Hi! I have an Arduino Pro Micro (ATmega32U4 5V 16MHz). See: https://www.sparkfun.com/products/12640
Normally I power it with the USB cable but now I would like to power it with a battery because I wish to design a portable device.
Which voltage do I need? (5V?)
Should I buy a battery of litium? Or any other concrete type in order to have large duration? (Let's say 240 hours).
Due to space limitations I would like it to be very small (that is very important!), like a coin cell, and also flat, if possible.
Can someone send me an Ebay link where I can buy it cheap?
5v - but I think you can configure the chip to run at 8mhz, at which point you can run it at 3.3, which gets it into single cell range.
Since you care about power use, power it directly, not through regulator.
For coin cells, anything not lithium is useless. These are primary batteries, not rechargable. The battery life is often poor.
You can get LiPo batteries in approximately rectangular form factors, some quite small.
No matter what, you'll have to be very careful with power usage - you'll need to remove or disable the power led and probably the voltage regulator to get power usage down - the power light alone would require ~2 smart-phone-battery size batteries to last 240 hrs. Have you read nick gammon's power management articles? They're required reading.
In order to size the battery, you'll need to first get your sketch running and measure the power use - then you can multiply that by 240, and get the number of mAh that you need in theory. Then double that because manufacturers of batteries all exaggerate their specs.
DrAzzy:
5v - but I think you can configure the chip to run at 8mhz, at which point you can run it at 3.3, which gets it into single cell range.
Since you care about power use, power it directly, not through regulator.
For coin cells, anything not lithium is useless. These are primary batteries, not rechargable. The battery life is often poor.
You can get LiPo batteries in approximately rectangular form factors, some quite small.
No matter what, you'll have to be very careful with power usage - you'll need to remove or disable the power led and probably the voltage regulator to get power usage down - the power light alone would require ~2 smart-phone-battery size batteries to last 240 hrs. Have you read nick gammon's power management articles? They're required reading.
In order to size the battery, you'll need to first get your sketch running and measure the power use - then you can multiply that by 240, and get the number of mAh that you need in theory. Then double that because manufacturers of batteries all exaggerate their specs.
Hi! First of all, thanks a lot Your response was very very good.
The think is that I haven't buy the arduino Pro Mini yet. Do you think is better if I buy the 3.3V and 8mHz version? (I don't understank which is the implication of this 8mHz instead of the 16mHz that the 5V version provides)
I have been looking at the batteries you told me. The think is that LiPo batteries are 3.7V and coin cells 3V (so in any case in would need too right?). If I use a LiPo battery or 2 coin cells in a battery holder... do I need to power my arduino from RAW or VCC? Because you tell me not to use the regulator... but I don't understand what you mean.
Can I compute the size of the battery at the end? Now I'm just trying to build the prototype but since it is not finished (I'm doing it by parts) I haven't calculated the mAh requiered.
If you run on batteries, you have to make sure that you don't go over 5.5V.
UNO and most Arduinos have a 7805 regulator that needs 7V just to cut down to 5V, all excess is wasted into heat.
Look for DC-DC converters. They waste only a small amount, the rest is converted to more current available at the output voltage. And be aware of the ratings, my cheap ones are good to 3A of output whic is okay since the board is only okay up to 0.2A... but I can run small motors, more leds, etc with my 3A.
Converters can be boost, where voltage is boosted and current less or buck that lower voltage or some can do either and the cost is like both!
At 8 MHz and AVR can run at around 3V and save power. If you build your own, you don't need a clock crystal or the 2 capacitors and you get use of the 2 pins used by external clock.
With power saving code and not reading too often, AVR dataloggers have been known to fit in matchboxes and run weeks to months on a battery.
I have an Arduino Pro Micro (ATmega32U4 5V 16MHz). See: https://www.sparkfun.com/products/12640
Your response was very very good.