Creating an "long life" LED flashlight for underwater triggercam

[Jesse the Biologist]

Hey folks, I've been working on a underwater camera trap (think game camera for octopus). It's mounted in an underwater housing and uses far red light to detect and photograph octopus when they come and go from their dens. I've noticed it drains the battery significantly to run the far red LED's all the time in order for the camera to detect when octopus come and go, in order to remedy this I decided it would be prudent to build an independent lighting system that can be deployed along with the camera. All I need is for the battery or battery pack to last ~24 hours and run one 6 volt 200 mA LED on a starboard. I'll attach a switch into the circuit that can be operated outside the housing to allow the light to be turned on inside its waterproof housing once deployed. If anyone has any ideas they would be much appreciated. Simple is best. Thanks for the help.

 

[BradtheRad]

Suppose you turn on the led once per minute, briefly? And if motion is detected then let it shine while you run the camera?

Or if you're talking about a remote-control switch, then a radio transmitter and receiver is probably what you need. The receiver can be a pocket radio

Or if you're close to the camera, then the remote signal can be either: a) audio tone, or b) light beam.

 

[Jesse the Biologist]

Suppose you turn on the led once per minute, briefly? And if motion is detected then let it shine while you run the camera?

Or if you're talking about a remote-control switch, then a radio transmitter and receiver is probably what you need. The receiver can be a pocket radio

Or if you're close to the camera, then the remote signal can be either: a) audio tone, or b) light beam.

This light needs to be completely autonomous, it will simply be turned on at deployment via the switch below which will turn the light on by connecting the circuit while completely enclosed within its waterproof housing ( 5A / 120V ) my question is more concerned with the conversion from a large lithium battery bank into a single LED which can remain on for up to 24 hours before it requires a charge. Unfortunately I can't turn the led on once per minute (which is my current setup to conserve battery), I need a consistent light source to allow any and all movement to be captured.

This is not a complex circuit by any means, essentially just a giant flashlight battery on a very small LED. If anyone has any idea as to an appropriate battery size and resistors necessary to step down the voltage that would be great.

Thanks for the input.

 

[dick_freebird]

You could of course chop the illuminator at other
duty cycle and rep rate to match the "activity window"
you expect. For example 10ms on time and 1 sec rep
rate might catch passers-by where 1 sec on, 1
min cycle might miss. Need a little bit of work on
the detector perhaps, to deal with the chopping.

A reed switch and coil can make a neat, waterproof
"divorced relay" that crosses a pressure vessel.

 

[crutschow]

200mA @ 24 hours requires 0.2 x 24 = 4.8Ah, so you need a 6V battery with about a 6Ah capacity (for margin).
If you need to step down the voltage for the LED, then use a constant-current buck regulator for maximum efficiency.

 

[Jesse the Biologist]

200mA @ 24 hours requires 0.2 x 24 = 4.8Ah, so you need a 6V battery with about a 6Ah capacity (for margin).
If you need to step down the voltage for the LED, then use a constant-current buck regulator for maximum efficiency.

That was super helpful, so I'd like to increase the current to run an effectively brighter LED, I've been looking at the 1.9 volt 1 Amp 850 nm LED. What would you recommend to run a light like that for ~24 + hours? Thanks

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