Hi all, I am sorry in advance if this has already been answered, if so please point me in right direction.
Im not new to coding in general and have some basic knowledge of electronics, but particularly Arduino and C are new things to me so I need your help understanding something:
If I have a program that queue few buttons and when button is pushed it lights up an LCD screen and start doing other things, but most of the time arduino has everything off and only listens for button presses. How much of battery life can I expect?
I'm looking for proper way to keep device in sleep mode until button is pressed, so far only solution I can think of it to keep constantly looping function that listens for button pressed, but that apparently will drain some battery juice.
There are a number of ways to reduce current consumption. Using an interrupt to wake up the Arduino will allow the Arduino to sleep most of the time, and still not miss switch presses.
How much of battery life can I expect?
From a 9V battery? Not much. From 3 or 4 AA batteries? A lot longer.
Keep in mind that the main loop of the arduino code is running all the time even if it's just waiting for something to happen. Unfortunately the sleep functions of the arduino don't save much power.
As Paul suggested an interrupt would help reduce that further but the voltage regulator is not very clean and it's burning quite a bit just letting the power through. And it's on all the time, interrupt or not.
Here's a good suggestion for a off board solution.
The other option is to choose a different board. There are some very low power arduino or arduino clone boards made for the mobile or wearable market.
Keep in mind too, for the standards like the Uno, it can handle a main voltage of 12 volts (and perhaps even higher but don't quote me) so that may allow more capacity based on your battery considerations. (what I don't know is how the regulator handles more juice and is it burning even more at a higher source level, thereby reducing any gains.)
Thanks for reply, yeah when I say Arduino I do not mean Arduino Uno, I use it for prototype. For final version I am planning to rebuild project on arduino pro mini 3.3v, and use interrupts to conserve as much power as possible.
Unfortunately sleep mode did not work well for what I need because I use timer and keyboard interrupts and somehow they get messeed up when device comes back from sleep mode.
I think instead of 9v battery I will try to use 2 AA batteries with step up voltage regulator to boost it to 3.3v, or maybe 4 AA batteries with step down regulator is that a good idea?
A 3.3v Arduino will probably run perfectly well off 2 x AA alkaline batteries.
My Mega works fine from 3 x AA cells connected to the 5v pin. I have an Atmega 328 on a breadboard running off 2 x AA cells - it runs at 8MHz using its internal oscillator.