Remote measurement of current? Possible?
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Posts: 46,084
Hello group,
Thanks for the great advice on my long distance communication
problem, I'd like to pick your brains on something else now [noparse]:)[/noparse].
Would it be possible for a robot to measure the current it was
consuming from its battery, digitize that information, and send it
back to the operator? The current consumption would vary between
about .5 and 12 amps depending on the mode in which the robot was
operating. If it is possible, is it possible to build such a system
in the $10-$20 price range? (microcontroller already exists, as does
serial communication link with operator, and I think a spare 8 bit
ADC or two is floating around on the serial bus if that would be of
any help.)
Thanks in advance for the always great response,
Doug McClean
Thanks for the great advice on my long distance communication
problem, I'd like to pick your brains on something else now [noparse]:)[/noparse].
Would it be possible for a robot to measure the current it was
consuming from its battery, digitize that information, and send it
back to the operator? The current consumption would vary between
about .5 and 12 amps depending on the mode in which the robot was
operating. If it is possible, is it possible to build such a system
in the $10-$20 price range? (microcontroller already exists, as does
serial communication link with operator, and I think a spare 8 bit
ADC or two is floating around on the serial bus if that would be of
any help.)
Thanks in advance for the always great response,
Doug McClean
Comments
the battery and measure the voltage across it with a differential ADC
channel (most multi channel ADCs can measure differential or at least
pretend to do so).
They make resistors especially for this purpose with values of .1 and .01
ohms. So if you have a 12V system drawing, say, 5A nominal, a .1 resistor
will read .5V at 5A. Of course, this will drop .5V from the system (11.5V).
A .01 will only read 50mV, but make the drop that much less (11.95V). Power
is a factor (I**2 x R) 5A**2 * .1 = 2.5W.
There are other magnetic ways to do it where you don't lose power
monitoring, but that is usually too complex. Get any Maxim 2 channel A/D
(did you guys hear Maxim bought Dallas?) and a $.50 resistor (get 'em at
DigiKey) and away you go.
Regards,
Al Williams
AWC
* Expand your Stamp I/O! On sale now:
http://www.al-williams.com/awce/pak3.htm
>
Original Message
> From: IDiggles@a... [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=8V9aytfbkUvJJoqcBcUVfzX49k67bdpA7uuUcOBsZQeNGXO6Q6iSIyJqiVTADmiNXp0AzGJIag]IDiggles@a...[/url
> Sent: Saturday, February 03, 2001 10:18 AM
> To: basicstamps@yahoogroups.com
> Subject: [noparse][[/noparse]basicstamps] Remote measurement of current? Possible?
>
>
> Hello group,
> Thanks for the great advice on my long distance communication
> problem, I'd like to pick your brains on something else now [noparse]:)[/noparse].
>
> Would it be possible for a robot to measure the current it was
> consuming from its battery, digitize that information, and send it
> back to the operator? The current consumption would vary between
> about .5 and 12 amps depending on the mode in which the robot was
> operating. If it is possible, is it possible to build such a system
> in the $10-$20 price range? (microcontroller already exists, as does
> serial communication link with operator, and I think a spare 8 bit
> ADC or two is floating around on the serial bus if that would be of
> any help.)
>
> Thanks in advance for the always great response,
> Doug McClean
>
>
>
of myself. [noparse]:)[/noparse] Sounds like it'll work beautifully (and be dirt cheap).
It might also be possible if the power turned out to be a big factor,
to use the smallest resistor i can find and then amplify the voltage
drop if neccessary to get better resolution (not that resolution is
all that critical for my application).
Unexpressably gratefully,
Doug McClean
--- In basicstamps@y..., "Al Williams" <alw@a...> wrote:
> The easy way to monitor current is to place a small resistor in
series with
> the battery and measure the voltage across it with a differential
ADC
> channel (most multi channel ADCs can measure differential or at
least
> pretend to do so).
>
> They make resistors especially for this purpose with values of .1
and .01
> ohms. So if you have a 12V system drawing, say, 5A nominal, a .1
resistor
> will read .5V at 5A. Of course, this will drop .5V from the system
(11.5V).
> A .01 will only read 50mV, but make the drop that much less
(11.95V). Power
> is a factor (I**2 x R) 5A**2 * .1 = 2.5W.
>
> There are other magnetic ways to do it where you don't lose power
> monitoring, but that is usually too complex. Get any Maxim 2
channel A/D
> (did you guys hear Maxim bought Dallas?) and a $.50 resistor
(get 'em at
> DigiKey) and away you go.
>
> Regards,
>
> Al Williams
> AWC
> * Expand your Stamp I/O! On sale now:
> http://www.al-williams.com/awce/pak3.htm
>
>
> >
Original Message
> > From: IDiggles@a... [noparse][[/noparse]mailto:IDiggles@a...]
> > Sent: Saturday, February 03, 2001 10:18 AM
> > To: basicstamps@y...
> > Subject: [noparse][[/noparse]basicstamps] Remote measurement of current? Possible?
> >
> >
> > Hello group,
> > Thanks for the great advice on my long distance communication
> > problem, I'd like to pick your brains on something else now [noparse]:)[/noparse].
> >
> > Would it be possible for a robot to measure the current it was
> > consuming from its battery, digitize that information, and send it
> > back to the operator? The current consumption would vary between
> > about .5 and 12 amps depending on the mode in which the robot was
> > operating. If it is possible, is it possible to build such a
system
> > in the $10-$20 price range? (microcontroller already exists, as
does
> > serial communication link with operator, and I think a spare 8 bit
> > ADC or two is floating around on the serial bus if that would be
of
> > any help.)
> >
> > Thanks in advance for the always great response,
> > Doug McClean
> >
> >
> >
gives 1 millavolt per 1 amp www.jameco.com part # 162309 $24.95 on page
128 of new cat. and it has with stood 4 years cont service on my solar setup
thnx. carl
Original Message
From: "Al Williams" <alw@a...>
To: <basicstamps@yahoogroups.com>
Sent: Saturday, February 03, 2001 10:00 AM
Subject: RE: [noparse][[/noparse]basicstamps] Remote measurement of current? Possible?
> The easy way to monitor current is to place a small resistor in series
with
> the battery and measure the voltage across it with a differential ADC
> channel (most multi channel ADCs can measure differential or at least
> pretend to do so).
>
> They make resistors especially for this purpose with values of .1 and .01
> ohms. So if you have a 12V system drawing, say, 5A nominal, a .1 resistor
> will read .5V at 5A. Of course, this will drop .5V from the system
(11.5V).
> A .01 will only read 50mV, but make the drop that much less (11.95V).
Power
> is a factor (I**2 x R) 5A**2 * .1 = 2.5W.
>
> There are other magnetic ways to do it where you don't lose power
> monitoring, but that is usually too complex. Get any Maxim 2 channel A/D
> (did you guys hear Maxim bought Dallas?) and a $.50 resistor (get 'em at
> DigiKey) and away you go.
>
> Regards,
>
> Al Williams
> AWC
> * Expand your Stamp I/O! On sale now:
> http://www.al-williams.com/awce/pak3.htm
>
>
> >
Original Message
> > From: IDiggles@a... [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=_Gqd_2B13ANARW1aRdapW6KL8a8SvhbOQutXbAc57A0vgqnGBEjSxWnr0hTMuvoSqf-QI_m4pnC_Vw]IDiggles@a...[/url
> > Sent: Saturday, February 03, 2001 10:18 AM
> > To: basicstamps@yahoogroups.com
> > Subject: [noparse][[/noparse]basicstamps] Remote measurement of current? Possible?
> >
> >
> > Hello group,
> > Thanks for the great advice on my long distance communication
> > problem, I'd like to pick your brains on something else now [noparse]:)[/noparse].
> >
> > Would it be possible for a robot to measure the current it was
> > consuming from its battery, digitize that information, and send it
> > back to the operator? The current consumption would vary between
> > about .5 and 12 amps depending on the mode in which the robot was
> > operating. If it is possible, is it possible to build such a system
> > in the $10-$20 price range? (microcontroller already exists, as does
> > serial communication link with operator, and I think a spare 8 bit
> > ADC or two is floating around on the serial bus if that would be of
> > any help.)
> >
> > Thanks in advance for the always great response,
> > Doug McClean
> >
> >
> >
>
>
>
>
puts out a rectangular wave with duty cycle proportional
to the current [noparse][[/noparse]-7 to +7 amps] - this could modulate
a transmitted tone or otherwise be used as you wish.
You could use an external shunt resistor to increase
the current capacity of the chip....
[noparse][[/noparse]http://www.national.com for data sheet].
>>>
Date: Sat, 03 Feb 2001 16:17:36 -0000
From: IDiggles@a...
Thanks for the great advice on my long distance communication
problem, I'd like to pick your brains on something else now [noparse]:)[/noparse].
Would it be possible for a robot to measure the current it was
consuming from its battery, digitize that information, and send it
back to the operator? The current consumption would vary between
about .5 and 12 amps depending on the mode in which the robot was
operating.
SNIP
<<<
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