Can the Alarm Battery power the Raspberry Pi

[jscherer26]

I was wondering if I would be able to power the raspberry pi somehow via the 12v battery that backs up my alarm system. I was thinking this may act like a UPS for my raspberry pi. Maybe just wishful thinking, but I lose power now and again and I was just going to buy a standard UPS for the AD2PI Network Appliance and it made me wonder. Heck, I'll get an email from the alarm telling me it lost power, so I'd have time to ssh to the raspberry pi and shut it down. Any thoughts?

[mathewss]

I have been working on a project to power the Ad2Pi from the panel DC battery OR directly from the AC Adapter and so far it has been working perfectly running for a month or more now. I have not tested with the battery but I see no reason why it would not work. I will try and post pictures but for now I will just describe what I have done. The design I used will work connecting to both a DC or AC power source from 5v to 30v.

I took a RioRand LM2596 I got a few from Amazon for a few dollars each.

I then cut apart a Mini USB cable to expose the red and black power wires and attached them to the RioRand output noting the polarity was correct.

I then soldered together a simple full-wave rectifier bridge with 4 diodes on a 1/2" square piece of prototype board. I connected the DC output of the bridge to the DC input of the RioRand and the AC side of my bridge circuit to the AC terminal blocks on the panel.

I then powered up the panel and connected a volt meter to the output of the RioRand and adjusted the potentiometer till it was at approx 5.1v. It required a LOT of turns to get it down.

I then sealed the whole thing inside of shrink tubbing so it would be electrically safe inside my 20P test panel.

I then connected the USB B connector to my AD2Pi that is mounted inside of the panel box and did a smoke test and the Ad2Pi booted right up.

Some issues to watch out for.
The RioRand produces some RF noise as it is a buck boost design but it seemed minimal and did not seem to conflict with the 58xx radio inside of my panel box. If the RioRand it is overloaded it will fry as it does not have a very good built in protection circuit.

The good stuff.
It produced only a tiny amount of heat and is 89% or more efficient. The Pi uses from 500mA to 800mA and the RioRand can do as much as 3000ma a nice safe amount of overhead. With the added bridge circuit I can use it on DC and AC from 5 to 30v with only a little loss of efficiency in the diodes voltage drop.

What I have not tested "yet" is power via the battery. My only concern would be that it may effect battery charging but it should be easy enough to find out and run some tests seeing how long things will run on only DC power and how fast the battery charges back up.

In your case with just DC you wont need the bridge and can connect it directly to the battery terminals and gain a few percent of efficiency.

Re
Sean M

[recurry]

I run the RPI that interfaces my 128BPT to my lan from the panel's 12v using a small switching powersupply that is used for radio control aircraft. Unfortunately it's about a $30 unit however I recently picked up a very robust switching powersupply from Goodluckbuy.com for about $6 that I will be swapping it out. While the DIY approach that Matt is using may be a bit less expensive I prefer the switcher as it's quite a bit more efficient and the panel has very little current capability - especially if you have more than a couple of keypads or other devices that run off the panel's "Aux" output.

Ron

[jplee3]

I was curious about this too but. Sean and/or Ron, can you guys post some pictures of your setups? I'm most interested in powering the Raspberry Pi from the alarm panel itself - is this possible or is the voltage too low?

What would make the most sense here as a more 'integrated' approach? I have the ad2usb and just got a Raspberry Pi. Haven't had the chance to connect them all together and I'm still waiting for the Edimax wireless adapter anyway. Just trying to figure out the easiest/least painful way to connect things up. I'm not much of an electrician and am pretty lost and confused when it comes to voltage and getting components to work together on the proper voltages, etc....

[jplee3]

Ron,
Just re-read your post and saw that you got a $6 switching power supply? Which one did you buy, specifically from that site (link?) and how did you end up connecting it to the panel and Pi? Based on your response, it *sounds* like you just connected it as you would another keypad and then wired the PI to it?

Any help would be appreciated.

Thanks!


BTW: Did some searching and stumbled across this guy - http://www.dx.com/p/dc-6v-24v-to-usb-dc ... 8ggnfldVkZ

That seems like it might do the trick no? Just run power +/- from terminals 4-5 on the Vista 20p to the two terminals (sounds like this produces 12v output e.g. for keypads,etc) on this unit and simply plug the Pi into the onboard USB port. Seems super easy and like the perfect solution assuming it actually would work.

[mathewss]

The problem with using the DC terminal blocks 4 and 5 is that the current drain from the Pi will exceed the amount the panel can supply resulting in your other keypads or devices on the bus having problems or shutting down especially when the alarm is going off and the siren is on.

I used this device and added a bridge rectifier to convert the 16v AC supply terminals to a 5v DC supply.
http://www.amazon.com/RioRand-LM2596-Co ... =pd_cp_e_1

I then attached a bridge rectifier using 4 1w diodes to the input of the LM2596 to convert the AC into DC.

bridge.gif

The transformer can supply a lot of watts but I have not crunched all the numbers to give a rating of max power consumed using this method but my rough estimates show no concerns of having any power shortages.

The other option that seems very reasonable is to simply attach the LM2596 directly to the battery with no bridge circuit but I have not tested if the battery charging circuit can provide enough continuous watts. The only concern would be to overload the charging circuit and possibly damaging it or preventing the battery from being charged.

Re
Sean M

[mathewss]

Just an update on this project. Last night we connected our Ad2Pi directly to the battery through the buck boost circuit board with the rectifier still attached causing a small amount of voltage loss. It lasted 21 hours on DC battery with a 7ah batter. It is now charging the batter and already at about 12v in just a few hours.

PiPower.jpg

Re
Sean M

[wilsonb]

Great news..
I really like the fact of connecting it to the battery and having backup power to the Pi.

OK, so the final result is...?
Buy RioRand LM2596 DC-DC Buck Converter , adjust the pot down to 5.1V and connect (via USB) to Raspberry Pi?
No Diodes(rectifier) needed since it's DC already, right?

[kevin]

Correct, battery is DC, just buck down to 5v from 12v.

[wilsonb]

Ordered...

Thanks..