Hi,
I'm making an environment logger (temperature and humidity) that I hope to use to log data every 5 minutes to an SD card. Once every few hours it will also send an SMS with a summary of the previous hours data.
I've worked with SD cards, temperature modules and SMS modules before so I'm pretty happy with that aspect of the work. The problem is that I was hoping to leave the module unattended for a 3-4 weeks connected to a 12v lead-acid battery, but to do this I'm going to have to implement some stringent power-saving methods.
I've read Nick Gammons excellent article here Gammon Forum : Electronics : Microprocessors : Power saving techniques for microprocessors
My first question is has anyone done any work on hacking a mega to convert it to a bare-bones board - i.e. removing the power-hungry components. I don't want to have to try building a cut-down arduino myself.
Secondly, I think I'm going to need to somehow switch on (and off) a regulator to power my SMS module (and maybe my SD card too). Has anyone got a circuit example of doing this (hopefully including part numbers, not just 'use a MOSFET')
Finally, any other suggestions?
thanks
i.e. removing the power-hungry components.
What components are these?
Why don't you use some solar cells to top up the batteries? Lead acid batteries are pretty immune to overcharge, so if you arrange to put about 14.2 v. into then during most of the daylight period, you might keep them charged forever. What you do is use a zener diode at the input from the solar cells so that only a voltage greater than, say 12 v. gets to the batteries. (You might want to do this through a boost regulator which can take any voltage above, say 5 v., and provide a 14.2 v. input.) At night, the zener prevents the battery draining through the solar cells. It's admittedly a crude charger system, but I used this scheme to operate yard lights indefinitely with only the solar charge applied.
Of course, you have to either buy a suitable solar cell array, or gin one up from single cells.
i.e. removing the power-hungry components.
What components are these?
to quote from Nick Gammon's article....
huge overhead of the voltage regulator and USB interface chip.
Basically, Nick suggests building up a bare-bones board from scratch, I was wondering if it would be easier to start with a off-the-shelf development board and strip it down.
Why don't you use some solar cells to top up the batteries?
The environment I'm monitoring is inside a vehicle parked inside a barn. - it doesn't get much sunlight.
To be honest, the easiest solution is probably to use a bigger battery and visit it more often to check it's charged ok, but I'd prefer a more elegant solution if possible