I am planning an solar powered arduino art project and would really like some feedback on how this is best done.
What I want to make is an mp3 player that plays mp3s every 2 hour. Dependent on the time and day different mp3s are played. For instance every Friday at 2200 it will play a random file from a special playlist. It will have a small amplifier and watertight speaker.
As I see it there is 3 main challenges to making this work.
1. It needs to use as little power as possible because it’s solar powered (with some battery for winter and night time)
2. It needs an RTC that updates using GPS (every day or so)
3. It needs to be encapsulated to handle weather.
If I start with what I have been thinking about power. I plan on using an Arduino nano (ATmega328) And this SD \ MP3 shield (http://gravitech.us/mp3pladforar.html
). The nano will not power the FTDI chip if not run on USB power, this will save some power. GPS will be used, but by connecting it’s power pin to an relay and only turning it on right before an RTC time update is done a lot of power is saved. Same goes with the small amplifier and speaker. The MP3s will be in different length from a few seconds up to 90 minutes per track. Making the nano sleep while it’s not playing anything will also help on power consumption. (perhaps using an Timer Overflow for the interrupt?). I am also thinking about using Prescale to save power when mp3 player is running (mp3 player only needs about 1/3 of processing power from the arduino).
I have not found a way for the mp3 player shield to use less power or be turned off yet (any ideas?).
This is a large project and the needed features might eat up to much of the ROM. One idea here is to use 2 arduinos. The first keep time, and trigger a relay to start the second. The 2nd arduino gets time from the first using serial transfer, find the right track on SD and play this. After the track is played the 2nd arduino sends message to the first. The first then shuts down the 2nd and goes itself to sleep. This would fix the power usage of the mp3 shield and might be the best way to do it.
This project is still in very early stage, I have done some smaller projects but I don’t know if my approach here is the best or if there might be a much simpler way. So if anyone have an idea about how I could approach the problem that would be nice.