12v A2D circut with minimal power consumption

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What circuit and technique should I use for a lest power consuming design for 8 bit AVR measuring the charge of a 12V battery bank?

 

* Post your questions in the appropriate forum. The "AVR Freaks Projects" forum is for questions about existing, fully completed submissions in the "Projects" area. Moderator. *

Last Edited: Thu. Nov 22, 2018 - 01:07 AM
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One approach is to put a FET switch between the battery and the resistor voltage

divider that feeds the ADC input.  Switching it on to measure, then off, keeps current

consumption low. 

 

Here is a diagram for measuring a 9V battery:

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another example that's for a 4S Li-ion battery :

AVR1300: Using the AVR XMEGA ADC

(page 21)

via AN2535 AVR1300: Using the XMEGA ADC | Application Notes | Microchip Technology Inc. 

Adjust the source resistance as XMEGA can have a larger source resistance than megaAVR at a given sample rate.

 

Edit: source R

 

"Dare to be naïve." - Buckminster Fuller

Last Edited: Fri. Nov 23, 2018 - 07:16 PM
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I never posted a thank you for these circuits, Thank You! I have a related problem. I need a minimal power consumption AVR solution for 13.5-11V DC. Can I somehow beat the voltage divider method of powering this AVR? I want it to mostly sleep. 

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capnkeith wrote:
I need a minimal power consumption AVR solution for 13.5-11V DC.

Do you mean you need a voltage regulator for your project? 

One linear regulator I have used on past for a battery powered project was the TI LP2985, the quiescent current is only 95uA.

You may have even better results using a switching buck regulator, other freaks may be able to offer examples of these.

 

Good luck with the project.

 

Jim

 

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Thanks Jim! 95uA seems great. Can anyone do better? What about without a regulator just a voltage divider are there some combinations of resisters and uC that can beat this for total power consumption? Source is 12V marine battery bank...

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Go to Digikey and use their selector for  Product Index > Integrated Circuits (ICs) > PMIC - Voltage Regulators - Linear

 

Click on "More Filters" where you can select quiescent current along with maximum voltage input, voltage output and much more.

 

With selection of
Stock Status:          In Stock
Number of Regulators:  1
Max input Voltage:     18-60V
Quiescent current:     < 10 uA
Output Voltage:        5V
Dropout Voltage:       < 1V

 

I get 170 items.

 

Beware, if this is for an automotive application it will be quite nasty, start with the 60V max input.

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capnkeith wrote:
Source is 12V marine battery bank...

do you really need to worry about current drain with these, what is the amp/hour rating of your bank?

Jim

 

Click Link: Get Free Stock: Retire early! PM for strategy

share.robinhood.com/jamesc3274
get $5 free gold/silver https://www.onegold.com/join/713...

 

 

 

 

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There are a number of low drop out regulators of up to 0.2A or so with very low standing currents: the MCP1702 is 2uA.

 

Neil

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How big is this battery?  If you had a 50uA draw, in one month that is only 0.036 Ah total for the month, or 0.43 Wh.  Is that significant for a marine battery?  Doesn't seem likely (even the smallest marine battery seem to be rated for 100Ah).  The self-discharge rate should be looked at too...how much loss do you get with nothing at all connected?  If it self-discharges 5% per month on a 100Ah battery, that would be 5 Ah. 

When in the dark remember-the future looks brighter than ever.   I look forward to being able to predict the future!

Last Edited: Thu. Oct 24, 2019 - 07:41 AM