bizarre problem w/ ground
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Posts: 46,084
hey everyone,
I'm having a bizarre problem with common ground between my basic
stamp and another device. I have a tcm2-50 electronic compass hooked
up to a wall-wart and there are two serial lines (transmit and
receive) between this compass and my bs2sx. My bs2sx is powred by a
seperate wall-wart. For some reason, when I connect the grounds of
the two devices, my computer says "hardware not found" when I try to
download to the stamp. However, without the common ground wire, my
computer downloads to the bs2sx just fine. However, the serial
connection between the stamp and the periferal device does not seem
to be working correctly, so I think that I do need the common ground
wire...... does anyone know what is going on? Thank you very much for
any help.
I'm having a bizarre problem with common ground between my basic
stamp and another device. I have a tcm2-50 electronic compass hooked
up to a wall-wart and there are two serial lines (transmit and
receive) between this compass and my bs2sx. My bs2sx is powred by a
seperate wall-wart. For some reason, when I connect the grounds of
the two devices, my computer says "hardware not found" when I try to
download to the stamp. However, without the common ground wire, my
computer downloads to the bs2sx just fine. However, the serial
connection between the stamp and the periferal device does not seem
to be working correctly, so I think that I do need the common ground
wire...... does anyone know what is going on? Thank you very much for
any help.
Comments
common. If you look at the main circuit breaker panel for your house, you'll
see three wires AND a ground going to it. Two are hot, one is common. Common
is just the AC line that is mid-potential beween the two hots. Ground to the
panel, not to earth.
The common wire is subject to the same sorts of ground loop problems that
you can experience in electronics. Although we call it ground, it can have a
positive or negative voltage potential relative to real ground. If you put a
volt meter between your two ground wires, dollars to donuts you'll find a
couple of volts there. Its this difference that is most likely screwing you
up. Your 5 volts may be 6 or 7, or possibly 3-4 when compared to the other
supply's ground.
If you absolutely must use two antagonistic power supplies, isolate them
from one another completely. Use a buffer chip for your serial lines. For
instance, I use a 74HC245 Octal bus transciever to act as a buffer between
the parallel port and an AVR processor. This protects the AVR from the
parallel ports higher voltages.
I'm not sure which chip would be appropriate for your application, I've only
researched things that I required - and I'm no expert!
Original Message
From: Sam [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=LIKQ2LiFxdKUi7faQMYqkIGFQ4DOi2Pza-H6kArGCQd47zSOyzBW8qpd6vYEtaO5mmBodFemjdwA-xCZ0OI]hard-on@t...[/url
Sent: August 6, 2003 8:21 PM
To: basicstamps@yahoogroups.com
Subject: [noparse][[/noparse]basicstamps] bizarre problem w/ ground
hey everyone,
I'm having a bizarre problem with common ground between my basic
stamp and another device. I have a tcm2-50 electronic compass hooked
up to a wall-wart and there are two serial lines (transmit and
receive) between this compass and my bs2sx. My bs2sx is powred by a
seperate wall-wart. For some reason, when I connect the grounds of
the two devices, my computer says "hardware not found" when I try to
download to the stamp. However, without the common ground wire, my
computer downloads to the bs2sx just fine. However, the serial
connection between the stamp and the periferal device does not seem
to be working correctly, so I think that I do need the common ground
wire...... does anyone know what is going on? Thank you very much for
any help.
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> You have to keep in mind that "ground" isn't actually ground. Its really AC
> common. If you look at the main circuit breaker panel for your house, you'll
> see three wires AND a ground going to it. Two are hot, one is common. Common
> is just the AC line that is mid-potential beween the two hots. Ground to the
> panel, not to earth.
Are you sure? If I'm not mistaken, I believe (at least in my
panel) that the commons (and the panel) are all tied together
with earth ground.
Cheers,
Michael
phase. Two "hot" wires (usually red or black, but can be any color
except white or green) and a neutral colored white. You get 120V between
any "hot" wire and the neutral and 240V between the two "hot" wires.
There is also an "equipment ground" which is green or bare wire. The
neutral and equipment ground are connected together at the "service
equipment", in a residence, this will usually be a panelboard with a
main breaker and a bunch of branch circuit breakers. The neutral and
equipment ground are ONLY to be connected together at the service
equipment. Yes, there is also a wire from this common neutral-equipment
ground connection that goes to a grounding electrode, usually a cold
water pipe, driven ground rods or a combination of the two.
Michael Burr wrote:
> PatM wrote:
>
>>You have to keep in mind that "ground" isn't actually ground. Its really AC
>>common. If you look at the main circuit breaker panel for your house, you'll
>>see three wires AND a ground going to it. Two are hot, one is common. Common
>>is just the AC line that is mid-potential beween the two hots. Ground to the
>>panel, not to earth.
>
>
> Are you sure? If I'm not mistaken, I believe (at least in my
> panel) that the commons (and the panel) are all tied together
> with earth ground.
>
> Cheers,
>
> Michael
>
>
> To UNSUBSCRIBE, just send mail to:
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>
>
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>
>
same as being earth ground. Neutrals carry current all the time while the
actual earth ground wires only carry current if something is broken. This
makes neutrals susceptible to the same ground loop problems as electronics.
Your "ground" can actually have voltage potential relative to earth and a
different potential at various points.
I'm not an electrician so I don't do a ton of electrical work. I've still
seen up to 10 volts between neutral and earth.
Original Message
From: Michael Burr [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=ChHTOkal1DHFeeYHeB-ASmQnFXipPrND5Fr0iY3f9HV8x2LHzCBaYDQXN0xXl6f2rPCWXvfft8LkEw]mburr@b...[/url
Sent: August 6, 2003 9:59 PM
To: basicstamps@yahoogroups.com
Subject: Re: [noparse][[/noparse]basicstamps] bizarre problem w/ ground
PatM wrote:
> You have to keep in mind that "ground" isn't actually ground. Its really
AC
> common. If you look at the main circuit breaker panel for your house,
you'll
> see three wires AND a ground going to it. Two are hot, one is common.
Common
> is just the AC line that is mid-potential beween the two hots. Ground to
the
> panel, not to earth.
Are you sure? If I'm not mistaken, I believe (at least in my
panel) that the commons (and the panel) are all tied together
with earth ground.
Cheers,
Michael
To UNSUBSCRIBE, just send mail to:
basicstamps-unsubscribe@yahoogroups.com
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ground as the sending device so, yes, you must have a common ground between
them.
jim
http://www.geocities.com/jimforkin2003/
Original Message
From: Sam [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=0jGqVlP9wh8gPHwd1ZWhCixUsvcmzfyYzZ-I6eQcMHALenL7MldYNmb6ayxQofFYM65pmX8m22BaKVAM]hard-on@t...[/url
Sent: Wednesday, August 06, 2003 11:21 PM
To: basicstamps@yahoogroups.com
Subject: [noparse][[/noparse]basicstamps] bizarre problem w/ ground
hey everyone,
I'm having a bizarre problem with common ground between my basic
stamp and another device. I have a tcm2-50 electronic compass hooked
up to a wall-wart and there are two serial lines (transmit and
receive) between this compass and my bs2sx. My bs2sx is powred by a
seperate wall-wart. For some reason, when I connect the grounds of
the two devices, my computer says "hardware not found" when I try to
download to the stamp. However, without the common ground wire, my
computer downloads to the bs2sx just fine. However, the serial
connection between the stamp and the periferal device does not seem
to be working correctly, so I think that I do need the common ground
wire...... does anyone know what is going on? Thank you very much for
any help.
To UNSUBSCRIBE, just send mail to:
basicstamps-unsubscribe@yahoogroups.com
from the same email address that you subscribed. Text in the Subject and
Body of the message will be ignored.
Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
one powering another device, and both devices connected by serial
wires and a common ground) before when using serial communication
between the stamp and other devices, and never had a problem... Also,
before I sent in the 'other device' (tcm2-50 electronic compass to be
checked for repairs) I put a voltmeter between the two grounds (when
they were'nt connected), and found no voltage. I just got word that
the tcm2-50 is functioning fine, so I have no idea what the problem
is or how to fix it. I emailed the tcm2-50 company for advice too,
I'll post it here if they have any, too.
--- In basicstamps@yahoogroups.com, PatM <pmeloy@s...> wrote:
> You have to keep in mind that "ground" isn't actually ground. Its
really AC
> common. If you look at the main circuit breaker panel for your
house, you'll
> see three wires AND a ground going to it. Two are hot, one is
common. Common
> is just the AC line that is mid-potential beween the two hots.
Ground to the
> panel, not to earth.
>
> The common wire is subject to the same sorts of ground loop
problems that
> you can experience in electronics. Although we call it ground, it
can have a
> positive or negative voltage potential relative to real ground. If
you put a
> volt meter between your two ground wires, dollars to donuts you'll
find a
> couple of volts there. Its this difference that is most likely
screwing you
> up. Your 5 volts may be 6 or 7, or possibly 3-4 when compared to
the other
> supply's ground.
>
> If you absolutely must use two antagonistic power supplies, isolate
them
> from one another completely. Use a buffer chip for your serial
lines. For
> instance, I use a 74HC245 Octal bus transciever to act as a buffer
between
> the parallel port and an AVR processor. This protects the AVR from
the
> parallel ports higher voltages.
>
> I'm not sure which chip would be appropriate for your application,
I've only
> researched things that I required - and I'm no expert!
>
>
>
Original Message
> From: Sam [noparse][[/noparse]mailto:hard-on@t...]
> Sent: August 6, 2003 8:21 PM
> To: basicstamps@yahoogroups.com
> Subject: [noparse][[/noparse]basicstamps] bizarre problem w/ ground
>
>
> hey everyone,
>
> I'm having a bizarre problem with common ground between my basic
> stamp and another device. I have a tcm2-50 electronic compass hooked
> up to a wall-wart and there are two serial lines (transmit and
> receive) between this compass and my bs2sx. My bs2sx is powred by a
> seperate wall-wart. For some reason, when I connect the grounds of
> the two devices, my computer says "hardware not found" when I try to
> download to the stamp. However, without the common ground wire, my
> computer downloads to the bs2sx just fine. However, the serial
> connection between the stamp and the periferal device does not seem
> to be working correctly, so I think that I do need the common ground
> wire...... does anyone know what is going on? Thank you very much
for
> any help.
>
>
> To UNSUBSCRIBE, just send mail to:
> basicstamps-unsubscribe@yahoogroups.com
> from the same email address that you subscribed. Text in the
Subject and
> Body of the message will be ignored.
>
>
> Your use of Yahoo! Groups is subject to
http://docs.yahoo.com/info/terms/