Mesa 7i96 Output Wiring

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20 Aug 2020 16:14 #178837 by xnaron
Replied by xnaron on topic Mesa 7i96 Output Wiring
The relays on those boards are electromechanical with coils. They are optically isolated so I don't think a flyback diode would be required but I wanted to confirm.

The relays are for future expansion in case I need to switch >2A and >36VDC and/or an inductive load. May never get used but they are there if I need them. :)

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20 Aug 2020 18:05 - 20 Aug 2020 18:08 #178848 by AgentWD40
Replied by AgentWD40 on topic Mesa 7i96 Output Wiring

Also I don't understand why you would bother with relay boards when the 7i96 has relays built into the outputs.


Probably because of all the conflicting advice out there! Has the general consensus change that a relay here truly isn't necessary for switching something like a plasma torch?
forum.linuxcnc.org/27-driver-boards/3659...6-and-thcad?start=10

For the sake of completeness I would like to add to this thread that PCW also recommends the current should be limited to 2-5A at each output relay, so if your PSU is larger than that you should put a fuse on the output circuit.
forum.linuxcnc.org/27-driver-boards/3981...output-fuse-s#178843

Also for completeness, I'd also like to know if these relay modules boards require a flyback diode.
Last edit: 20 Aug 2020 18:08 by AgentWD40.

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20 Aug 2020 20:11 #178864 by rodw
Replied by rodw on topic Mesa 7i96 Output Wiring
It looks like you have one guy recommending the use of relays. Its pretty clear in the manual
Six 36V 2A isolated outputs allow sinking, sourcing combinations of both.
So they can switch up to 36V 2 amps. I think you need to get the polarity right being SSR's
There is nothing on a plasma machine that needs 2 amps. Just check what is said about the voltage in the torch on signal for your machine to be safe.

With Hypersensing, the only output required is the torch on relay.

But yes if the relay has a coil, add the flyback diode. It won't do any harm. I did not do this initially on my 7i76e switching panel relays and it all survived but subsequently added them after reading comments by PCW. Just a IN4001-4007 or similar. Maybe your relay board does not need it but the Mesa card costs a lot more than it!

Now I've replaced my torch on relay with a SSR, I don't use any flybacks.

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