Re: Inside the X endstop cable

[Jetguy]

I've covered this before. A suggested fix is to just disconnect the 5
volt wire at the motherboard and NOT send 5 volts to the endstops
which do not need it for normal operation. The only purpose that wire
has is to make the LED light up when the switch it hit. The
motherboard is sensing when the sense wire is grounded, not connected
to 5 volts ever.

The white wire (the wire closest to the edge of the mainboard with the
screw contacts in each 4 pin endstop connector) is the 5 volt wire and
a paperclip can be used to push on the tiny metal tab inside and slide
the metal wire and connector out of the shell. Just tape off the white
wires with electrical tape by folding them back along the length of
the wire.

Prevention, prevention, prevention!!!
http://www.thingiverse.com/thing:38045

On Jan 27, 3:04 pm, Luciano <galassi...@gmail.com> wrote:
> Hi,
> one week ago I toasted the mightyboard of my replicator1 exactly at the end
> of a print. The 5V voltage regulator burnt.
> The Makerbot guys sent me a new mightyboard and a new Xendstop cable so I
> cut the external insulation of the old one.
> I think that the attached picture clearly explain what happened (a short
> between the red wire and the external one / black one).
> Is there anyone that could suggest a solution for this kind of problem ?
> Where can I put a fuse ?
> Does anyone know about any better cables?
> I bought the Replicator in November and I have printed for no more than 30
> hours before the board failure.
> I would like to avoid this problem in the future.
> Thanks
>
> Luciano
>
>  Xendstop.JPG
> 90KViewDownload

[Jetguy]

covered in the board failure thread:
http://groups.google.com/group/makerbot/browse_thread/thread/6e81b02d68add91d/6f4093887d64b7e2?lnk=gst&q=white+wire#6f4093887d64b7e2

> > 90KViewDownload- Hide quoted text -
>
> - Show quoted text -

[Mark Cohen]

You are the first person i know to truly have this problem. I thought it was all bs when my mobo blew. I replaced the cable anyway.

On Jan 28, 2013 8:58 AM, "Luciano" <galas...@gmail.com> wrote:

Hi,
one week ago I toasted the mightyboard of my replicator1 exactly at the end of a print. The 5V voltage regulator burnt.
The Makerbot guys sent me a new mightyboard and a new Xendstop cable so I cut the external insulation of the old one.
I think that the attached picture clearly explain what happened (a short between the red wire and the external one / black one).
Is there anyone that could suggest a solution for this kind of problem ?
Where can I put a fuse ?
Does anyone know about any better cables?
I bought the Replicator in November and I have printed for no more than 30 hours before the board failure.
I would like to avoid this problem in the future.
Thanks

Luciano

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[Jetguy]

Woah, this doesn't make sense and I should have seen it . The RED wire
is NOT 5 volts, the white wire is. The red wire is the sense pin
directly to the mega1280 pin. Now, the Red wire would have the
internal pullup resistor so no way would it be able to source enough
current to burn the the end. Both the original cables and the
replacement had the exact same wire color and order.

Either, this was a picture of a non-stock or alternate cable we aren't
aware of, or the impossible just happened and a pin on a mega 2560 put
out enough current to burn the contact point where the wire broke. I'm
not accusing anything here, just saying the OP had better check the
colors and wire situation with the new board.

This is why I described both the position and the wire color in the
method to not send 5 volts to the endstops. That way, if someone did
have non-standard cables, they could still figure it out.

On Jan 28, 8:23 pm, Mark Cohen <markcoh...@gmail.com> wrote:
> You are the first person i know to truly have this problem. I thought it
> was all bs when my mobo blew. I replaced the cable anyway.

> On Jan 28, 2013 8:58 AM, "Luciano" <galassi...@gmail.com> wrote:
>
>
>
> > Hi,
> > one week ago I toasted the mightyboard of my replicator1 exactly at the
> > end of a print. The 5V voltage regulator burnt.
> > The Makerbot guys sent me a new mightyboard and a new Xendstop cable so I
> > cut the external insulation of the old one.
> > I think that the attached picture clearly explain what happened (a short
> > between the red wire and the external one / black one).
> > Is there anyone that could suggest a solution for this kind of problem ?
> > Where can I put a fuse ?
> > Does anyone know about any better cables?
> > I bought the Replicator in November and I have printed for no more than 30
> > hours before the board failure.
> > I would like to avoid this problem in the future.
> > Thanks
>
> > Luciano
>
> >  --
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[Jetguy]

That red wire in all the cables I have seen could either touch ground
or 5 volts and not even arc, so the fact it is burned is disturbing.
Again, it's should be connected to the sense pin, and that pin has a
pullup resistor of several K ohms and is fed 5 volts, so a short (the
same thing the switch does) to ground wouldn't draw but a few mA at
best. Shorting it to 5 volts would pass zero current, 5 volts is at
the same potential at both ends. The only failure mode that would
cause what is shown in the picture is that cable being wired a
different scheme from every other cable out there. It's possible, so
my reason for bringing this to question is to find out how many people
might have similiarly wired cables? Makes troubleshooting hard if I
call out wire colors and they aren't a standard.

The new mystery of the week?

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[Bottleworks]

I like this idea of disconnecting the 5 volt feed.  OTOH, what about fusing it?  100mA do?  Too much, too little? 
http://www.digikey.com/product-detail/en/37001000000/F5466CT-ND/3306856

What about fusing all 3 wires?

[Bottleworks]

No comment on using fuses?

[Gary Crowell]

Well, if one had to have LED's at the switches, a good compromise might be to have the LED series resistors on the 5V side and placed on the controller board rather than at the switch board.  Size the resistors so they could handle a short-to-ground current.  Then there'd be no fuse to replace.  Indication of failure is that the LED doesn't work - no smoke.  A few ma increase load on the regulator, which shouldn't be a problem (in a normal system - not sure about this one).

Gary

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[Bradley Pearce]

That's a great idea!

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[Jetguy]

The reason why I didn't comment is, in theory no more than 50mA ever
is required on a given endstop. It's just an LED than maybe needs
10mA. A fuse rated at 100mA might not blow until 500mA. This was true
to the chemical one I used in my mod rated at 5A but trip was 10A!
The regulator is rated at 5A, and, from what we gather from the way it
blows, an absolute max instantaneous rating.

What I'm saying is I don't know that a fuse will protect the circuit.
Certainly prevention, but not an outright foolproof fix.
Rather than say, yes that will work, I was going to let others chime
in.

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[Luciano]

Hi
I feel a bit confused. The wiring scheme of the X endstop cable looks OK and it's the same as the new one (now the yellow wire is black but it's the only difference).
I'm not skilled in electronics and I thought that the red wire was the +5V, but I agree with you that if it is the sense one is not easy to explain why it looks burned.
Consider that I re-checked the white one and I can't see any problem on it (I can't see any wear and the conductivity is ok).

Anyway I wonder if it is really necessary a coaxial cable with an external metallic shield.This increases the chances of a short.
You suggested to disconnect the white wire. I think that I can use it for the ground putting it in place of the black one.
What do you think about it?

Thank you for your patience. And sorry for my english !

[Jetguy]

No, you do not want to do that and you want the shielding. The sense
pin directly goes to the mega1280 (AKA main chip). So that long
endstop wire acts like an antenna and any EMI RFI from the power
supply, motors, a nearby cell phone, could be picked up and shot
directly into the processor causing a glitch or print failure. The
metal shield being grounded in the cable prevents the inner wires from
acting like the antenna.

Also, the wire colors meant nothing. MakerBot used off the shelf
cables in a non-standard application. Never ever assume a wire color
means something.

And that said, that's why I specifically gave both the color and pin
location to identify the 5 volt pins which is white in your picture
and to the left.

The following preventions may be effective:
You can remove it from the plug (removes all chances of the short
blowing the regulator bus does disable the led on the endstop)

Put a fuse inline with the wire ( gives more failure points since you
cut and spliced the wire, possible short, and may not blow fast enough
to provide protection depending on the smallest fuse you can find).

Put a resistor in line around 1k ( the problem is, if you go a lower
value, then the short current would be higher and may still blow the
regulator, but then this 1k may not be enough to barely light the LED.
You are also splicing the wire and more possible short points).

Removing the wire from the shell is the simplest, it is reversable,
and completely removes the issue of shorting. At worst, if it shorts
again, the endstop simply doesn't work and you'll know it during the
print.

>  Xendstop2.jpg
> 254KViewDownload