CArnold

Thanks for the input, I know it's messy, I have only been working with LabVIEW a short time and am not a programmer. I think you are right about the two DAQ assist conflicting with each other. I made a few minor changes and everything appears to be working ok. Although, I know there is a cleaner way to do it and will work on coming up with something different. The machine I'm trying to run subjects plumbing fixtures to 250 cycles of alternating hot and cold water. One cycle consists of 90 seconds of 190F water followed by 90 seconds of 70F water. The machine has four hot solonoid valves, four cold solonoid valves, two zone valves for directing water back to either a hot sump or cold sump, a hot water heater maintained at 190F and a chiller maintained at 70F. When the machine starts, the hot solonoid valves are opened, cold closed, and the zone valves rotated to direct water to the hot sump tank. The heater temperature is monitored and elements are turned on to maintain the 190F. The temp in the chiller is monitored but not controlled as it has a separate control. After 90 seconds, the hot solonoids close, cold open, and the zone valves switch position. After 250 cycles, all relays are opened and the machine shuts down. The solonoids need constant voltage to stay open while the zone valves need seven seconds of voltage to change position. I'll take a look at the tutorials you suggested and try to come up with a cleaner solution. Any suggestions would be appreciated.

Thanks, I tried the help/explain error and am working through understanding it.

I'm somewhat new to LabView and hoping someone can help. I'm running LabView 8.5 using a cDAQ-9172 with a couple of 9481 modules and one 9211 module to cycle hot and cold water in plumbing fixtures. Most of the time, the program works fine. Every now and then I get the following error message and the machine stops functioning properly: Error 50405 occurred at DAQmx write (Digital ID Bool NChan 1Samp 1 line). vi:5 Thanks.