Back to top

Input staying on dispite signal being off

0 votes
+ vote
Vote up!

The problem was the machine would just not index from time to time

At some points the input 1 would go high and then just stay high on the scope
voltmeter on input showed 0 volts and it was still showing high on the scope

scope traces show results of testing with different input settings for the filter

Why is this input staying on ?

I connected the same signal to input 1 and 5 at the same time  and tried different values on the input de-bounce filter

image

Input 1 and 5 wired to the same signal

2.63ms

At some points the input 1 would go high and then just stay high
voltmeter on input showed 0 volts and it was still high


image

 

Input 1 and 5 wired to the same signal

1.6 ms
Machine seemed to work normally on this setting.




image

 

0 Comments

2 Answers

0 votes
+ vote
Vote up!

yes its an akd as shown on the screen shot
 

Why would input 5 behave properly as shown on the scope screen
its the same signal and the same common
same input signal
2 different responses
image


 

0 Comments

0 votes
+ vote
Vote up!

John:

I am guessing your using an AKD drive? If not, please let me know and ignore the following suggestions.

1. I am 80% sure you don’t have a parameter setting issue. Only parameter that could impact the digital inputs is the DINx.INV parameter, called “polarity” on the workbench screen. You would have to be toggling this parameter, it doesn’t change on it’s own.
2. AKD digital inputs are “ON” with just 5VDC to 30VDC potential across the digital input common to the digital input. Polarity doesn’t matter. When you measured the input, did you measure directly from the X7 & X8 terminal on the drive. Example: X7-10 to X7-1 and X8-6 to X8-3
3. Some PLC’s digital outputs don’t like the low input current of the AKD. The output will turn “ON” but there is not enough current to turn it “OFF”. Can you run a test by manually exciting the digital input? Example: touching the digital input wire to +24V?
4. Open common is a fun issue to find. Your digital input is wired correctly but you don’t have a direct electrical path between the AKD’s digital common terminal and the 24V power supply common. So the AKD’s input behavior is dependent on other 24V devices being turned on or off.
5. What about AC across the terminals? You said “0V” so I am assuming your measuring DC voltage. The digital input do have a diode that will rectify AC into DC and turn the input on.

For me to be more helpful, I would need more details about your project including connection diagram and drive parameter file.

Dan Wolke

0 Comments
ANSWER THIS QUESTION
You may login with either your assigned username or your e-mail address.
The password field is case sensitive.

If you do not have an account, click here to register.