project help - outdoor audio security message

Hi all, I need your help with an idea for a project that has the following specs:

A timed on-off control. (On at 10:30 pm and off at 7:30 am) Solar powered with a rechargeable battery (recharged by the sun) Voice message “[The SPA is now closed. Please leave the area.]” Motion sensor to trigger voice message

My thoughts on hardware: -Wave Shield to handle the audio -PING or PIR sensor (or both) to handle the motion sensing

Questions: Solar power? I have no idea where to start (this unit will have sun access) Timed control? How do I program the code to keep track of time? Weather proof case?

Any thoughts or ideas would be appreciated...

depending on the exact recording you may be able to get away without a wave shield (8 bit mono sound loaded into progmem and a simple resistor dac)

Solar power, depends on battery I think (i have not messed around with it personally)

Timed control can be done with a RTC (realtime clock module)

Weatherproof boxes, while not cheap do exist, for example http://www.pactecenclosures.com/Plastic-Enclosures/OD-Series.html

I think the only trouble spot will be going solar. Its all a matter of getting the right battery and being sure that you have enough solar cells to keep it charged. There is always the chance the project will drain the battery faster then it can charge. Especially if there is allot of activity and the recording has to play allot.

Another timer option would be to use one of these. That is if you have a plug outside in the area. Then you could use a wall-wart to power the whole project and the timer would control when the power is turned on and off. http://www.aquacave.com/single-heavy-duty-br-programmable-timer-br-by-hamilton-technology-2247.html

Overall they both cost the same. But with this rout you are able to cut the high cost of solar panels and batteries. Not to mention any kind of controller you would need to regulate the batteries as they charge.

Thanks for the ideas. What do you guys think about this solar panel?

http://www.adafruit.com/index.php?main_page=product_info&cPath=35&products_id=200

Well it all depends on your charging controller which depends on what batteries you plan to use.

The DS1307 is popular for applications that require keeping accurate real time.

When shopping for solar cells, keep in mind that the voltage is usually spec'ed for ideal sunlight conditions, which you'll only see for a short period even on the best of clear days. That's why panels for charging 12V lead-acid batteries are typically 18V arrays: you need a higher voltage than the battery being charged, and an 18V panel will give you that even under less-than-ideal conditions.

So you need to pick your battery before you pick your solar panel, in order to know what voltage to choose. You also need an estimate of your load current, to select the current rating for the panel and the capacity of the battery. You'll want a panel rated at least 4-5 times the load current, so it can power the load and charge the battery even on a cloudy day. In this case, you can probably ignore the power requirement of the sound device, because it'll only be running for a few minutes per night. Focus on the requirements of the Arduino, and consider buying a kit so you can build it without the power-indicating LED.

Great info. Thank you all. Yes, the solar capability will require the most thought. I'm going to save this part for last.

Richard...I was also thinking about collecting the data (hits) to view the activity. 8)