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Author Topic: To Regulate or not to Regulate?  (Read 363 times)
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I'm looking to run an Arduino off batteries for a few months unattended. I have read around the subject and various posts mention low drop-out regulators but I was wondering if I need a voltage regulator at all? If I am reading the Atmega 328 data sheet correctly it will run with the operating voltage in the 2.4 to 5.5V range if clocked at around 8MHz.

 4 x 1.2V NiMH rechargeables will give 4.8V which will drop off as they discharge, what is the advantage of a regulator in this situation?
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No regulator needed for that. Regulator is only needed to bring a higher voltage down into the 4.5-5.5V range.
If you're at  3.7-4.2 (LiPo), 4.5 (3 AAs, AAAs), 4.8 (4x NiCd), you're good to go as is.
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Unless you need exactly 5.0v to measure absolute voltage with A/D, instead of just relative.  There is another way to do it using Vref?
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Thanks for the replies. Looks like I'll skip the regulator.
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Quote
I'm looking to run an Arduino off batteries for a few months unattended. I have read around the subject and various posts mention low drop-out regulators but I was wondering if I need a voltage regulator at all?

You did not mention what else is connected to the Arduino or the application.  That can effect the answer.

Also "a few months unattended" caught my attention.  How will glitches be handled?  Are you familiar with watchdog timers?
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Car battery?
+
check - http://www.gammon.com.au/forum/?id=11497 - for investigations about power saving
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I'm looking at making a tipping bucket rain gauge that can be left in the field. The bucket tips will generate interrupts to wake the Arduino and log the time. There will be an RTC that can generate interrupts and can possibly act as a watch dog.

There will also be an SD card to log data that runs on 3.3V. This needs level shifting from 5V so that would need regulation but I'm thinking that the Arduino would turn this on after a certain number of interrupts, dump the data to it and then turn it off again.

I've got to hike up a hill with it so a Car Battery isn't top of my list. I can get 4AH NiMH D cells (or higher) so with an average draw of say 1mA that's plenty for 2 months (even with self discharge). Thanks for the links, I had seen that.
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Have you thought about maybe including a solar charger to top off the batteries?  Something like this perhaps? https://www.sparkfun.com/products/11496

Obviously for rain/night you would need the heavier car battery, but I assume it would extend the usage before you need to truck up another car battery.
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Yes I had thought about solar but I'm not sure the complexity is worth it. I think something like that would be hard to weather proof and this is at 54deg north so even if there is any sun the power is reduced.

Also it's easier and cheaper just to add more the batteries in parallel if more power is needed
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