Low Power Blinker

[RKJM]

Hi All,
I am looking for some input on which controller I should use for an LED project I would like to build. The project will need to sense when it is exposed to a bright light (flashlight) and will output a code in IR. I built one using a Adafruit BoArduino and it works great. The problem I have is that the project will be outside and in an area where this is no power hookup (mounted high in a tree). I don't want to have to climb the tree every few weeks to change batteries. Any suggestions would be greatly appreciated.

Have a great day!

Bert

[chatham]

Hmm... I guess my immediate question is going to be, have you been able to make something so far that doesn't react to sunlight? As long as you can get it so the input isn't being continuously activated, any of the AVRs (including Boardunio) can be put into a low-power state that uses tiny amounts of current (the power-down mode on the ATmega328 uses 0.2 microamps) and then you can wake up the chip with an external interrupt. With some AA batteries at 1200mAh, that would basically run your sleeping AVR for years. The tricky part will potentially be your sensor... Is it an active component, or just a photo-resistor? If it's a photo-resistor, you could use that to activate the wake-up interrupt, and when the AVR wakes up, it sends the IR signal and goes back to sleep.

[brucef]

Yeah, presumably you'll have to use a reasonably accurate clock to keep the thing turned off during the day, or something like that, in order to keep it from draining the power completely in daylight hours.

One consideration for your power supply is operating temperature range; how cold do you expect this thing to get and continue to operate properly? For low current and low temperature, I'd probably look at lithium batteries, and just size up the battery pack until you get the length of runtime you're after.

[RKJM]

I am using a photo cell for the trigger. It is shielded from the sunlight and seems to stay off during the day light hours. I am intereseted in the clock idea though. I will look into that. The device will be in high in a tree with temps ranging from -20F to 110F. The project is for another hobby of mine, Geocaching.
Thank you for your the responses.

[chatham]

Another thing to be aware of, higher clock speeds mean more power consumption. So you'd need to migrate away from the BoArdiuno, or at least get an external programmer to change the fuse bits to lower the clock rate the chip is running at, and set the CLKDIV_8 fuse.

[scott_42]

Geocaching

You have my attention now. Since I don't do any caching at night and I don't know anyone that does (lots of parks close at sunset), are you planning on this working during the day too somehow?
Is this going to be a multi-stage puzzle chain?

Lbh pna EBG13 lbhe uvagf gb zr. YBY

Also if you are just looking at a simple light sensor and outputting an IR signal, you don't need a full BoArduino out in the wild. You can use something much smaller like an ATtiny chip. With a LiPo battery you can probably run it a year in between recharges. Are you putting it in a little Pelican or Otter box or do you have some other NEMA4 enclosure to keep out the elements?

[RKJM]

Another thing to be aware of, higher clock speeds mean more power consumption. So you'd need to migrate away from the BoArdiuno, or at least get an external programmer to change the fuse bits to lower the clock rate the chip is running at, and set the CLKDIV_8 fuse.

Thnaks, I will look in to that. I was planning on just wiring up a socket with only the needed hardware to run the micro, LED and cell and not a complete BoArduino. I am very new at this and need all advise I can get. Thanks for the input!

[RKJM]

Geocaching

Is this going to be a multi-stage puzzle chain?
Lbh pna EBG13 lbhe uvagf gb zr. YBY

Ab uvagf ab guve zhyg sbe abj.

I plan on putting the whole thing in a 2 liter pre-form. You can run them over with a truck and they won't break. This will part of a multi that will be only be able to be solved at night.