| Author |
Message |
jim
Guest
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 Posted:
Mon Nov 28, 2005 9:35 am Post subject:
Current measurement using 50mV shunt and AVR microcontroller |
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I want to build a little device that will measure current flow to/from my
deep cycle batteries. I want this use a microcontroller to provide data
collection etc. The currents involved will be 0-30amps, either direction (
load and charging).
I seems to me that the 50mV from the shunt is far too low a value to
measure directly with the AVR's ADC, not to mention the problem of the
"negative voltage" on the shunt with the battery is being recharged (and
yes, I do want to measure charge current as well.
The entire device will be powered by the battery system itself, using 7805
(or some similar 5V regulator) to supply Vcc for the AVR.
I'm guessing I'll need to use some sort of opamp circuit to scale the
-50mV-to-+50mV raw input to something like 0-2.56 volts to be read by the
ADC.
My question is... how do I do this.. I'm more of a digital type so I'm
looking for advice on this analog project.
thanks
- jim
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Iain Wilkie
Guest
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| Posted:
Mon Nov 28, 2005 5:35 pm Post subject:
Re: Current measurement using 50mV shunt and AVR microcontro |
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Consider the MAX472 chip
--
"jim" <jim22@trlp.com> wrote in message
news:pan.2005.11.28.06.47.17.324588@trlp.com...
| Quote: | I want to build a little device that will measure current flow to/from my
deep cycle batteries. I want this use a microcontroller to provide data
collection etc. The currents involved will be 0-30amps, either direction (
load and charging).
I seems to me that the 50mV from the shunt is far too low a value to
measure directly with the AVR's ADC, not to mention the problem of the
"negative voltage" on the shunt with the battery is being recharged (and
yes, I do want to measure charge current as well.
The entire device will be powered by the battery system itself, using 7805
(or some similar 5V regulator) to supply Vcc for the AVR.
I'm guessing I'll need to use some sort of opamp circuit to scale the
-50mV-to-+50mV raw input to something like 0-2.56 volts to be read by the
ADC.
My question is... how do I do this.. I'm more of a digital type so I'm
looking for advice on this analog project.
thanks
- jim
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jim
Guest
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| Posted:
Tue Nov 29, 2005 9:35 am Post subject:
Re: Current measurement using 50mV shunt and AVR microcontro |
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Thanks... Looks interesting.
On Mon, 28 Nov 2005 17:15:55 +0000, Iain
Wilkie wrote:
| Quote: | Consider the MAX472 chip
|
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Robert Baer
Guest
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| Posted:
Tue Nov 29, 2005 9:35 am Post subject:
Re: Current measurement using 50mV shunt and AVR microcontro |
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Iain Wilkie wrote:
| Quote: | Consider the MAX472 chip
More Maxim / Dallas vaporware? |
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Michael A. Terrell
Guest
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| Posted:
Wed Nov 30, 2005 1:36 am Post subject:
Re: Current measurement using 50mV shunt and AVR microcontro |
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Robert Baer wrote:
| Quote: |
Iain Wilkie wrote:
Consider the MAX472 chip
More Maxim / Dallas vaporware?
|
We all know you get a hardon every time someone mentions anything
made by Maxim. Get over it. You've cried about them for years and you
make yourself look like a fool.
--
?
Michael A. Terrell
Central Florida |
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Robert Baer
Guest
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| Posted:
Wed Nov 30, 2005 9:35 am Post subject:
Re: Current measurement using 50mV shunt and AVR microcontro |
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Michael A. Terrell wrote:
| Quote: | Robert Baer wrote:
Iain Wilkie wrote:
Consider the MAX472 chip
More Maxim / Dallas vaporware?
We all know you get a hardon every time someone mentions anything
made by Maxim. Get over it. You've cried about them for years and you
make yourself look like a fool.
Do tell. |
I have talked to a number of reps that quit handling Maxim due to the
sever problems of part availability.
Add that to the number of times i tried to get parts..even two for
eval - and there were zilch.
Perhaps you should make them sole source for all ICs... |
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Michael A. Terrell
Guest
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| Posted:
Fri Dec 02, 2005 9:35 am Post subject:
Re: Current measurement using 50mV shunt and AVR microcontro |
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Robert Baer wrote:
| Quote: |
Perhaps you should make them sole source for all ICs...
|
Maxim was about 20% of our IC usage and we never had any problems
with buying production quantities from them. I have never had any
problems getting any samples from them, or any data I needed. In fact,
the first time I contacted them directly they sent me a copy of every
databook they had in print after Pioneer failed to send me some
photocopies I requested, and didn't tell me about Maxim's samples
policy. In fact, Pioneer screwed me on the prices and took months to
get the parts. Maxim sent me the samples in three days. I no longer
deal with Pioneer in Orlando.
In case you don't know, they are either second sourced, or are second
source on a number of parts.
--
?
Michael A. Terrell
Central Florida |
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