I’m planning an arduino project, the project will measure a distance with an hc-sr04 ultrasonic sensor. every 7 seconds it will take a measure and it will send data over internet, via wifi every 30 minutes, the position of the sensor makes it very difficult and expensive to replace the batteries so i need to use the best battery solution possible to make it work for at least 6 months without replacing the batteries.
Which arduino model should i use to get the best battery life?
Which wifi module should i use to get the best battery life?
Which battery should i use to have the best autonomy possible?
Starting point is to get some kind of a power budget before you need to worry about ‘how big the battery is’.
Unless the peripherals can be put into a really low power mode, you may have to have switched power for the hc-sr04 and the WiFi module. To save power, the peripherals should only be enabled for the minimum amount of time, so the question is then ‘how quickly are the peripherals available after switching them on’.
Also bear in mind that having a decent antenna on your Wifi connection (both ends) can considerably cut down DC input power requirements.
If you want a low power CPU do some research and learn about the low power modes of the various part available that are packaged for Arduino.
You will probably also need to learn about the evils of back-powering (ex: driving current from an active CPU into an powered peripheral).
The whole art of low-power electronics is quite fascinating, and done right, this project has the possibility of allowing to learn a great deal.
-Mark
That should read “You will probably also need to learn about the evils of back-powering (ex: driving current from a powered/active CPU into an unpowered peripheral”.
-Mark
And vice versa. Found out the hard way that voltage on a PIC pin would flow through the protection diode and power up the chip. I’m fairly sure that an AVR would do the same.
FWIW, I agree 100% with what Mark said. Figure out how much power you need * duty cycle * battery life hours wanted and then pick your battery. Sleeping and keeping peripherals off when not being used is key. You may want to skip using a dev board and go straight to a bare chip to eliminate the constant drain of the regulator and any USB interface it may have. You can possibly run the chip slow using a 32khz xtal and really lower the power consumption of the processor. Obviously your code will run slower, but it may not matter in your application.
Can you add a solar cell?
Edit:. My formula is simplistic, you need to factor in your power used when sleeping. I think you get the idea though.
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