Hi, I am working on a low-power arduino-based project, and I'd like to use a lipo battery for the job. As it is a low-power situation, I'd like to bypass the on-board voltage regulator on the arduino. Also, I'm considering using one of the 3.3V-8 MHz arduino pro minis.
But a lipo starts at 4.2 V. My question is: is that too much voltage for a 3.3V arduino? Am I better off using a 5V arduino?
I'm a little confused about all this, because on the one hand, I see stuff about the ATMega328 working down to 1.8V...If there's such a range, why do people refer to a 5V arduino and a 3.3V arduino?
snapster:
Hi, I am working on a low-power arduino-based project, and I'd like to use a lipo battery for the job. As it is a low-power situation, I'd like to bypass the on-board voltage regulator on the arduino. Also, I'm considering using one of the 3.3V-8 MHz arduino pro minis.
But a lipo starts at 4.2 V. My question is: is that too much voltage for a 3.3V arduino? Am I better off using a 5V arduino?
I'm a little confused about all this, because on the one hand, I see stuff about the ATMega328 working down to 1.8V...If there's such a range, why do people refer to a 5V arduino and a 3.3V arduino?
Less confusing when you know that the ATMEGA has an operating range of from 1.8V to 5V. You get to choose what voltage you run it at. As the voltage is lowered, the maximum specified operating frequency falls too.
So at 5V they are normally run at 16Mhz and at 3.3V its 8Mhz.
People prefer to use 5.0 and 3.3V because many sensors and other peripheral devices require one of those voltages.
If you choose sensors with a wider operating voltage range, you can run the ATMega chip at any appropriate voltage between 1.8 and 5.0 V.
snapster:
Hi, I am working on a low-power arduino-based project, and I'd like to use a lipo battery for the job.
So obvious question, why ?
-I already have a lipo + solar charge unit
-high power density battery, good for many charge cycles
-this project is not low-power all the time, but for long periods of time I'd like it to conserve energy as much as possible.
Why not use 6 nimh cells and put your micro to sleep when not needed?
I'm not following...what would the advantage of using nimh be over using a lipo? I certainly will be putting the arduino to sleep when not in use though.
snapster:
I'm not following...what would the advantage of using nimh be over using a lipo? I certainly will be putting the arduino to sleep when not in use though.
The 'project' as you have described it so far seems ideal for supply from AA Alkalines or indeed NiMh. They could be made to last years.
But since you have provided no information on what this project actually does, everyone is just spending time guessing.
So the project will use a couple of ping sensors somewhat continuously for, say, 1 hour per day, and the whole thing will go into low-power mode for the remaining time. During that 1 hour, it will be using probably 60-100 mA current, and in the remaining time, it ought to use very little current. So alkalines will be insufficient, as they won't be able to satisfy the high-load times for long.
My current plan is to use a lipo that is solar-recharged.
But again, what I'm confused about with your note is why nimh would be preferable to lipo? Does it have something to do with the voltage that makes it work better with the arduino?
So alkalines will be insufficient, as they won't be able to satisfy the high-load times for long.
Nonsense. The energy density by volume of alkaline batteries is higher than any other commonly available battery. See http://www.allaboutbatteries.com/Battery-Energy.html
Something to note is that lipos for long term use should be kept about 40% charged.
Float charging and keeping them at full charge is not a good idea, they really need to be cycled or float charged to 40% capacity.
snapster:
So the project will use a couple of ping sensors somewhat continuously for, say, 1 hour per day, and the whole thing will go into low-power mode for the remaining time. During that 1 hour, it will be using probably 60-100 mA current, and in the remaining time, it ought to use very little current. So alkalines will be insufficient, as they won't be able to satisfy the high-load times for long.
Now we have that information, it sounds like an ideal application for a small gel lead acid battery.