Contact Voltage?

[d4rkm4n 2]

Hi guys.

During trobuleshooting one of our machines, I found that some DI modules give 24VDC when contact is OFF and 0VDC when contact is ON.

Is there anywhere I can configure and change that setting?

Thanks.

[Gambit 326]

Which PLC are you using ? FX .. In that case it depeands on how the S/S is connected.

If you connect 24V to the s/s than you get an High signal when 0V is connected to the input.
If you connect 0V to the s/s than you get an High signal when 24V is connected to the input.

 

[d4rkm4n 2]

On 3/17/2023 at 4:05 PM, Gambit said:

Which PLC are you using ? FX .. In that case it depeands on how the S/S is connected.

If you connect 24V to the s/s than you get an High signal when 0V is connected to the input.
If you connect 0V to the s/s than you get an High signal when 24V is connected to the input.

 

Hi, sorry takes sometime to reply.

Yes, our PLC was FX3U.

So meaning the one connected to S/S will be common right? Is 24V is + and 0v is -?

Btw, I found the output also act the same way, when DO is ON, it give 0V and 24V when OFF. Is it also based on S/S wiring?

One thing I cannot understand, the DO give 0V when DO is ON but when we check contact at contactor (output receiver), it received 24V.

[Gambit 326]

5 hours ago, d4rkm4n said:

Hi, sorry takes sometime to reply.

Yes, our PLC was FX3U.

So meaning the one connected to S/S will be common right? Is 24V is + and 0v is -?

Right !!!

 

5 hours ago, d4rkm4n said:

Btw, I found the output also act the same way, when DO is ON, it give 0V and 24V when OFF. Is it also based on S/S wiring?

One thing I cannot understand, the DO give 0V when DO is ON but when we check contact at contactor (output receiver), it received 24V.

 

[d4rkm4n 2]

18 hours ago, Gambit said:

 

 

Same for DO?

[Ron_S 61]

D0 or DO? 

However, the outputs can be supplied on the common terminal with 0V and 24V can be the common for the relays/contactors in the panel.

It's the practice in Japan and often Chinese machines. The S/S is just for input signals

[d4rkm4n 2]

On 1/3/2024 at 8:19 PM, Ron_S said:

D0 or DO? 

However, the outputs can be supplied on the common terminal with 0V and 24V can be the common for the relays/contactors in the panel.

It's the practice in Japan and often Chinese machines. The S/S is just for input signals

Digital Output.

Is there any where I can study detail on this?

I just confused how the whole, output can send 0V. 

Btw, I also wondering, how do I know the VDC value should I get at DO point when the signal is ON/OFF?

As for DI already clear, need to check which one is connected to S/S.

Edited 5 January by d4rkm4n

[Ron_S 61]

If it is wired with 0V at the common terminals - then 24V will be the common for whatever the outputs are powering.

When the output is off, the 24v will come back through the coil (giving a false 24V really)

When the output is on it will now be 0v (or negative)

[BobLfoot 302]

Many EONS ago I worked for a Japanese concern satellite plant in the US.  Was always fun when a local system integrator built a panel and 0V was tied to ground where the Japanese panels all had +24VDC tied to ground.  Every once in a while an electrician would forget which flavor of panel he was in and you'd wind up with both 0V and 24V tied to common ground.  Power Supplies don't really like that case.  LOL