Feasibility/Cost: Video Lighting Project

Hello everyone,

To start with, I should mention that I am relatively new to Arduino and have really only played with the basics. However, it occurred to me the other day while I was shopping for video lights for underwater applications that this might be something that - with a lot of effort and time - I might actually be able to build myself.

My project would involve developing a controller for a number of high power LEDs (white). From initial research, I understand that I will need to use transistors and an external power source for running the LEDs since the Arduino board cannot handle that much current.

I have not worked with high power LEDs and do no know anything about the implications of heat buildup that would be due to nesting them close together in the form of a lighting head.

All of this will need to be fitted into a housing capable of about 90 meters depth - here I may have an in a be able to get it machined at cost. The housing will need to have switches to control the LEDs (on/off, and it would be nice to have variable light output as well).

That much seems to be doable to me. I don't know much about batteries, however, and what would be available to run this setup. My constraints are mainly size - I don't want to try to put a lead-acid battery inside of an underwater housing. Smaller is better. Run-time at maximum power would be ideally 45 minutes or more and maximum light output would need to be somewhere around 3500lm or greater.

I guess I'm just looking for any input that you might have for me. I'm willing to spend some money on this project considering the alternative is buying video lighting systems which seem ridiculously expensive to me. (e.g. - this 4000lm video light for $1600: http://www.scuba.com/scuba-gear-56/026844/Light---Motion-Sola-4000-L.E.D.-Video-Dive-Light.html?gclid=CIz7-9mbqLMCFYN_QgodrToAPw )

Any suggestions of where to look to get started, or advice on whether or not this endeavor is even with worth my time would be very helpful.

Thanks!

I don't really see where the arduino fits into this project.

To drive high power LEDs you need a constant current drive and you need one for each LED or group of LEDs in series. You should not connect them up directly to a battery or even through a resistor, the current needs limiting properly.

As for batteries look at the small lithium batteries used in RC models and robots. They are small light and have a very high current capacity.

Thanks for the reply. I did come across constant current drives in my initial research. I had assumed that I might still need an arduino to control the dimming of the LEDs, however... would it be possible to do that without an arduino at all?

No, you don't need an Arduino to dim the LEDs, any source of PWM will do.

This seems an awful lot of bother to go to - isn't there anything in the Greenforce range that would do the job?

Keeping out a 90 metre head of water is pretty tricky too.

If you get the right sort of constant current driver you can simply use a pot and control the amount of current, that will act as a brightness control. However some simple constant current drivers use a small resistor in series with the load to control the current and it is not feasible to make that into a pot. Look for the type of constant current circuit that has an op amp in it.

It doesn't seem like an Arduino project to me, although there's plenty of information here about how to drive LEDs that you may find useful. The hard part as I see it is making the whole device waterproof to that sort of depth, given that it needs a translucent part and some controls, and presumably electrical access to the batteries for charging. Do you have any experience of making waterproof enclosures? If not, I suggest you need to solve that problem first. Sorting out the batteries and LEDs would be quite straight forward in comparison.

Wow. Thanks for all the help and suggestions, guys. It's obvious that there is quite a bit of combined experience here.

As for you suggestions - I'm not sure that greenforce (or any other technical light manufacturer) has anything that will work for my application. It seems like they should, but all of their lights are very focus beams. I'm looking for a very wide spread as I do mostly wide-angle video.

In terms of the waterproof housing - no, I have never built one. I am quite familiar with them, however. I use waterproof lights, camera housings, and dive computers, and do the maintenance on all of these myself. In this case, I think the housing would be rather simple and I would probably use magnetic switches to avoid any extra failure points. But that's probably a discussion for a different forum! :)

Anyway - it's something that I think I might want to play with for the fun of it and I thank you all for pointing me in the right direction. Much appreciated!

As the subject heading says 'Video Lighting Project' you may need to be careful using PWM to dim/drive the LED lighting as you could end up with a varying strobe effect as the LED's are dimmed.