Sinking/Sourcing Input Outputs

[luisarcher]

Hello again guys,

I've read tons of informations on sinking and sourcing inputs and outputs, however there is something bugging me with this.

I want to connect a Banner TowerLight to my PLC to light its light (fun incomming). Here is an image of the wires:


I have my output card, which is a SOURCING one. Therefore, I know that my output card will send current to the towerlight to light its light. So, I think that I should go with the sinking connection, so NPN.

However, I check the picture and I don't understand how it works. I will connect my pin 3 to my 24 VDC and the rest of the colors (pin 4-1-2-5) will be connected to the PLC outputs. So, when I will activate my output, it will send current to the colors but where will that current sink if my blue cable (pin 3) is connected to the 24 VDC ? Shouldn't it be connected to the ground ?

Thanks a lot,
luisarcher.

 

[sigmadelta]

It's best to go by the wiring diagram of the Banner TowerLight, not this "NPN" diagram.

 

[luisarcher]

It's best to go by the wiring diagram of the Banner TowerLight, not this "NPN" diagram.

I took the picture from the Banner's Data Sheet

 

[Gomez_]

If your output card is SOURCING its providing a path to the + side, so you would use the PNP labeled diagram.

 

[sigmadelta]

If the common on your digital output card is minus (-), then use the PNP diagram.

 

[Gomez_]

If the common on your digital output card is minus (-), then use the PNP diagram.

uh, then both sides of the light would be connected to -

 

[sigmadelta]

If the common on the digital output card is -, then you are switching +

 

[luisarcher]

If your output card is SOURCING its providing a path to the + side, so you would use the PNP labeled diagram.

That was what I thought after thinking it for a bit, but I find it odd that Sourcing and PNP go together.

Thanks a lot guys !

 

[Gomez_]

If the common on the digital output card is -, then you are switching +

Ah right i was thinking of relay when you said common.

 

[jraef]

In reality if you look at that diagram, all it is telling you is that the lights don't really care which direction the flow goes. All it is saying is that whichever side is +, the other side is -. So whatever you use as the Common in your PLC output card gets connected to terminal 3, the individual outputs then go to the other terminals.

 

[John Morris]

I overthought this once too .

These lights are our standard light towers

Current is either going left to right, or right to left.

Hook wire three to your-24 on the power supply

Hook the positive +24 to the comm on the card and wire in you assigned outputs

Just think of it as a light switch. Right? All your doing is passing current.

 

[mellis]

The "problem" is the diagram is trying to be helpful and showing you how to wire to "sourcing" output and you are overthinking it. As most of the people here did, I usually just look for the common and that tells the story. "Sinking" and "Sourcing" are not all that helpful or intuitive to me.

 

[sigmadelta]

I'm having that sourcing feeling.... or is it that sinking feeling...

 

[Bit_Bucket_07]

I have my output card, which is a SOURCING one. Therefore, I know that my output card will send current to the towerlight to light its light.

You are unnecessarily confusing the issue by thinking in terms of "sending current" to the lamps. You will create current flow through the lamp when you apply a voltage to it, whether you use a sinking or sourcing output module. The only difference is whether you are doing the switching on the positive or negative side of the circuit.

Sourcing outputs unconditionally connect the negative side of the power supply to the load while switching the positive side. Sinking outputs unconditionally connect the positive side of the power supply to the load while switching the negative side.

There is some inherent confusion built into discussions of current flow because electronic drawings use symbols based upon "classic" current flow, which is from the positive to the negative side of the power supply, although we all know from basic physics classes that current actually flows through a load from the negative to the positive side of the power supply.

Unless, of course, you are discussing hole current within a transistor -- but that's another discussion altogether.

 

[Bit_Bucket_07]

uh, then both sides of the light would be connected to -

No it wouldn't.