drivers station digital input trouble

[finman]

on our control board, we have several switches that i have wired to digital inputs on the drivers station console. in labview i have made an indicator light that should light when the circuit is open. when the circuit is closed, the light goes off as it should, but when it is open, it flashes on and off. even when i connect a pwm cable with NOTHING on the opposite end, the light still continues to flash. any ideas why this is happening?

[kevin.li.rit]

How are your inputs wired? The inputs of the drivers station contain no pull up or pull downs so you have to wire them yourself or you might get some in between state when they are open.

[BitTwiddler]

Here's how I've been telling our electronics team to wire up switches connected to the Driver Station digital inputs.
It shows how to hook it up when your switch has two terminals or three terminals.
Normal convention is that when a switch is in the "off" position, the signal line provides +5 volts and ground when "on" so you may see the opposite of what you expect in your programming but its usually easy to invert the sense of the switch.

[Wylie99998]

something similar happened to us : [ we found that using pullup resisters on our buttons that were connected to the digital inputs fixed the problem

[Al Skierkiewicz]

Chris,
Without the pullup resistors, the high input impedance of the devices used, can respond to anything including your hand, a closeby radio station, even a CFL or a plasma TV screen.

[Andrew Y.]

is there a special resistor i need to use or will any 1k resistor do?

[kevin.li.rit]

I've been using 10k ohms. 1kohms should be ok.

[finman]

we got it, thanks everyone

[kushvp]

how exactly did you solve your problem? we are have the same issue.

[Al Skierkiewicz]

You must use and external pullup resistor for digital inputs on the DS.