Sourcing & Sinking

I want to know why we prefer Sourcing at Input and Sinking at output ?

pkb2050 said:

I want to know why we prefer Sourcing at Input and Sinking at output ?

Click to expand...

We over here in Europe don't. So it's a regional thing. You could also ask why in some countries they drive on the left side on the road, while in other countries they drive on the right side.

Regards,

metwally.mustafa said:

what is the difference between sourcing and sinking in case of servo drives?

Click to expand...

The same as with PLC inputs and outputs.

Regards,

Hello Mustafa;
The terminologies "sourcing" and "sinking" apply to the status and wiring of digital inputs and outputs.
The following FAQ form Siemens might give you insights into the distinctions:
http://support.automation.siemens.com/WW/view/en/23451499
So if you are connecting between the PLC and the servo using digital signals you might have to refer to these definitions. If not, they are not applicable.
Hope this helps,
Daniel Chartier

dchartier said:

Hello Mustafa;
The terminologies "sourcing" and "sinking" apply to the status and wiring of digital inputs and outputs.
The following FAQ form Siemens might give you insights into the distinctions:
http://support.automation.siemens.com/WW/view/en/23451499
So if you are connecting between the PLC and the servo using digital signals you might have to refer to these definitions. If not, they are not applicable.
Hope this helps,
Daniel Chartier

Click to expand...

Here's another link for you.

http://www.patchn.com/index.php?option=com_content&task=view&id=57&Itemid=74

metwally.mustafa said:

thank you Mr.Mickey
and thank you Mr.Dchartier

Click to expand...

Your welcome

Hello, if you don't mind I would like to ask another question about source and sink. I'm trying to understand how that applies to VFD's that are switchable, would you always want to use sinking?
Thanks,
Jeff

peoplehouse said:

Hello, if you don't mind I would like to ask another question about source and sink. I'm trying to understand how that applies to VFD's that are switchable, would you always want to use sinking?
Thanks,
Jeff

Click to expand...

If you want to start/stop the VFD directly from the PLC output, then you have to select the correct type of input in the VFD to match the PLC output (source or sink).

Thank you Nonuke but I'm totally missing something. I've looked at Mickey's link again and totally understand how that works with photo cells. I just don't get why we would set up a drive to source. I've got some research to do.
Thanks again
Jeff

In my experience most places source because someone can (want) take a volt meter and look for power. Guess there Ohms position don't work. I always buy and use source I/O just for maintenance peoples. Every VFD I have used can source or sink. If it is just the VFD and a push button I stick with the sink option. (if you link the commons of 1 VFD you can source from the +VDC of 1 VFD) When its part of a system and you are linking them many all together with your common. I source. I think Europe is big on sinking and I would like to do that also.

I have been installing a new system 12 hours + day 10.
I think I didn't answer the question.

peoplehouse said:

Thank you Nonuke but I'm totally missing something. I've looked at Mickey's link again and totally understand how that works with photo cells. I just don't get why we would set up a drive to source. I've got some research to do.
Thanks again
Jeff

Click to expand...

If your PLC Output was a Sourcing type. Lets say 24VDC Sourcing, which is common. You would have to set your VFD Inputs to Sinking. If your PLC Output was a Sinking type, you would have to set your VFD Inputs to Sourcing.

Sourcing Outputs pull the voltage up to the Output Card Supply Positive Voltage (V+). Sinking Outputs pull the Output Voltage to the Output Card Supply Common or Negative (V-).

Sinking Inputs expect a Positive Input Voltage, and the Inputs Common Rail is connected to V-. Sourcing Inputs expect to be pulled to Common (V-), and the Inputs Common is connected to V+.

The most common in my experience is Sourcing Outputs and Sinking Inputs. I only use Sinking Outputs, or Sourcing Inputs, when I have no other choice due to the equipment I have to connect to.

There is usually a diagram in the VFD Manual showing the typical configuration. It basically consists of an Optoisolator for each Input with one side connected to the Input Terminal, and the other side connected to the Common Rail. Many VFDs will allow you to user either Sourcing or Sinking depending wether you connect V+ (Sourcing Input from Sinking PLC Output) or V- (Sinking Input from Sourcing PLC Output) to the Common Rail. The V+ or V- connection to the Common Rail insures that Current flows in the correct direction through the Optoisolators internal LED.

If you connect a VFD's Inputs directly to a PLC or other device. There is usually a jumper to the VFD's Internal Supply for use with Push Buttons, or Volts Free Contacts. This should be removed when the VFD is used with a PLC etc. This should be documented in the VFD's Manual.

I hope that helps clear it up some.

Stu......

Perhaps a simple sketch will help

[img=http://img407.imageshack.us/img407/949/0905001.th.jpg]

Good idea Roy, this is one that I grabbed out of a VFD PDF Manual. Unfortunately, I didn't have it handy last night. You can see the Common Rail for all the Inputs, the two opposite Polarity LEDs with Current Limiting Resistor, and the Factory Installed Jumper.
The second image shows the connections if you are going to use external control.

Stu.....