dl205 module with voltage isolation

[Austin Mac Neil]

Hi

In general, and in particular, the d2-32nd3 sink/source input module from Direct Logic has four isolated commons. Does this mean I need 4 separate power supplies for this card?
And if anyone has a good answer as to why there are 4 commons on this card, I would really like to hear it.


Thanks

 

[bernie_carlton]

No, it just means that, in goups of eight, you can have sinking in one group and sourcing in another. Even with that you can have just one supply if it will handle it.

 

[Austin Mac Neil]

It is a sinking/sourcing input.
Are you suggesting that if a sink and source input are used in the same group with one common, it can cause problems?

 

[bernie_carlton]

One of the two won't work. Let's say that the common is tied to the minus side of the supply. The input pins, when nothing is connected are pulled low through th input circuitry. The inputs are off.

A sourcing input device will apply 24VDC to the input pin causing it to turn on.

A sinking input will apply common (minus side of the supply to the input doing nothing.

 

[Austin Mac Neil]

Logic check...

So in a sinking input module, a particular input is turned LOW to HIGH with 24vdc from an actuated PNP device.
A sourcing input module has a particular input turned HIGH to LOW with the 24vdc being loaded onto the actuated NPN device.

 

[bernie_carlton]

That sounds good. Refer to pages 2-16, 2-17 of the DL-205 User Manual.

Page 2-31 shows your module though it shows all 4 groups wire as 'sinking' inputs with the field devices switching the +24VDC side of the supply to the input pins.

Any of the groups can have the common attached to the +24VDC side of the supply and the input devices will switch the low (common) side of the supply to the input pins.

You just cant mix them within a group. It won't blow things up, it just won't work.

 

[Austin Mac Neil]

Thanks.