I am not in approvals, rather a designer of things (many of which have
been industrial). For safety you need an interlock which can easily be
accessed and stops the machine in a safe way. This switch should
interrupt power to the component, and should not depend on any other
circuitry.
There is a lot of sense to this -- who of us wants to trust our safety
to circuits and software? As an example, the FPGA doesn't load
correctly, the clock is lost (a common safety test), there is a
component failure, there is a connection failure. In industrial machines
this last is more common than we like.
Now if you are talking about an enable being complicated and depending
on many things that is OK. However, the circuit which is energized by
this complex logic needs to be disabled by a simple switch. So you could
have a relay that is powered by a chain of logic, one piece of which is
your interlock switch. All the logic needs to be true to enable, and any
of the logic could also disable. However, the interlock is in that
series chain and can also break current without any dependence on other
logic.
Curt
In real life:
Curt McNamara P.E. // senior electrical engineer
Logic Product Development
411 Washington Ave. N. Suite 400
Minneapolis, MN 55401
T // 612.436.5178
F // 612.672.9489
www.logicpd.com
Kunde, Brian wrote:
> I have limited experience working with industrial machines with moving
> parts so I would appreciate any help you can provide.
>
> To protect an operator from moving parts, my understanding is that I
> have to use an approved interlock device (in this case a switch) and it
> has to directly control the device that makes the motion (pneumatic
> solenoid).
>
> But on a future project, we would like to have the interlock switch talk
> to an FPGA (silicon) and have firmware and software controls the motion
> device after many sensor checks are made. These "checks" are quite
> complex where many things have to be just right in the right sequence
> for the motion to occur. Engineering is saying that the sequence is too
> complex to limit with a simple interlock switch system.
>
> Is it possible to use silicon chips, firmware, and software in such a
> circuit? Can such an approach be used and if so what is involved in
> qualifying it?
>
> Thanks,
> The Other Brian
>
>
>
>
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