Pages: [1]   Go Down
Author Topic: Solar powered mp3 playing Art project.  (Read 698 times)
0 Members and 1 Guest are viewing this topic.
Offline Offline
Newbie
*
Karma: 0
Posts: 6
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

Hello

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.
Logged

Austin, TX
Offline Offline
Faraday Member
**
Karma: 64
Posts: 6055
Baldengineer
View Profile
WWW
 Bigger Bigger  Smaller Smaller  Reset Reset

1. It needs to use as little power as possible because it’s solar powered (with some battery for winter and night time)
You're probably going to much less power from the solar panel than you think, so make sure you do some testing.

2. It needs an RTC that updates using GPS (every day or so)
What's the point of using a RTC if you're going to update it with a GPS?  Use the DS3231.  It's an incredibly accurate and stable RTC. 

I have not found a way for the mp3 player shield to use less power or be turned off yet (any ideas?).
Don't use mp3.  Look at the adafruit wave shield for an example of how to do audio (with wav files).  It'll use far less power than a mp3 decoder.

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.
I think you're overestimating the code or underestimating how much you can fit into the ROM.  I don't see any reason you couldn't use a single ATmega328.
Logged

Capacitor Expert By Day, Enginerd by night.  ||  Personal Blog: www.baldengineer.com  || Electronics Tutorials for Beginners:  www.addohms.com

Tasmania - Australia
Offline Offline
Sr. Member
****
Karma: 10
Posts: 299
View Profile
WWW
 Bigger Bigger  Smaller Smaller  Reset Reset

Hi, I did something similar some years back, here is what I did.

The project was a small art group wanting to create a very funky rubbish bin.
The rubbish bin is a 5 or 6 metre high sculpture with the rubbish bin integrated within.
When rubbish was placed into the bin, the bin would detect the rubbish going in and play a message via an audio amp and speaker within the bin.
The messaged played was a random selection from around 30 different wave files stored on an SD card on an Adafruit wave shield.
The messages were each in a different language and played a message of thanks for putting rubbish in the bin.
I recorded the messages using sound recording equipment I have, recording my old high school English teacher of many years back.
It was a total laugh, we had a fantastic time doing the recordings and the childrend love to go up to the rubbish bin and feed it with anything they can find.

I ended up being involved in the making of two of these sculptural rubbish bins, one fully solar powered and has its own internal battery that is re-charged by the solar panel.

The program sketch inside the Arduino is very very simple, it just detects a signal from a PIR sensor and then picks a random number which points to a wav file stored on the SD card.

Before I play the wav file I have the Arduino set one of its digital pins high that enables the audio amplifier to come out of shut-down mode.
Then after the wav file is finished playing I shut-down the audio amp again. This reduces the power consumption of the whole unit and allows it to work quite well from two small lead-acid batteries with the solar panel, which I recall is about 40 watts or thereabouts.

I made a selection of photos during the build, which I am sure I still have on my other computer if you are interested to see.

I hope this has been somewhat helpful for you.

Paul
Logged


Offline Offline
Newbie
*
Karma: 0
Posts: 6
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

Thanks to both of you for the fast feedback:)

James C4S,
I come from north norway so the sun is a challange at the best of times. So it will be large. I have used the DS3231 and agree that it works nicely. But i hope to have the project outside without service for 2-3 years and even the DS3231 will lose og gain some time at that scale. I was thinking about wave shield also, but i will have a very large selection of files. meny houres of content if possible. But i will get a shield and see what i can get out of it.

rockwallaby,
Thanks for the long feedback, yeah I would love to see some pictures and\or code for your funky rubbish bin. 
Logged

Seattle, WA USA
Online Online
Brattain Member
*****
Karma: 551
Posts: 46240
Seattle, WA USA
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

Quote
I was thinking about wave shield also, but i will have a very large selection of files. meny houres of content if possible. But i will get a shield and see what i can get out of it.
The wave shield plays music off of an SD card on the shield. You can store a lot of music on an SD card. The only drawback is that the music files must be in .wav format.
Logged

Tasmania - Australia
Offline Offline
Sr. Member
****
Karma: 10
Posts: 299
View Profile
WWW
 Bigger Bigger  Smaller Smaller  Reset Reset

I don't recall exactly, but with the wave shield I think if you don't want or need stereo you can simply have a mono file and possibly even set the sample rate lower of the audio wave file? It may be possible to store quite a bit more on any given SD card if this is the case, though this should be checked out against the specs of the wav shield itself.

I will look for any photos I have of the funky talking rubbish bin and post back tomorrow when I get a chance, if that is ok tronba.

Paul
Logged


Pages: [1]   Go Up
Jump to: