Power Sensing & Power Backup

Hello, I'm building a controller for my reef. Until now, everything is working great: relays control, dosing pumps, temperature, pH etc.

My next 3 things I would like to add to the controller are: 1. Backup battery for the controller 2. Identify when AC power is lost 3. Send SMS for every special event in my reef.

For now, let's focus on the first 2 things.

For the first thing, I found that http://www.seeedstudio.com/depot/lipo-rider-p-710.html?cPath=155. Can you please help me understand if and how it can help me? How exactly can I connect it to my Arduino? (I have zero knowledge in electronics...)

How can I implement the seconds thing?

P.S Both, Arduino and pH circuit is working on 12v.

Thanks! Danofri.

The simplest solution to 1) and 2) would be to buy a commercial battery backup unit (like from APC, etc). The LiPo rider only supplies 5V at 350ma; I'm guessing your controller eats a bit more than that. It's not too hard to find commercial battery backups that also have a serial port which you can use to detect when the power goes out. Granted, monitoring when the power goes out is a bit of a moot point -- you can't send any messages when this happens because... the power is out. :~

With respect to triggering SMS messages from your Arduino it would be simplest to have a USB cable between the Arduino and a computer with a programming running on the computer listening for messages. If you can provide some detail as to what operating system you use and what programming languages you are familiar with then someone can probably point you in the right direction on setting up that monitoring. If that sounds undesirable then you can get an ethernet shield for the Arduino to create a standalone kind of unit.


Do you mean a regular AC UPS? I though using somekind of DIY DC UPS.

Regarding the messages, I know that I can not send messages when the power is out, this is why I wanted the battery pack :)

I'm going to connect an old sony ericsson to the Arduino, or GPRS shield.

Many thanks!! Danofri.

It is easy enough to use a very basic 5V “wall wart” type power supply as a mains voltage detector. Connect the 5V to an Arduino digital input pin. When the 5V disappears, that means the the power mains have failed.

Yes, that would work fine, however be sure to wire a pull-down resistor to the digital input pin to be sure that the unpowered +5vdc does not present a ‘floating input’ to the pin when the AC power goes out. I’ve seen many 5.1 regulated ‘cell phone’ chargers in thrift stores for around $1 each that would work well.


everything is working on 220V, only the Arduino is working on 12V DC. The only thing I want to run when the main power is out is the Arduino. It is OK for me that the Arduino will send me the SMS and will shut down. I just want to know about a power outage and when the power is coming back.

retrolefty, can you please explain me the potential problem and solution? I didn't understand (almost zero electronics knowledge :))

Many thanks for the help!

KE7GKP: Do you mean "when the power is coming back"? Or do you mean "when the power comes back"? The first would involve using a crystal ball to predict the future. The second would be simple to do so that it sends out a message upon power=up. If you had an RTC (Real-Time Clock) in the system somewhere, you could even keep track of how long the power had been out.

The second options of course :) (I'm sorry for my English).


Can I use 78L05 regulator ?

Input leg will be 12V. GND will be the GND from the 12v. Output will be connected to the arduino digital pin.

Will it be OK?

Thanks! Danofri.

Not to get argumentative about using a UPS but it shouldn't be hard to find a UPS system that includes a serial port to detect when power goes out. I know there's open source software out there for Linux (apcupsd for APC brand) that would detail the protocol used. You could also do some simple rigging that would read a digital signal from any of the status LEDs on these units.

Don't forget there's no requirement to use the AC outlets on the unit; you could attach to the battery directly if you're looking for efficiency.

Then just read the voltage from the status LED.