power demand on arduino camera trap project

Hi,

I've been using an Arduino Uno board to run a camera trap. The input to the board is a parallax x-band motion sensor (powered via the board), and the outputs are the focus and shutter controls on my camera. I run the board on a 12V SLA battery. Everything works great, I now have two camera traps set up and I love the pictures I've gotten. The only issue that I use up a lot of power--I require a 45ah 12V to run my camera trap for ~2 weeks--hiking my camera into remote spots is a pain when I have to lug a car battery along with me.

Does anyone know how I could make this setup more power efficient? I can't put the system to sleep, because it needs to be constantly monitoring in case a critter shows up (they show up at all hours). Would switching to the Arduino mini save power? I heard it's more efficient, but the spec sheet looks the same and I'd have to step down the voltage from my 12V batteries to power it. Any thoughts on how I could significantly increase my power efficiency?

Thanks a lot.

JonnyA: Hi,

I've been using an Arduino Uno board to run a camera trap. The input to the board is a parallax x-band motion sensor (powered via the board), and the outputs are the focus and shutter controls on my camera. I run the board on a 12V SLA battery. Everything works great, I now have two camera traps set up and I love the pictures I've gotten. The only issue that I use up a lot of power--I require a 45ah 12V to run my camera trap for ~2 weeks--hiking my camera into remote spots is a pain when I have to lug a car battery along with me.

Does anyone know how I could make this setup more power efficient? I can't put the system to sleep, because it needs to be constantly monitoring in case a critter shows up (they show up at all hours). Would switching to the Arduino mini save power? I heard it's more efficient, but the spec sheet looks the same and I'd have to step down the voltage from my 12V batteries to power it. Any thoughts on how I could significantly increase my power efficiency?

Thanks a lot.

Well converting to a bare bone type 328p board might help because you would not be powering the USB serial converter chip, the power on led, and the poor efficiency of the on-board linear 5 volt regulator. Find a switching mode 5 volt regulator and that should cut your continuous current draw maybe in half or more. After that using various AVR sleep mode might save more, but that would probably involve a rewrite of your code to make sure the sensor can 'wake-up' the avr chip and execute your program.

Lefty

Nick Gammon wrote a tutorial for achieving low power on Arduino class machines. It might be you can't go into a deep sleep, but hopefully you can save a reasonable amount of power: http://www.gammon.com.au/forum/?id=11497.

what is using the most power? the 'duino or the motion sensor

also, could you attach a solar panel to keep the battery topped up?

Thanks for the prompt feedback. I'm pretty sure the Arduino is hogging the power, since the sensor's listed power supply is 8mA, and I'm drawing roughly 100mA (burning through a 45ah 12V in two weeks), I think I calculated that right...

So I think I'll try the Arduino Pro Mini -- can anyone recommend between the 3.3V vs. 5V? I think the x-band sensor works with either, but I'm not sure what the functional difference would be. [http://www.parallax.com/Store/Sensors/ObjectDetection/tabid/176/ProductID/606/List/0/Default.aspx?SortField=ProductName,ProductName].

I read through the linked tutorial on cutting power consumption. I'm having trouble understanding what exactly it means to put the board to sleep. Is it possible to have the motion sensor actively sensing for motion, but also have the board in some sort of power saving mode?

Thanks again for the feedback, I appreciate the help.

How are you reducing the voltage from 12v to 5v? If you aren't using a UBEC voltage reducer, you might want to try one to save power.

I just run the 12V power leads to a barrel connecter and plug to the Arduino, then power the sensor from the Arduino. Would it be more efficient to power the sensor through a separeate 12V-5V stepdown? I have some murata DC-DC converters hanging around, so I could try that. Thanks

crikey you are probably burning more power in the on board voltage regulator than anywhere else!

can you use a 6 volt battery (I recall seeing 6 volt lead acid somewhere)

either that or a more efficient (switching) voltage reulator to provide 5 volts for the 'duino or even 3.3 if you can get away with that

It's not clear to me why it would be especially wasteful to use the Arduino to regulate the voltage (I'm a biologist and can barely work my TV remote, so bear with me :)). So it would be more efficient to find a different DC-DC converter and use that--like a 12V-5V or 6V-5V? What is it about the Arduino volatage regulation that makes it inefficient compared to other methods?

Thanks Jonny

JonnyA: It's not clear to me why it would be especially wasteful to use the Arduino to regulate the voltage (I'm a biologist and can barely work my TV remote, so bear with me :)). So it would be more efficient to find a different DC-DC converter and use that--like a 12V-5V or 6V-5V? What is it about the Arduino volatage regulation that makes it inefficient compared to other methods?

Thanks Jonny

simple really

start with a normal regulator you feed 12 volts in take 5 volts out so there's 7 volts across the regulator let's say 100 mA current that's 700 mW burning off in the regulator!

this is not a feature of the Arduino regulator it's a feature of regulators

a switching regulator is smarter uses electronic wizardry to only take what it needs to keep the 5 volts ouput

I would still seriously consider a 6 volt battery as the power source

Here’s an example of a small, self-contained 5 VDC switching regulator that could handle any voltage from a realistic battery pack (and many common small solar arrays as well). Theoretically, one could replace the on-board linear regulator with it, but given the level of technical prowess (or lack thereof :wink: ) JonnyA admitted to I wouldn’t recommend it in this case. Instead wire up the output to the 5V pin. You can do this since this is a regulated power supply. Don’t do this with an unregulated supply, like batteries, even if the nominal voltage is around 5 VDC.

It should be possible to keep the sensor awake and allow the Arduino to sleep. This can be done 2 different ways. How often do you need to check for an animal running past? Every 1 seconds? Then check for sensor input every 1 second, or use an interrupt. This will allow your battery to last 10x longer or be 10x smaller.