Wiring Outputs pnp

[Vinicius]

Hello,

I'm struggling to understand why do I need to connect +VO and 0V to the outputs, how shows the image:

I tested  here and only with de +VO (24V) worked well.

[kratmel]

Hi,

I will try to describe why it works without a connection.
1) There is  output board inIside of the Unitronics OPLC controller.
2) Each of the solid state outputs is a part (one channel) of the few  chip VN340SP (or something like that on foto).

3) To send signals from the processor to this chip, we must have one common wire and several separate ones for the required number of outputs. This common wire also neded for power the VN340SP.  This wire is the OV contact you specified.
4) This OV contact is connected to the main power OV contact of the PLC panel through a small fuse (you can check with a measuring device that the resistance between the 0V and 0V contacts is not equal to 0 Ohm).  For example i post foto of little fuse and 0V power connection for SAMBA SM70 board.

 

That is why you output operate with  0V not connected.

5) If you neglect to connect this contact, it may happen that the fuse (or another cirquit) inside PLC blows and all your outputs stop working.
     
Conclusion - always use the connection RECOMMENDED by the manufacturer.
This will save your controller from problems and save you money.

[Isakovic]

Great topic. I have a question for eminent wizard kratmel.

Is it recommended or not to use different power supplies for main power and output power? If both are referenced to ground I guess not, but what if they are floating?

I remember a case when I had safety circuit cut +VO line as a bonus security on Jazz unit. This rebooted PLC when activated so I don't use it anymore. Why was this happening? It was the same supply for PLC and outputs.

[Vinicius]

19 hours ago, kratmel said:

Hi,

I will try to describe why it works without a connection.
1) There is  output board inIside of the Unitronics OPLC controller.
2) Each of the solid state outputs is a part (one channel) of the few  chip VN340SP (or something like that on foto).

3) To send signals from the processor to this chip, we must have one common wire and several separate ones for the required number of outputs. This common wire also neded for power the VN340SP.  This wire is the OV contact you specified.
4) This OV contact is connected to the main power OV contact of the PLC panel through a small fuse (you can check with a measuring device that the resistance between the 0V and 0V contacts is not equal to 0 Ohm).  For example i post foto of little fuse and 0V power connection for SAMBA SM70 board.

 

That is why you output operate with  0V not connected.

5) If you neglect to connect this contact, it may happen that the fuse (or another cirquit) inside PLC blows and all your outputs stop working.
     
Conclusion - always use the connection RECOMMENDED by the manufacturer.
This will save your controller from problems and save you money.

Thanks Kratmel, this was quite enlightening!

[kratmel]

12 hours ago, Isakovic said:

Is it recommended or not to use different power supplies for main power and output power? If both are referenced to ground I guess not, but what if they are floating?

 

Use different  power supply possible only when output  is "isolated". Fof example V200-18-E3XB  has 2 isolated pnp/npn (source/sink) transistor outputs and  4 isolated analog outputs.  However, the user must remember that these separate power supplies must be turned on and off at the same time or in the correct sequence. As an option - start powering the panel and then power the output - and turn it off in reverse order.

12 hours ago, Isakovic said:

I remember a case when I had safety circuit cut +VO line as a bonus security on Jazz unit. This rebooted PLC when activated so I don't use it anymore. Why was this happening? It was the same supply for PLC and outputs.

The PLC uses output drivers that are protected against short circuits, overheating and usually undervoltage.
Turning off the driver power (in your case + V0) could trigger one of these protections - and accordingly cause the PLC to restart.
It's just a theory - I don't have a Jazz panel with transistor outputs to investigate your case.

Therefore, a second CONCLUSION should be made - the user cannot use separate power supply for solid-state outputs of the PLC, unless the instructions indicate that they are isolated.

[Isakovic]

Thanks, I learned something today.