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Topic: Some advice on power efficeincieny (Read 588 times) previous topic - next topic

ppumkin

Hi
I usually make Arduino protos without worrying about power- there will always be power so why worry. Recently I was asked to make simple device that counts clicks/ticks and logs its somewhere. Easy enough-but the problem is it needs to run concealed inside a device for 3-5 years of a battery.
I came  across this
http://interface.khm.de/index.php/lab/experiments/sleep_watchdog_battery/
and the theory is that it can run up to 3 years. Its fantastic because it is nearly what I want.
Has anybody every actually run a device like this for 3-5 years of a battery? In research i came to the conclusion that using Lithium Polymer would be the best battery for long term power- am I correct? and using a single 700mAh LiPo could technically last to 5 years. Is this lifetime of a battery even feasible?

Now I will try and change that project to wake the Arduino every time i get an external tick/click and it will increment.

The second part is- Is it possible to store simple small integers inside the Arduino non-volatile memoery somehow to avoid keeping it in RAM and using power?

I appreciate any suggestions.

fm

#1
Oct 22, 2011, 07:37 pm Last Edit: Oct 22, 2011, 07:41 pm by fm Reason: 1
With the atmega328P you can have a very low power consumption on you application. The slower the clock speed the more power you will be able to save. It also depends on how much time your application needs to be active.
From what I can understand, you are going to be waking up on external line interrupt. How often and how much processing time will determine how long you are going to endure.
Battery wise it is difficult to tell, my record is 3 years +- a few months with alkaline batteries.
If you are interested on a similar assembly, but in SMD, to the one in the link you've posted look for the arduCHIP in this forum. It is a board I have designed for similar purposes.
Lipo batteries are perhaps your best call as they have the best shell life span than other technologies without being too expensive.
Careful with placing them on very hot places (over 45C) as they might catch fire.
   

engblaze


In research i came to the conclusion that using Lithium Polymer would be the best battery for long term power- am I correct? and using a single 700mAh LiPo could technically last to 5 years. Is this lifetime of a battery even feasible?


We haven't had any projects run for years yet, but it's feasible, and I know of others that have.  If you use rechargeables, you may lose some of your battery energy just due to normal discharge over time, regardless of whether the Arduino is drawing power.  LiPo/Li-ion is the best option in terms of energy density, but if you don't care about size/weight, other options might do the trick for less money. 700mAh isn't huge, so you have options.

Keep in mind that if you're using a standard Arduino board there will be other components on it that are always drawing power, such as the voltage regulator and FTDI chip.  To get maximum power savings, you'll have to use a custom board.

We've been working on compiling info on sleep modes on our site and just posted our first article on the topic, you can check it out for more info: http://www.engblaze.com/2011/10/hush-little-microprocessor-avr-and-arduino-sleep-mode-basics/


The second part is- Is it possible to store simple small integers inside the Arduino non-volatile memoery somehow to avoid keeping it in RAM and using power?


Yes, with a bit of additional work.  You can use PROGMEM or EEPROM to store data long-term, they're both non-volatile: http://www.arduino.cc/playground/Code/EEPROM-Flash.  However, if your chip is sleeping but still on in order to record ticks from time to time, you can still use RAM.

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