12v to 5v/usb convertor?

[w1z4rd]

Im busy setting up a solar powered pi. Basically its going to be a webserver/webcam Pi powered by two of those 12v batteries alarm systems and gate batteries use. I am going to feed the batteries with 12v trickle charge solar panels.

Where would I find something like the converter I would need that would drop the voltage and power the pi through its usb port? I have a feeling that I am going to need to hunt down an electronics expert and get it custom made

Also, does anyone know a good place (online) to order some 12v trickle charge solar panels?

 

[Messugga]

Won't be that major actually. Essentially you just need a 5V voltage regulator that can handle the current with a heat sink for it. Any electronics place should be able to help you out. You'll want to fuse it as well. Google for the circuit, should be plenty available.

 

[GPS]

Ebay. Search for 12v to 5v converter. I'm using 1 myself in a solar setup for powering a cell router via USB.

 

[upup]

chaepest would be to buy a car 12v to cell charger. R30. But rather build your own with a fuse and good heat sink. Or buy a project kit from electronics123.

 

[bdt]

He means a 7805 regulator, or you could (should?) use an LM317. Either way, you give 'em a chunk of metal to sink heat and something for the weather. Oh, and some easy way to handle the fuse.

 

[dillinger]

If in Joburg give Current Automation a try, they do solar, batteries, charger, inverters, power supplies and DC-DC converters.

http://www.rectifier.co.za/Meanwell/dcdc_module.html

 

[Vis1/0N]

He means a 7805 regulator, or you could (should?) use an LM317. Either way, you give 'em a chunk of metal to sink heat and something for the weather. Oh, and some easy way to handle the fuse.

12V in , 5V out. With the linear regulator (7805, LM317) you are getting less that 50% efficiency. Assuming 500ma you would be using 2.5W to power the Pi, you are losing 7V*0.5A = 3.5W. A single 12V battery is probably rated 7AHrs, which gives under 14 hours continuous (ab)use. The solar cells need to do quite a bit of work to keep up, trickle chargers won't cut it. Ideally you need to use the 12V battery as back up, and power as much as possible from the solar cells that could have higher that 12V voltage.

You would need a smps (switching regulator), which is much more efficient at 75% to +90%. Those $2-3 DC-DC converters on ebay are a lot better that a 7805.

 

[ginggs]

http://www.takealot.com/electronics...ar-charger-2-1a-for-ipad-iphone-ipod,11008227

 

[bdt]

12V in , 5V out. With the regulator you are getting less that 50% efficiency. Assuming 500ma you would be using 2.5W to power the Pi, you are losing 7V*0.5A = 3.5W. A single 12V battery is probably rated 7AHrs, which gives under 14 hours continuous (ab)use. The solar cells need to do quite a bit of work to keep up, trickle chargers won't cut it. Ideally you need to use the 12V battery as back up, and power as much as possible from the solar cells that could have higher that 12V voltage.

Okay, so that's the 7805 roundly trashed; is the 317 as dire? Also, the dc-dc converters dillinger mentioned, are they more efficient?

 

[Richardxtc]

http://www.selectsolar.co.uk/cat/27/solar-cells-6v-154v

could this work? or is the amperage to little?

 

[ginggs]

Okay, so that's the 7805 roundly trashed; is the 317 as dire?

Yes, the 317 is also a linear regulator.

Also, the dc-dc converters dillinger mentioned, are they more efficient?

They look like switching regulators, so yes.

 

[sajunky]

chaepest would be to buy a car 12v to cell charger. R30. But rather build your own with a fuse and good heat sink. Or buy a project kit from electronics123.

I just dismatled my car charger (sold on the street). It has switching mode converter. No radiators required. Yours can be different.

 

[kayvee]

+1 for the ciggie lighter type chargers, cheap as chips.

Okay maybe not 90+% efficient, but they are switchers so you should be good to go.