Another idea: Solar-Powered Camera

[jjcme101]

Thanks to everyone who offered advice on my last idea about solar-preheated domestic water.

Another idea I'd like to implement is a solar-powered webcam. I have an IP camera that uses (according to my kill-o-watt meter) a max of 2 watts (it's a 5v dc camera). I'd like to run it off a battery and use a solar panel I already have to keep the battery charged. The panel in question is a 12v 20 watt panel. If needed, I can use a timer to shut the camera off at night and only run it during the day.

I'm eyeing this charge controller:

http://www.amazon.com/Sunforce-7-Amp-Charge-Controller/dp/B0006JO0XI/ref=sr_1_sc_1?ie=UTF8&qid=1339420617&sr=8-1-spell

And of course, a 5v regulator:

http://www.radioshack.com/product/index.jsp?productId=2062599

Is this project feasible? Any recommendations on what battery I should buy? Do I need a larger solar panel? I live in Northern Maine. And if you could include an equation to support your answer that would be much appreciated!

Thanks again!

[Sunking]

I am being lazy today but I see some problems, mostly in the 7805 regulator. The 7805 is a series voltage regulator. What that means is the Input Current = Output current which is real bad news for solar systems. That is why PWM controllers suk.

OK you camera use 2 watts @ 5 volts which means the current is .4 amps. So the battery is @ 12.5 volts supplying .4 amps to the 7805 regulator, and the regulator output is 5 volts @ .4 amps. See the problem?

Well here is the problem your battery is supplying 12.5 volts x .4 amps = 5 watts, while you are only using 2 watts. That means you are burning off 3 watts on the regulator as heat. No problem for the regulator as it is designed to do that but is a huge waste of energy.

Normally one would calculate the camera daily usage as 2 watts x 24 hours = 48 watt hours. However that is not a true statement because the real consumption is 5 watts x 24 hours = 120 watt hours.

If you were to use 48 watt hours and your area Solar Insolation is 3 sun hours in winter you would use a 30 watt solar panel, and a 12 volt 20 AH battery. When in reality it should be a 80 watt solar panel and a 50 AH battery.

So if you used the 48 watt hour figure to design by, it would fail on the 2nd or 3rd day never to come back on.

[billvon]

Is this project feasible? Any recommendations on what battery I should buy? Do I need a larger solar panel? I live in Northern Maine. And if you could include an equation to support your answer that would be much appreciated!

One suggestion. Do not use a 7805; use a switching supply instead. They are way more efficient. Here's one that's fairly cheap:

http://www.digikey.com/product-detail/en/OKI-78SR-5%2F1.5-W36-C/811-2196-5-ND/2259781

Also you might consider a charge controller with a built in LVD so that the battery disconnects when it gets too low; it will save you some $$ for new batteries.

[jjcme101]

So if you used the 48 watt hour figure to design by, it would fail on the 2nd or 3rd day never to come back on.

So, assuming I used the more efficient regulator suggested by Billvon (thanks), what size panel would I need to make this work?

Maybe I should think about burying a power cable

[Sunking]

So, assuming I used the more efficient regulator suggested by Billvon (thanks), what size panel would I need to make this work?

What is the location and time of year use? Need a zip code or city.

[jjcme101]

zip is 04769. Thanks!

[Sunking]

zip is 04769. Thanks!

Maine huh? Not good.

Panel wattage = 120 watts
Battery Capacity @ 12 volt = 50 AH (AGM format, FLA will not work for this application, charge rate too high)
PWM charge controller AMPS = 10 Amps

FWIW if located in Tuscon AZ

Panel wattage = 30 watts
Battery = 50 AH
Pwm Charge Controller = 5 amps.

[jjcme101]

Nope, not good at all. Guess I'll invest in a cable to power the camera. Thanks for figuring that out though.

And I guess I'll demote the current 20 watt panel I already have to running a homemade solar heater for my daughter's swimming pool. It seems to pump water pretty well with the 12v bilge pump I have it hooked up to.

[Sunking]

And I guess I'll demote the current 20 watt panel I already have to running a homemade solar heater

Huh? A 20 watt panel can only heat up a cup of coffee in a day. Trying to heat a pool with a 20 watt solar panel is like pissing on a forest fire.

[inetdog]

Huh? A 20 watt panel can only heat up a cup of coffee in a day. Trying to heat a pool with a 20 watt solar panel is like pissing on a forest fire.

"Running the solar heater" = powering the pump in a solar heat system, not supplying the heat itself. Still not clear how much water a 20 watt pump can move though.

[jjcme101]

Yes. My 20 watt panel powers a Rule 360 Bilge pump to move water through a homemade collector to heat the pool. It's just a little inflatable kids pool. The water flow seems pretty good. My collector is just some garden hose pained black. I'll probably add some glazing and more hose to it soon.

Could I put my 20w collector to better use doing something else?

[inetdog]

Could I put my 20w collector to better use doing something else?

Float charging batteries for emergency lights, etc? Keeping the battery for something like a boat or lawn tractor healthy during the off-season?

[alexadam1212]

nice power energy-conservation ip cameras,i often buy bull **** (mofified by Russ) in handgiftbox before,so i need to search some solar-cameras now.lol
Mod note - next funny link you are gone.

[bcroe]

Switching regulator

One suggestion. Do not use a 7805; use a switching supply instead. They are way more efficient. Here's one that's fairly cheap:

http://www.digikey.com/product-detail/en/OKI-78SR-5%2F1.5-W36-C/811-2196-5-ND/2259781

Also you might consider a charge controller with a built in LVD so that the battery disconnects when it gets too low; it will save you some $$ for new batteries.

Switching reg is the way to go; might take some noise filtering on the power leads. DIGIKEY does
quality stuff and a lot of my supply. But likely a running switcher can be picked up for like $3 on
Eb+y, check it out. Bruce Roe

[share2jason]

good idea

good idea, would be great if can work on my IP Camera...