Trying to build my own UPS for my alarm system

I am building my own alarm system based on Arduino UNO and some reed switches , and some PIR Sensors.
The main power will be 12VDC, for Arduino Uno 5VDC

I am thinking of an DIY UPS for this alarm
I plan to plug a 220V AC => 14VDC adapter connected to that module


The module will be connected to the adapter, connected to a battery, and connected to my alarm system
So my alarm system should be secure for a short period of time if the main power is cut.

What do you think of my solution ?
What kind of battery can i use ? (in term of battery technology and power)

Finally, i would like to plug a relay of something on the output of the adapter (220VAC to 14VDC) and plug it to my arduino and thus be able to receive an alert if the main power fail !

Please advise me ? how can i do that kind of relay or device ?

thanks a lot

Your post was MOVED to its current location as it is more suitable.

hello thx and sorry

The UPS for my Raspberry Pi uses a 12V LiFoPo4 6Ah battery.

I use a LiFePo4 charger like this one,

The charger connects to the LiFePo4. The LiFePo4 is connected to a 5V regulator, like this one:

The regulator, which has output filter caps, is what powers the RPi.

I've ran the RPi for 8 hours on battery.

I use this battery:

I use this case to hold the battery:

great where did you buy this ups ?
where did you buy the case?
One important, thing, when your pi is running , and suddenly the main power is cut
normaly the pi go on working on the battery ?
it is diruptive to move from main power to battery ?

The setup I explained above, the RPi is always running off the battery.

The Charger, feels the battery volts. If the battery is at, in this case, 13.8V or more, the charger shuts off charging mode. When charging mode is shut off the RPi is being supplied by the battery. As the charge on the battery drops, the charger, at a set point, starts charging the battery again. This cycle continues.

All those components came from Amazon.

It is not disruptive to move from main power to battery.

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A link to the case:
SNTNICTR 125 x 125 x 100mm (5 x 5 x 4 inches) Electrical Project Case Junction Box IP65 Waterproof ABS DIY Power Outdoor Enclosure Gray - - AmazonSmile

The battery:
AmazonSmile: 2000 Cycles 12V 6Ah Miady Lithium Iron Phosphate Battery, Rechargeable LiFePo4 Battery, Low Self-Discharge and Light Weight, for Kid Scooters, Fios Replacement Battery : Automotive

AmazonSmile: 14.6V 5A Charger 12V 4S LiFePO4 Battery Pack Charger 14.6V Charger 12V Smarrt Charger with Clips(12V 5A Charger) : Health & Household

AmazonSmile: DC 12v 24v to 5v Step Down Converter Regulator 5A 25W Power Adapter Reducer for Car Electronics Truck Vehicle Boat Solar System (Accept DC 8-40V Inputs) : Electronics


Most of the smaller alarm systems just use a small sealed lead acid battery which is supplied with a regulated ( float ) voltage from the mains to keep it charged .
The battery then feeds the alarm - simple and cheap .

Transformer >diode bridge and capacitor > 7805 with zener in ground connection to get 13volts for the battery

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