Sketching out a project that will employ 5-10 sensors to Arduino Diecimilia, likely using Fluxamasyynth http://shop.moderndevice.com/products/fluxamasynth to run some battery powered speakers. Size/weight of the power source isn't an issue, but it will need to run for several hours. Sensors will likely be flex, IR rangers, photocells. For whatever reason the 4 x AA pack just doesn't seem to me like it will have the endurance. Any advice would be appreciated!
Any advice would be appreciated!
Advice is to first measure the total current being consumed with all the sensors attached and working. Only then do you have the measurement fact needed to determine the millamp hour rating to select the battery capacity size you require. Battery capacity is rated in mah, so it's just a simple math exersice to determine what size battery is need for your two hour run time specification.
Lefty
retrolefty:
Any advice would be appreciated!
Battery capacity is rated in mah, so it's just a simple math exersice to determine what size battery is need for your two hour run time specification.
That will get you a "rough estimate" - you really need to look at the battery's spec sheet to get the full answer, because their amp-hour rating is based on a specific level of current draw. The amp-hour rating changes (de-rating) depending on if the current draw goes over this amount, what the temperature (and other environmental factors) are, etc. All of that information is given in the spec sheet for the battery.
So a battery rated for 7 aH of capacity likely won't give you 7 hours of run-time if you are only drawing an amp from it; that value of 7 aH might be for a current draw of around 750 mA or less, for example - but you won't know it until you look at the spec sheet...
retrolefty:
Battery capacity is rated in mah, so it's just a simple math exersice to determine what size battery is need for your two hour run time specification.
Ok thanks, honestly I'm fairly novice the calculation side of circuits...last time I tried to measure low-voltage current via multimeter it seemed like the math didn't work out. Would I have to measure it ahead of the Arduino's built-in voltage regulator?
Would I have to measure it ahead of the Arduino's built-in voltage regulator?
Yes, you want to measure the current being used at the battery terminals, so that regulator overhead current is also included as the battery doesn't care how or what is consuming the current, just how much is being consumed.
Lefty
Probably worth multplying the theoretical capacity by 2 to allow for battery capacity reducing with age and to prevent over-discharge of the battery (this is usually pretty bad for rechargeable batteries).