Is using a relay necessary in this case?

[floppy32]

In the following diagram, an interlock terminal and an LED will be mounted on enclosure. Inside the enclosure there is an 12V 10A SMPS power supply, a laser module(draws 6A at 12V) and some digital electronics which powers off the laser via relay in case of open interlock or any other logic low input(such as temperature ok ect):

Diagram1

But in my case, I now actually need only the interlock to activate/deactivate the power to the laser module and need to be safe. So I decided to use the PSU ground as interlock terminal(to expose person to safe voltage level) and discarded the relay as follows:

Diagram2

Interlock terminal will be accessible to a user to use his own button or circuit.

So my question is about Diagram2: Is it fine to leave the interlock terminal this way without any relay? And is there any benefit to isolate the control and the power circuitry by using a relay?

 

[barry]

Wow, you sure made that schematic a lot harder to read than it had to be.

I don't know why you're concerned about exposing people to "safe voltage". 12V is intrinsically safe. But, just for future reference, you haven't protected anyone from "unsafe voltage" just because you've got ground on the connector. When the interlock is open, you'll have 12V at the bottom terminal. (Or, 1000V, if that's what your supply is).

 

[floppy32]

Wow, you sure made that schematic a lot harder to read than it had to be.

I don't know why you're concerned about exposing people to "safe voltage". 12V is intrinsically safe. But, just for future reference, you haven't protected anyone from "unsafe voltage" just because you've got ground on the connector. When the interlock is open, you'll have 12V at the bottom terminal. (Or, 1000V, if that's what your supply is).

Sorry you are correct 12V harmless. But isnt using a relay good to prevent bouncing for the interlock and isolate the DC power from control(interlock) terminals?

 

[KlausST]

Hi,

A relay contact will bounce....so what bouncing do you prevent?
Is isolation necessary?

Klaus