6509 digital in problems

[RJHLJH]

I am using a port on the 6509 for digital input lines. I am observing quite a bit of crosstalk between the lines causing false readings on the the digital ins. The lines are tied to float switches to indicate fluid levels of various tanks. As soon as a low signal is erroroneously observed, this trips a fault which shuts down power to this tank loosing valuable run time. I plan to use a pull up resitor applicataion to clean up the float switch indicating. I want to wire a 1K resistor from the 5V terminal to the high input of each digital in line, a total of 8 resitors of the 5v terminal. The float will be wired also to the high side and then back to digital ground. With this I expect to see a digital high when the float is down and a digital low when the float is up. The current consumption should max at 5mA X 8 digital in lines equaling 40mA maximum which is well below the board specified 1A on this terminal.

Does this seem like a reasonable approach to the problem I am seeing? Any advise or suggetions is appreciated.

[Tom_W_[DE]]

Hi RJHLJH-

That configuration sounds exactly right for the operation you would like to achieve. I think it is more likely that you're seeing noisy glitches in operation rather than crosstalk because the float switches might be making loose connections or rapidly switching operation.

Please post back if you have any additional questions.

Thanks-