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Switzerland
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Hy

At the moment I'm running an Arduino with an 1S LiPo (3.7V) with an
5v Step-Up regulator. Now I like to monitor also the lipo voltage with
an Analoge input. But when I do connected the battery to an Analog
Input it always reads ~5V.

How can I get the real value of around 4V?

I know this question has alredy been asked in the old forum but the solution didn't worked...

Thx
Andy
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Left Coast, CA (USA)
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That doesn't sound right at all. Could you post a drawing showing how you have wired the batter/dc-dc convertor/arduino power and analog input pin/ and all the gound connections ?

 I'm pretty sure you must have something wired incorrectly. What you wish to do should be straight forward.

Lefty
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Switzerland
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Hope this helps...
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Manchester (England England)
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It is possible that the step up regulator is generating noise that is giving you a false reading. Try and have a potential divider across the battery and measure across the bottom resistor. Also put some capacitance across the input, to try and reduce the noise.
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Switzerland
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R1=56k
R2=15k

Battery is 4.1V
Arduino gives me back: 1.94V this would mean =7.24V?????

(If I calculated right the Arduino should read 0.866V or am I wrong?)
« Last Edit: March 07, 2011, 04:26:20 pm by GekoCH » Logged

Manchester (England England)
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Put a capacitor across R2 to remove noise.
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Do you have a link to that DC/DC converter? I'm wondering if it could be an isolated converter (no ground continuity from input to outout) ?  If not, can you use a ohm better and see if the negitive in and out pins show continuity?

 The first way you showed it wired up should work if it's not a isolated converter. Not sure about it being a noise issue or not, only a scope would verify that or not.


Lefty
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Quote
can you use a ohm better

Theirs no place like ohm.
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Quote
can you use a ohm better

Theirs no place like ohm.

My spell checker is as dumb as dirt.  smiley-grin
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Switzerland
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Do you have a link to that DC/DC converter? I'm wondering if it could be an isolated converter (no ground continuity from input to outout) ?  If not, can you use a ohm better and see if the negitive in and out pins show continuity?

 The first way you showed it wired up should work if it's not a isolated converter. Not sure about it being a noise issue or not, only a scope would verify that or not.


Lefty


The converter is this one.
http://www.bodhilabs.com/vpackbareaaa.html

Do you know a better one?
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Manchester (England England)
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What lefty means is try and connect the battery -ve directly to the arduino -ve, not "through" the board.

Sorry the link is not much help, we need to see a schematic.
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Is this a standard Arduino (Uno, Duemilanove) or something you built?

Two measurements that would eliminate a lot of speculation are as follows:

- Voltage between Arduino Aref and Arduino Gnd
- Voltage between Battery + and Arduino Gnd

If you post these measurements, I'm sure you'll get some useful answers.
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