ! Thanks in advance Ian