Why I need a vacation. . .
Archiver
Posts: 46,084
Group:
I'm having an interesting problem. My company makes an aerosol
collector that runs off of a stamp II. Until recently, they worked
fine, but now we've found something that has us all beat.
We have a DB9 connector soldered to the board just like the manual
says. The outside of the connector looks like brass, and is isolated
from the rest of the unit (including all the wires soldered to it).
However, when we touch the brass piece with a piece of wire, the
entire unit shuts off and goes through it's reboot cycle, like the
stamp had shut off. The wierd thing is, we also don't have the wire
connected to anything else. So, one isolated wire + one isolated
connector = reset stamp.
I'm having a hard time understanding this. I can't find any
measureable resistance between the connector's outside and any other
part of the circuit. I've got some pictures of our setup that I
could post to the group, if that would help.
Chris Moler
Design Engineer
MesoSystems Technology
www.MesoSystems.com
I'm having an interesting problem. My company makes an aerosol
collector that runs off of a stamp II. Until recently, they worked
fine, but now we've found something that has us all beat.
We have a DB9 connector soldered to the board just like the manual
says. The outside of the connector looks like brass, and is isolated
from the rest of the unit (including all the wires soldered to it).
However, when we touch the brass piece with a piece of wire, the
entire unit shuts off and goes through it's reboot cycle, like the
stamp had shut off. The wierd thing is, we also don't have the wire
connected to anything else. So, one isolated wire + one isolated
connector = reset stamp.
I'm having a hard time understanding this. I can't find any
measureable resistance between the connector's outside and any other
part of the circuit. I've got some pictures of our setup that I
could post to the group, if that would help.
Chris Moler
Design Engineer
MesoSystems Technology
www.MesoSystems.com
Comments
ACJacques
Chris Moler wrote:
>
> Group:
>
> I'm having an interesting problem. My company makes an aerosol
> collector that runs off of a stamp II. Until recently, they worked
> fine, but now we've found something that has us all beat.
>
> We have a DB9 connector soldered to the board just like the manual
> says. The outside of the connector looks like brass, and is isolated
> from the rest of the unit (including all the wires soldered to it).
> However, when we touch the brass piece with a piece of wire, the
> entire unit shuts off and goes through it's reboot cycle, like the
> stamp had shut off. The wierd thing is, we also don't have the wire
> connected to anything else. So, one isolated wire + one isolated
> connector = reset stamp.
>
> I'm having a hard time understanding this. I can't find any
> measureable resistance between the connector's outside and any other
> part of the circuit. I've got some pictures of our setup that I
> could post to the group, if that would help.
>
> Chris Moler
> Design Engineer
> MesoSystems Technology
> www.MesoSystems.com
I would suspect the "ATN" pin. The ATN line on the BS2 can behave like an
antenna. It resets the stamp whenever a spike of 1.4 volts (or greater) appears
on it. Even a short length of wire (the trace
on the PCB) attached to the ATN pin can pick up this level of induced RF
noise (your piece of wire can be coupling RF noise in the room (fluorescent
lights are notorious) to the ATN pin, without a physical connection)! The ATN
line is connected to the base of a transistor, so when ATN is above
1.4 volts (and essentially NO current required) the transistor turns on,
which pulls the RESET pin to ground (Vss) and resets the stamp. (Refer to
figure H-1 in the Parallax Manual Version 1.9 for a schematic of the BS2,
and you'll see how this is happening). I've made it a habit to install a 1 K
resistor from the ATN pin to ground
(Vss) (between BS2 pins 3 & 4) in all of my stamp projects. This keeps the
ATN line from floating too high above ground. Don't worry, this won't effect
or damage your computer's serial port when you are programming the BS2.
Jim Howard
Effects Engineer
Imaging & Effects
Walt Disney Imagineering
>
> From: Chris Moler
> Reply To: basicstamps@egroups.com
> Sent: Wednesday, June 21, 2000 4:36 pm
> To: basicstamps@egroups.com
> Subject: [noparse][[/noparse]basicstamps] Why I need a vacation. . .
>
> Group:
>
> I'm having an interesting problem. My company makes an aerosol
> collector that runs off of a stamp II. Until recently, they worked
> fine, but now we've found something that has us all beat.
>
> We have a DB9 connector soldered to the board just like the manual
> says. The outside of the connector looks like brass, and is isolated
> from the rest of the unit (including all the wires soldered to it).
> However, when we touch the brass piece with a piece of wire, the
> entire unit shuts off and goes through it's reboot cycle, like the
> stamp had shut off. The wierd thing is, we also don't have the wire
> connected to anything else. So, one isolated wire + one isolated
> connector = reset stamp.
>
> I'm having a hard time understanding this. I can't find any
> measureable resistance between the connector's outside and any other
> part of the circuit. I've got some pictures of our setup that I
> could post to the group, if that would help.
>
>
> Chris Moler
> Design Engineer
> MesoSystems Technology
> www.MesoSystems.com
>
>
>
>
>
one solenoid pump and several solenoid valves. You can just see the
circuit board under the valve backing plate. The housing is ABS with
rubber gaskets. In the first picture, you can also see the brushless
motor controller to the side, next to the valve back plate. We're
running with one 12VDC lead acid battery. If you need any more info,
I'd be happy to share with you.
Thanks
Chris
--- In basicstamps@egroups.com, "A.C.Jacques" <acjacques@i...> wrote:
> Very strange. Please send me the photos.
> ACJacques
>
> Chris Moler wrote:
> >
> > Group:
> >
> > I'm having an interesting problem. My company makes an aerosol
> > collector that runs off of a stamp II. Until recently, they
worked
> > fine, but now we've found something that has us all beat.
> >
> > We have a DB9 connector soldered to the board just like the manual
> > says. The outside of the connector looks like brass, and is
isolated
> > from the rest of the unit (including all the wires soldered to
it).
> > However, when we touch the brass piece with a piece of wire, the
> > entire unit shuts off and goes through it's reboot cycle, like the
> > stamp had shut off. The wierd thing is, we also don't have the
wire
> > connected to anything else. So, one isolated wire + one isolated
> > connector = reset stamp.
> >
> > I'm having a hard time understanding this. I can't find any
> > measureable resistance between the connector's outside and any
other
> > part of the circuit. I've got some pictures of our setup that I
> > could post to the group, if that would help.
> >
> > Chris Moler
> > Design Engineer
> > MesoSystems Technology
> > www.MesoSystems.com
unused inputs to their inactive state, usually ground, through a suitable
resistor, something on the order of 1K to 4.7K. Probably be a good idea
to tie the body of your DB9 to ground too. If it still happens try
running a suitable resistor to each of the DB9 lines. Is the ground of
your system tied to earth?
On Wed, 21 Jun 2000 23:36:52 -0000 "Chris Moler" <cmoler@m...>
writes:
> Group:
>
> I'm having an interesting problem. My company makes an aerosol
> collector that runs off of a stamp II. Until recently, they worked
> fine, but now we've found something that has us all beat.
>
> We have a DB9 connector soldered to the board just like the manual
> says. The outside of the connector looks like brass, and is
> isolated
> from the rest of the unit (including all the wires soldered to it).
>
> However, when we touch the brass piece with a piece of wire, the
> entire unit shuts off and goes through it's reboot cycle, like the
> stamp had shut off. The wierd thing is, we also don't have the wire
>
> connected to anything else. So, one isolated wire + one isolated
> connector = reset stamp.
>
> I'm having a hard time understanding this. I can't find any
> measureable resistance between the connector's outside and any other
>
> part of the circuit. I've got some pictures of our setup that I
> could post to the group, if that would help.
>
>
> Chris Moler
> Design Engineer
> MesoSystems Technology
> www.MesoSystems.com
>
>
>
>
>
________________________________________________________________
YOU'RE PAYING TOO MUCH FOR THE INTERNET!
Juno now offers FREE Internet Access!
Try it today - there's no risk! For your FREE software, visit:
http://dl.www.juno.com/get/tagj.
I had a similar problem touching a Stamp circuit after standing up from my
chair. It was caused by an ESD spark. Possibly ESD or a strong local radio
station pickup (or other noise sources) could do the same thing to your
setup. It would seem good practice to have the connector shell grounded to
your circuit common, and maybe also to earth ground, if available. Does
your cable have a shield? If so, it should be connected to the DB shell.
Ray McArthur
> I'm having an interesting problem. My company makes an aerosol
> collector that runs off of a stamp II. Until recently, they worked
> fine, but now we've found something that has us all beat.
>
> We have a DB9 connector soldered to the board just like the manual
> says. The outside of the connector looks like brass, and is isolated
> from the rest of the unit (including all the wires soldered to it).
> However, when we touch the brass piece with a piece of wire, the
> entire unit shuts off and goes through it's reboot cycle, like the
> stamp had shut off. The wierd thing is, we also don't have the wire
> connected to anything else. So, one isolated wire + one isolated
> connector = reset stamp.
>
> I'm having a hard time understanding this. I can't find any
> measureable resistance between the connector's outside and any other
> part of the circuit. I've got some pictures of our setup that I
> could post to the group, if that would help.
>
> Group:
>
> I'm having an interesting problem. My company makes an aerosol
> collector that runs off of a stamp II. Until recently, they worked
> fine, but now we've found something that has us all beat.
>
> We have a DB9 connector soldered to the board just like the manual
> says. The outside of the connector looks like brass, and is isolated
> from the rest of the unit (including all the wires soldered to it).
> However, when we touch the brass piece with a piece of wire, the
> entire unit shuts off and goes through it's reboot cycle, like the
> stamp had shut off. The wierd thing is, we also don't have the wire
> connected to anything else.
Is there a pre-manufactured or static-shieled (EMI, etc) cable being
connected ? If so, the "short" may be ground looping through the "far"
end via the drain shield or the plastic connector hood. The resistance
is too small to measure with ordinary equipment, yet provides a
sufficient ground path to reset the Stamp. If ATN is brought low, the
Stamp will reset. So too, if V+ drops even momentarily below the
brown-out voltage, a reset will occur.
> So, one isolated wire + one isolated
> connector = reset stamp.
>
> I'm having a hard time understanding this. I can't find any
> measureable resistance between the connector's outside and any other
> part of the circuit. I've got some pictures of our setup that I
> could post to the group, if that would help.
>
> Chris Moler
> Design Engineer
> MesoSystems Technology
> www.MesoSystems.com
re-set the stamp.
Norm & Monda
Cozy MK IV #202
Ford V-6 Powered
Original Message
From: "Chris Moler" <cmoler@m...>
To: <basicstamps@egroups.com>
Sent: Wednesday, June 21, 2000 7:36 PM
Subject: [noparse][[/noparse]basicstamps] Why I need a vacation. . .
> Group:
>
> I'm having an interesting problem. My company makes an aerosol
> collector that runs off of a stamp II. Until recently, they worked
> fine, but now we've found something that has us all beat.
>
> We have a DB9 connector soldered to the board just like the manual
> says. The outside of the connector looks like brass, and is isolated
> from the rest of the unit (including all the wires soldered to it).
> However, when we touch the brass piece with a piece of wire, the
> entire unit shuts off and goes through it's reboot cycle, like the
> stamp had shut off. The wierd thing is, we also don't have the wire
> connected to anything else. So, one isolated wire + one isolated
> connector = reset stamp.
>
> I'm having a hard time understanding this. I can't find any
> measureable resistance between the connector's outside and any other
> part of the circuit. I've got some pictures of our setup that I
> could post to the group, if that would help.
>
>
> Chris Moler
> Design Engineer
> MesoSystems Technology
> www.MesoSystems.com
>
>
>
>
>
>
responses were informative and extremely helpful. I only hope I can
return the favor someday...
Thanks again,
Chris
--- In basicstamps@egroups.com, "Chris Moler" <cmoler@m...> wrote:
> Group:
>
> I'm having an interesting problem. My company makes an aerosol
> collector that runs off of a stamp II. Until recently, they worked
> fine, but now we've found something that has us all beat.
>
> We have a DB9 connector soldered to the board just like the manual
> says. The outside of the connector looks like brass, and is
isolated
> from the rest of the unit (including all the wires soldered to
it).
> However, when we touch the brass piece with a piece of wire, the
> entire unit shuts off and goes through it's reboot cycle, like the
> stamp had shut off. The wierd thing is, we also don't have the
wire
> connected to anything else. So, one isolated wire + one isolated
> connector = reset stamp.
>
> I'm having a hard time understanding this. I can't find any
> measureable resistance between the connector's outside and any
other
> part of the circuit. I've got some pictures of our setup that I
> could post to the group, if that would help.
>
>
> Chris Moler
> Design Engineer
> MesoSystems Technology
> www.MesoSystems.com