TTL output 1 turning ON for no reason

[LeBoutte]

Hi all,
 
My TTL output 1 is turning ON from time to time for no apparent reason. I don't use it so I really don't know why it is turning ON.
 
Any thoughts?

 

[LarrylLix]

Are you measuring a unconnected, open collector, output with a high impedance meter?

 

[LeBoutte]

No but I have a small relay board connected to the first 4 TTL outputs. Only TTL output 1 is turning ON for no apparent reason. And it turns ON at boot/power cycle.

 

[LeBoutte]

Here is the small board.

 

[CAI_Support]

There are two kinds of relay boards out there, some are TTL "1" trigger, some are TTL"0" trigger. What is your board trigger level?  If he board is "0" trigger, please make sure invert TTL output in setup, otherwise, when power not stable, it could cause relay board misfire.

 

[LeBoutte]

The relay board is set to TTL "1" trigger. TTL outputs 1 to 4 are wired to the 4 relays board. Outputs 2 and 3 are used and working without issue. Output 4 is wired but not used and does not turns ON for nothing. Only TTL output 1 is turning ON for no reason. Weird...

 

[CAI_Support]

In your relay picture, three jumpers are set one way, and one jumper set different from rest three.  Was that COM pin 1?

 

[LeBoutte]

The image is from the internet, this is not my board.

 

[CAI_Support]

Since your PLC code does not issue any command to OP1, the relay board misfire would be either problem of WC8 board or the relay board. Could you please watch from GUI screen to see if OP1 ever turn to 1 by itself?  Could you please disconnect between OP1 and your relay board Input 1? Could you please use a volt meter to measure the input 1 voltage to see if when it misfired, would the input voltage change? at what level?

 

[LeBoutte]

It is ON from the GUI screen. I'll do the test next time it misfire. Thanks!

 

[CAI_Support]

If that is ON on the GUI screen, it is either setup or PLC code controlled OP1 to be ON. Did the board set OP1 as inverse output?

 

[LeBoutte]

No, the board set OP1 not inverse. It did not turn ON in the last few days...

 

[CAI_Support]

If GUI displayed OP1 is on, someone must set that ON, otherwise, it would not show on GUI if anything malfunction.  Please check your setup everywhere to make sure nothing in configuration turned that ON.  

 

[LeBoutte]

I checked my setup everywhere and I did not find anything that turn TTL output 1 ON. It seems to turn ON only at boot.

 

[BraveSirRobbin]

I have no idea how webcontrol works...but from experience I know most PLC's will have an 'initial state on boot' setting for outputs (you can have it off, on, or last state).