SMEMA Interface minimum requirements

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Hi all. We are currently trying to build a downstream bypass... - Oct 18, 2019 by kyleh04

Show this drawing because we know nothing. At the end I put ... - Oct 21, 2019 by Michał

Sure thing. They are attached. ... - Oct 21, 2019 by kyleh04

As you can see in machine B on pins 1-2, the circuit closes ... - Oct 21, 2019 by Michał

I haven't thought about this in a while, wrote up something ... - Oct 21, 2019 by Dilbert

kyleh04

#83605

SMEMA Interface minimum requirements | 18 October, 2019

Hi all. We are currently trying to build a downstream bypass to have our final conveyor feed into our oven, which doesn't have a SMEMA interface. Right now we have to manually connect the two downstream ready pins by hand. I have a good idea of how I want to build this circuit, but I am confused by one spec in the interface standard:

"These signals are shown in Figure 2, and may be obtained using an optical isolator or a relay. The minimum requirements are to switch 3OV, 10 mA. At 10 mA, the output "LOW" must not exceed 0.8 volts."

What is it referring to by "At 10 mA, the output "LOW" must not exceed 0.8 volts."

The other parts are really straightforward, but I can't figure out what it is talking about exceeding 0.8V..

Thanks for any advice.

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Michał

#83625

SMEMA Interface minimum requirements | 21 October, 2019

Show this drawing because we know nothing. At the end I put on the button - downstream is a "closed contact" signal.

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kyleh04

#83626

SMEMA Interface minimum requirements | 21 October, 2019

Sure thing. They are attached.

Attachments:

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Michał

#83627

SMEMA Interface minimum requirements | 21 October, 2019

As you can see in machine B on pins 1-2, the circuit closes - give the button / contact here. The voltage you provide most likely applies to pins 3-4. In my (and in the SMEMA standard) it looks like this:

Attachments:

2019-10-21_211325.png

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Dilbert

#83628

SMEMA Interface minimum requirements | 21 October, 2019

I haven't thought about this in a while, wrote up something on how this works here years ago. I think I remember.....

As you know the first machine finishes the board and is "ready to send". It tells the second machine this by connecting pins 3 & 4 either through an output relay contact or an optocoupler. You don't have to worry about this set of pins, Your second machine is "dumb" and is not looking at this signal.

The second machine (oven) tells the first machine (conveyor) it's busy by leaving its output pins 1 & 2 open. Pins 1 & 2 are an output from the second machine and an input to the first machine and there is a voltage present of 30v to (I think) around 2.5vdc depending on how the conveyor manufacturer built his machine. This voltage level is present at the input of the first machine (conveyor) and must be pulled low by the output of the second machine (oven) to tell the first it is ready to receive a board. When the second machine is ready it connects pins 1 & 2 through an output relay contact or an optocoupler and it's output must drop from a max of 30vdc to .8v or less and be able to handle a max current of 10mA. That's what it means.

So as the guy above said, all you have to do is short pins 1 & 2 at the first machine (conveyor) and it'll feed boards to the oven with out being told to.

Thanks for the memories!

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