You can easily accomplish this using the H-series HostLink command protocols published in the H-series User's Manual. Basically, to turn on output, send the following ASCII string to T28H-Relay:
@01WO00nnxx*
I assume the PLC's ID is 01 and the WO command means "Write Output". 00 is channel number for output 1 to 8. nn is the hexadecimal representation of the 8 bits that is to be output 1-8. Eg. to turn on output 1,3,5,7 nn = 55 (hex).
xx is the FCS that need to be computed. However, you can also use wildcard FCS = 00 in place of it.
You can find Visual Basic sample at our website:
http://www.tri-plc.com/ioboard.htmNote: For quicker response regarding questions related to Triangle PLCs at the "Technical Support" forum.