Here is how smema works: Machine A has a board to give to machine B. Machine A has an opto or a relay that will turn on or close when it is ready to pass this board to machine B. This is the "board available from previous" signal, telling machine B, "Hey, I have a board for you when your ready for it!".
How it works is inside machine B is an input with a pullup resistor on it. This signal is tied to the opto or the relay of machine A. When this opto or relay turns on or closes, it provides the signal back to machine B where it is tied to ground, and the signal goes low. So the "board available from previous" input on machine B goes low telling machine B there is a board available when it wants it.
Machine B tells machine A to send it the board with a copy of the same circuit except that machine B has the opto or the relay. This is the "machine ready from next" signal. Machine B thus finishes up what its doing with the board it has, gets rid of that board, and then looks at it's "board available from previous" input. Seeing that machine A has a board for it, it turns on the opto or toggles its relay thus returning the "machine ready from next" signal back to machine A telling machine A, "I'm ready for that board now, send it over!". Machine A then transfers the board to machine B, which turns off its opto or opens its relay to tell machine A that it has the board. Machine A then turns off it's opto or opens its relay to tell machine B that it no longer has a board to give to machine B.
Here is my problem: The opto has a diode across it to protect it and if machine A's wires are mixed up, machine A "board available from previous" signal will be at the anode of the diode which will always conduct and will pass the signal back to machine A where it will be pulled low. The result of this is the conveyor (machine A) will try and feed a board to machine B when machine B is not ready. Since the manufacturer of machine A uses relays the wires to his relay can be swapped as the relay will open and current will not flow regardless of direction.
My delema is the manufacturer of machine A is using a relay and just wants to get the product out the door to as many customers as possible. He doesn't care if his "board ready from previous signal" and return wires are mixed up because he has interperated SMEMA standard 1.2 to allow for this. He says that the manufacturer of machine B should do what he does and get rid of that opto and stick in a relay.
In respect for all the machine B manufacturers out there I want to prove him wrong. I have SMEMA Electrical Equipment Interface Standard 1.2 which on page 2 figure 1 vagely labels the signal lines. Can anyone out there say "Yes your right, stick to your guns and call him back.", or do I get the pin extraction tool and quietly swap the wires and say nothing?
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