Mechanical Endstop

Hello, I buy these endstops



When I go to connect I fail to make them work, and try all forms and does not recognize, but testing continuity with the multimeter I know these are working properly, Can anyone explain me the correct way to connect?, I have a RAMPS 1.4, arduino mega 2560 and Sprinter firmware, If anyone can help I would be very grateful, thank you very much and sorry for my bad english

Where did you buy them from? If an eBay seller, please link to them?

I ask because there has been a few clones that don't quite work properly.

A post that might prove useful is this one (the last post): [forums.reprap.org]

Edited 1 time(s). Last edit at 01/26/2014 12:54AM by Cefiar.

As far as I can tell, initial confusion in that thread was caused by assuming the Makerbot pinout has Pin 1 at the "top", in fact according to Makerbot schematic Pin 1 is at the "bottom" on their board, and this convention seems to have been reliably followed by all the clone boards as well. Although for some reason they like to remove legends from the silkscreen and wire cables with pin 1 in opposite place to normal convention.

Unfortunately concepts like "pin 1" and "top" and "bottom" are highly flexible, so we should never assume any orientation. There are some Molex connectors that have official drawings which show pin 1 location being in different places on the plug and receptacle in the same series. Obviously this is confusing, but the response from Molex was basically "it is up to the customer to designate circuit ordering". In some drawings I see they no longer call it pin 1, but something like "reference mark".

But anyway, if you have buzzed out the switch, or even powered from a battery and checked it is working, it is probably a configuration issue in the firmware. There are usually a generous number of options, you need to specify whether it is a min or max switch, enable internal pullups, probably enable "inverted endstop" since the signal is active when 0V.

Checking RAMPS-FD v2, I realize that we have adopted a PCB layout compatible with a 4 pin connector, but signals in different order. I wonder if it is a good idea to match the Makerbot pin out, as it seems to be the closest thing to a standard? There is still an issue with polarity, but at least you could make a straight 4 wire cable.

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Quote
bobc
Checking RAMPS-FD v2, I realize that we have adopted a PCB layout compatible with a 4 pin connector, but signals in different order. I wonder if it is a good idea to match the Makerbot pin out, as it seems to be the closest thing to a standard? There is still an issue with polarity, but at least you could make a straight 4 wire cable.

Bobc, just my 2cents, but i would make the pin out match optical endstops(and maybe they are the same and assuming there is a standard for them ) my assumtion is optical's will be more standard in the future.

Ha, good point

Makerbot pin outs are consistent between their opto endstops and mechanical endstops at least.

There are various versions using 3 pins with different pin outs, not much we can do about that.

So I will go ahead and make that change.

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can't you just look at the back of the board?
There is a clear track going from one of the pins to the item labeled common on the spring switch.
That one is signal I think. I can check when home tonight.
Then two middle are ground, and other is + VCC.

hello, thank you all for your support. With this picture I could solve the problem



Also had problems with sprinter but when I change it for marlin the problems disappeared

thank you very much

I am pretty sure that diagram is incorrect, so I would not advise anyone to follow it.

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Here are some pics of the sainsmart 4 pin board, showing tracks on front and back.
I wish I knew how to put the images inline in this msg, hate attachments.

Its an open source community. Download the source files, and open those, and see exactly which is what, beyond any doubt. Whats the point to discuss on drawings and images when source files should be up there. Just saying that if source files are not provided, then the item is not really open source, is it. And thats where the real problem lies. And hence a lesson to pay attention to this aspect next time you buy stuff in an open source community, check source files first, and if you cant find them then simply dont buy. And i dont say this to be mean, but it is just the truth as i see it, thats all.

NoobMan: While I definitely agree with what you say, I still see cheap sellers on eBay that do point to source. Unfortunately it's NOT the source of the product you're trying to buy from them. And if people have no idea at electronics, then they're not going to know better anyway.

NoobMan,
What do you do if you don't understand the implications of electronic schematics fully?
I'm not too bad either, I've studied lots of circuit tutorials but I am still a beginner.
Its tricky because here I am a specialist in CAD and CAD programming, but I don't know how to not fry my arduino without asking
Reality is, I did not think a switch would be so complex. Normally we just play to figure things out, but others got bit so now we ask questions like we know nothing.
Annoying I know, but there is a little Noob in all of us (Most have two...).

Quote
jmaeding
Here are some pics of the sainsmart 4 pin board, showing tracks on front and back.
I wish I knew how to put the images inline in this msg, hate attachments.

Looks like a "standard" Makerbot to me.

I realise that it is Makerbot who really screwed up here. They put the legend on the silkscreen underneath the connector, how dumb is that? Equally annoying is breaking the URLs on their website.

Anyway, I drew up a quick diagram which I think is correct...

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yah, that is different than the sketches by Ken. You have VCC on bottom pin, he had on top.
Hope that guy who said the sketch would help realizes this.

I would like to understand the function of the VCC for this board.
Is it to power the led's?
Maybe someone who gets the schematic at:
[forum.hobbycomponents.com]
can comment.

It powers the LED, and for whatever reason is also hooked to the other side of the switch (NC).

So the signal is +5V while the switch is not depressed, +5V while it switches (through pull-up resistor, as it's not connected to anything as it switches), and Gnd when the switch is depressed.

does that "whatever reason" make any sense? Is that what is burning boards?
Maybe opto stops would not do this, as they are variable resistors right? A switch is a strong short...

Not really. The problem is that you can invert the connector (by putting in a plug that doesn't have the locking/indexing part back-to-front), and you connect VCC to the signal pin (aka the switch).

At this point, when you press the switch together, you short VCC (which is on the Signal) to Ground.

There is no simple answer at this point. I convinced (and helped) bobc to change the layout on RAMPS-FD to mitigate this as much as possible for directly wiring up switches without PCB's on them (direct sire to the switches. Even then, with a switch on a PCB, if you make up a bad cable you're still going to short VCC to Gnd.

Probably the only way to avoid problems is to put a very small fuse (eg: 50-100mA) on either the endstop board, or on the electronics. You could put a small resistor in-line with the VCC (on the electronics) for switch endstops, but then you won't get full voltage to run an opto (not usually a problem) or a Hall-O (definitely a problem). You could put one in-line with the signal, but not sure how well that would work for normal conditions.

Re: Opto's/Hall-O's.

Correct. You will just most likely kill the Opto component/Hall effect chip if you get the wiring wrong. Specifically for that case, you need to get VCC and GND back to front, rather than VCC and Signal.

Edited 1 time(s). Last edit at 01/29/2014 05:19PM by Cefiar.

I did wonder about fitting current limit into the endstop VCC pins, in a way that doesn't interfere with opto/hall switches. Would require a little more space, and suitable part. There are some 0603 fuses, though how the user would replace them I'm not sure.

In the case of the Makerbot endstops, I think the mechanical endstops were designed to be drop in replacements for their optos, so VCC was already on the connector. They may also have not had pullups on the controller because they were designed for the optos.

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