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Topic: Solar Powered Arduino with Speaker and Battery Backup (Read 3700 times) previous topic - next topic


I am planning to build a small device too scare off the deer that keep eating all my flowerbeds.

For background info, I am using
2 PIR motion sensors
a photoresistor to identify night/day
a SD card/reader
LM386 audio amplifier
6V 100ma small solar panel, a diode
7.4V 1000mAh LiPo
I plan on it being about the size of an aluminum can. The program is simple, only if it is at night and motion is detected then a WAV file is triggered to play from the SD card. I would like the volume to be comprable to those little brookestone pop-up speakers http://www.brookstone.com/mobile-mini-speaker

Here's my question. I am unsure about charging a battery that is powering the circuit at the same time. Is it even possible to add any charge to a battery of that size with a panel that small? If it is, I know I need a diode to prevent the panel from sucking current at night but I am also figuring that the voltage from the battery has to be checked periodically and the voltage in from the panel must be stopped once the battery is full in order to prevent damage to the battery. I am also a bit lost on what kind of speaker will give me some good volume and decent fidelity without breaking the bank. I found this ebay one that fits the size requirements but I need hear some second opinions. http://www.ebay.com/itm/Brand-New-2-2-inch-Neodymium-Full-range-Speaker-From-IDN-Panasonic-/221115532729?pt=US_Radio_Comm_Speakers&hash=item337b8345b9

1. To stop from overcharging, would I use a little DC-DC relay to accomplish this or is there a better way? Or is this such a small voltage that none of this is even necessary?
2. Is this a good speaker option? What would be a better one?

I know I haven't thought of something or what I think I know is wrong, so please, steer me in the right direction!


6V 100ma small solar panel, a diode
7.4V 1000mAh LiPo

You need SEPIC Constant-Current/Constant-Voltage Battery Charger circuit - LT1512.

LT1512, Digikey, $6.78



I think your project would be much simpler if you use a decent sized lead-acid battery. With a small solar panel you would probably need no regulator circuit just the diode to ensure the battery doesn't discharge inot the panel.

Whatever battery you use you will need a solar panel that produces more volts than the battery voltage. You will also need to estimate (and be pessimistic!) how many milli-amp-hours your circuit will consume in 24 hours and how many mAh the solar panel will produce taking account of whatever local weather conditions affect the amount of sunshine. The battery has to have enough capacity to deal with a succession of days of poor sunshine. If you need the device to work in winter you will have to take account of the shorter days (less sun) and longer nights (more Arduino activity). That will need a much bigger solar panel than you would need in summer time.

Try a second-hand 12v car battery?

Two or three hours spent thinking and reading documentation solves most programming problems.


Thanks for the info, seems like the little solar panels are not going to work out for now.

Any comments on the speaker?


The speaker use at outdoor and need weather proof. Here is the Plan B;-

Insignia™ - Simulated Rock Outdoor Speakers (Pair)

$40.00 for each,  You need only one per setup since the deer would not be enjoy stereo sound.

Outdoor Speakers (Pair), Bestbuy, $79.99


No no no no, I have new plan to weatherproof things. Instead of buying high cost outdoor equipment, Im going to coat the circuit,the speaker, wires, basically everything in a new spray called NeverWet. I highly suggest a youtube search. By spraying the speaker/mic, dock and headphone holes, they made an iPhone work underwater. It is some impressive stuff. Now anything can be weatherproofed or damn near waterproofed.



Did you ever build this device?  I have a similar concept that I've begun working on.  I would love to hear whether or not your worked.  Mine is a bit more complex perhaps because of a mesh/NW type architecture that will allow multiple devices to communicate with each other to determine the best method and location to scare the darn deer away (depending on which direction the PIR senses the motion from).  My plan is to use multiple attachments that do different tasks to ensure that the deer do not get used to the affect and disregard it.



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