What is a Test Output on a Safety Relay?

[Bbarnett]

I'm looking to use a Guardmaster Safety Relay from Allen Bradley. Its redundant input will be from the output of a GuardLogix PLC. That will work, right?

What's throwing me off is that the example connection diagrams for the Safety Relay show Estops connected to the Test Output which pulses. That's making me think that the safety input is looking for a pulsed signal.

Can somebody shed some light?

[sparkie]

What specific safety relay are you using? These things can be tricky, we have them on our saws at work. They can go FM on us sometimes.

[Donnchadh]

Hi

Sorry to ask but if you have a guard logix plc what is the need for a safety relay?
Would you not wire the items into the guard logix ?

Donnchadh

[Bbarnett]

Sparkie - None yet. I am thinking about ordering one if it is needed.

Donnchadh - That's what's racking my brain about this. The robot controller has a fence circuit that is currently being jumpered. Basically it has a +24V terminal that goes into a +IN terminal and a 0V terminal that goes into a -IN terminal. The GuardLogix gives me 2 redundant outputs.

I can only imagine that those two outputs with energize a coil that will open/close the contacts on the fence circuit.

We've used Interface Modules from Banner before, the IM-T-9A. I attached a schematic of that. I'm thinking that the GuardLogix only replaces the Primary Safety Device in that image. I am limited to only using Allen Bradley so that's why I can't just use the Banner Interface Module.

Can you think of a way around my thinking? Can I really just plug in the 4 wires from the fence circuit into the GuardLogix?

[dginbuffalo]

Not sure what flavor Guardmaster your using, but I believe you are correct-the test outputs (S11 S12?) pulse in different sequence. This is to check shorts to +DC and wire to wire shorts.

[James Mcquade]

Bbarnett,

if the robot circuit is jumpered meaning bypassed, then you should shut down the machine and fix the circuitry asap.

I don't know your system, but when you bypass a fence circuit guard on a robot, you are asking for trouble.

regards,
james

[Donnchadh]

Hi

You could use a set of safety contractors using the outputs from the guard logic
I would also wire a edm back to the guard logic

Donnchadh

[rigicon]

A test output on a safety relay is a pulse output every say 200 ms to check there is no frigs on the circuit. Frigs=engineering bypass. You can choose if this option is active or not. The pulse is usually superimposed on the + 24VDC line and is only of short generation.

[Bbarnett]

Thanks everyone for all the helpful replies. The cell is in the beginning stages of design so no worries about safety issues yet. The robot controller comes with the safety fence bypassed.

I think I finally understand what I need. I got the OK to use the Banner interface modules since I'm most familiar with them. I will use them for the fence circuit and tie in a positive feedback EDM through the contactors.