Improving illumination


#1

Hi
I am having problems with visibility in dark lakes here in Ireland. Its really black and dark and the lights on the ROV seem to get lost in the darkness. So basically I need more lights. Any suggestions on how to modify the ROV or to create an add on module with more lights.There will be an obvious extra drain on the batteries and wonder if I would need to rescale everything to see in the dark?


#2

I guess you just need to look at adding some LED lights, based upon their power requirements. It’s a fairly simple calculation–power (watts) is voltage X amps. Your batteries will have a rating of amp-hours, which should really be converted to watt-hours. But you can simply have to do the math I’d think, in terms of whichever LED lights you go with. Once you have one or two extra lights added and can get a feel for how much power they require, then you can make a decision as to how many more you might need to add.

As for the location of mounting them, I won’t be able to help you much there I’m afraid. I haven’t even put my kit together yet as I’ve had too much stuff to do since it arrived. But I should be assembling it within the next month or so…just in time for the winter in Wisconsin!

(No, my timing isn’t all that good.)

TB


#3

Is part of the problem that the water is murky? Are there floating particulates in the water? Does stuff in the water close to the camera get lit real bright and cause the camera to dim the whole scene so what you want to look at it too dim? If so then just adding more light may not be the answer. You may need to improve the geometry.

The ideal geometry for murky water is an equilateral triangle between the lights, the camera, and the subject you want to look at. That is often impossible but the more distance you can put between the camera and the lights the better. You specifically want to avoid illuminating the murky water between the camera and the subject, so making the light directional so it shines on the subject but does not shine close to the camera is good even if it takes making a tin shade to put the area in front of the camera in shadow.

SherpaDoug


#4

Hi
TB: Thanks for the advice, may have to source more LED’s and rework the board .

Doug:
Water isn’t murky, just dark. What you posted makes sense though and I will experiment a bit. Will be trying a wireless controller in a couple of weeks and will get a better sense of the problem. On a sunny day the sunlight lights up the water but the dark days which I prefer as its easier to see the laptop screen the darkness of the depths predominates. Thanks for the help.


#5

You will need lights with narrow beam…the narrower the longer throw…as I am diving in the north of Norway I know this :slight_smile:

The internat light of the rov is ok for closeups…but for forward looking … how about mount some dive light on the outside?. . E.g one on each side?
Guess they will brun for an hour or more… depending on the band or type


#6

Hi Tom
Thanks for the suggestion, a very good idea. I will look online to see what’s available.

Cold diving up there in Norway especially in winter and dark too. Here our summer was dark and cold.
Regards,James


#7

I guess the thing is that once you’re deeper than the light from above can penetrate, you are at the mercy of power vs. light output. Also, the inverse square law probably applies in water as much as it does in air, i.e. the illumination falls off as the square of the distance, twice as far, 4 times less light.
Andrew


#8

Thanks Andrew
You are correct regarding the inverse square law applying in water as well as air and I will have to experiment to improve the output.
James


#9

If you get an option, maybe RGB LEDs with vary narrow emission angle. That way, you could get more penetration with green light when you want it, white when you need it, and red to add back red light for pictures (due to lack of penetration of red light at depth). Another thought, if you DO happen upon murky water: polarized filters in front of LEDs and one in front of camera lens. If polarized filter could be rotated by encoded motor, difference between two sets of polarizers could reduce (but not eliminate) particulate light scatter. Also polarizing lens filter and LED filters could open the possibility of stress inspection (maybe) in the case of polycarbonates and polystyrenes (stress induced birefringence). Sorry- rambling, but ALSO depending on what RGB LEDs you choose, fluorescence could be observed when color of LED brought up to near ultraviolet.


OpenRov 2.8 auxiliary wires specs, adding external lights
#10

Hi James:

Here at OpenROV we are slowly moving towards selling external lights for the ROV. Over the past year and a half we’ve been through about a dozen different configurations for external lights, including trying to decide whether to offer do-it-yourself kits or having them totally pre-assembled.

At this point we have a design for a generic pre-assembled external light done, and the prototypes all work well. It needs to have the finishing touches put on it for production, and that effort got put on the back burner as we got OROV 2.8 into production and the prototypes for Trident working. We’ve only got so many folks around here, so we have to carefully pick and choose what we’re going to work on.

One of the things we did on 2.8 was to make it pre-wired for external lights; if you have one of these ROVs, all you’ll need to do is hook it to the correct spare wires in the wire harness and it will work. For earlier 2.5/2.6/2.7 ROVs, there will be some wiring required internal to the vehicle.

Now that 2.8 is out the door, and the Kickstarter for Trident is launched, we’ll have a little bit of time to work on accessories. The external lights are one of the things that will probably get some time in the upcoming months.

-Walt


#11

I used Beam lights and they worked well. They are, I think, backup lights for cars.

http://www.dx.com/s/led?category=1350

so me examples there.