UPS compatible with OpenSprinkler Pi v1.4

[Matteo]

Hello!

I own a Raspberry Pi and I want to buy the OpenSprinkler Pi.
I’ve read in the Raspberry Pi FAQS web page that failure to properly switch off the Raspberry Pi may corrupt the SD card and it will be necessary to re-image it.

On average, there is a power outage twice a month in the house where I live because my mother switches on too many appliances at the same time 🙁 .

In my case, I guess it is highly recommended to use an UPS to keep the Raspberry Pi always running.

I’ve found this one: http://www.piups.net but I guess it can’t be installed between the Raspberry Pi and the OpenSprinkler Pi v1.4 board because there isn’t enough room.
Question n°1: it it true that it can’t be installed, please?

A truck battery (12V 120Ah 700A) is available and always kept charged in the room where I want to install the OpenSprinkler Pi v1.4.

I found this DC power supply module in ebay:
http://www.ebay.it/itm/NEW-DC-12V-24V-40V-to-5V-4-USB-Step-Down-USB-Step-down-Power-Supply-Module-UK-/271507275363?pt=UK_BOI_Electrical_Test_Measurement_Equipment_ET&var=&hash=item3f37183e63
I could connect the power supply module input to the truck battery and the output to the Raspberry Pi micro-USB.
Question n° 2: I wonder if it can work as UPS just for the Raspberry Pi.

In normal conditions (i.e. NO power outage), the Raspberry Pi would be powered by the OpenSprinkler Pi v1.4 via GPIO pins and by the power supply module via micro-USB.
Question n°3: which energy source would be used by the Raspberry Pi, please?
1: only GPIO pins
2: only micro-USB
3: both

Thanks in advance for any reply!

Bye.

Matteo

[Ray]

Question n°1: it it true that it can’t be installed, please?

Actually I think it can. The OSPi 1.4 enclosure does not fully expose the microUSB port, but you can always use a dremel or even a diagonal cutter to enlarge the opening so that you can insert a micro USB cable through the enclosure.

Question n° 2: I wonder if it can work as UPS just for the Raspberry Pi.

Looks fine. It’s not clear to me whether this is a switching regulator or a simple linear regulator. If it’s linear, the efficiency will be pretty bad and it will dissipates a lot of power in heat.

Question n°3: which energy source would be used by the Raspberry Pi, please?

I have not checked the Raspberry Pi schematic so I don’t know how it works when you have multiple power sources. My guess is that it has internal mosfets to select a single power source if multiple are present. But in the worst case, you can always use a Schottky diode connected in series with one power source to avoid two power sources competing with each other.

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