100W LED Driver options?

[Starflexx]

I'm looking into possibilities for building cheap high power video lights using a 100W LED SMD array and running two light heads, with one 100W array in each, from a 12V Ni-Cd or Li-Ion battery pack.

LED SMD's I've looked at are something like these:
http://www.ebay.com/itm/New100W-LED...ing_Parts_and_Accessories&hash=item3ce4ab92e1
or
http://www.ebay.com/itm/CREE-XLamp-...458?pt=LH_DefaultDomain_0&hash=item1c4312bbb2

As for drivers, the only two I've found which I think could work that does step-up from 12V and handles 100W are variants of these:
http://www.ebay.com/itm/DC-DC-100W-..._Measurement_Equipment_ET&hash=item3ce49e9fd2
or
http://www.ebay.com/itm/100W-DC-DC-...Driver-Constant-Current-Voltage-/271455842760

I would like to be able to dim the lights as well. Either in 3 or 5 preset steps like 20, 35, 60, 75 and 100% or adjustable 0-100%. I prefer the on/off and dim-button to be the same for both heads so that one button adjusts both light-heads. On/off and dimmer could be two different switches/buttons though.

Also looking into fitting low voltage warning/protection and high temp protection.

I am familiar with electronics, but not so much designing components or circuits out of needs, and I haven't found what I'm looking for online just yet.

Anyone with knowledge on LED drivers that could help?

 

[DIWdiver]

Those regulators look like they should work. I've been interested to see what they will do. Let us know if you try it.

When pushing them up around 100W, the efficiency may drop quite a bit. You may also have trouble getting max power out of them with a large step-up ratio. I would advise keeping the battery voltage as high as possible, like maybe 24V, unless you get the regs and test them, and see that they are okay boosting 12V to 35V.

The only way I can see to add analog dimming control to them is to build a board with a microprocessor, connection for the pushbutton, and two digital potentiometers. Then pull the current adjust pots off the regulators and wire the empty holes to the pots on your board. It's very doable for someone skilled in the arts, but for a beginner there would be a lot to learn.

Or you could (maybe) use a PWM dimmer. Since these would be video lights, you'd want to be careful to make sure you use a high enough frequency to prevent artifacts in the video image. I've seen one product site that claims theirs runs at 2000 Hz, and that is enough for video, but I doubt that. I would do some research on CPF and elsewhere to determine the minimum frequency you need.

The advantage of PWM dimming is that you could do it without modding the driver. You essentially use a high speed electronic switch to connect and disconnect the LED from the output of the driver. The relative durations of the on time and the off time determines the apparent output (but in reality you have full on and full off - which the video camera can see much better than you can). Unfortunately, not all drivers will behave well with this kind of load, especially at high frequency.

Another option is the HBflex board from Taskled. You'd need one for each LED, and I'm fairly sure we could figure out how to run them off one switch, even if we had to help you build a little (very simple) board to do it.

 

[mikews]

@DIWdiver
Iam not very good on electronics but can this dimmer work for this kind of application ? Iam building a dive light very similar with this one but with out any switches,sockets for charging etc to keep any leaking chances to zero and i liked this one for the dimming options.Just need a waterproof case for the remote.
By the way thank you for the technical knowledge you share on this forum.Helped me a lot.

 

[DIWdiver]

Assuming you find a regulator that will work okay with a PWM dimmer, that one looks like it should work, except I would guess the frequency is too low for video. No guarantees though.

 

[joachimk]

https://www.youtube.com/watch?v=BKyaFGOZtaM

this is a test we did with a pwm generator
the first one you see is at 2Khz the second one is at 500 hz

So you see you need to go higher than 2Khz to get the banding out

 

[DIWdiver]

Excellent!

That shows us that various combinations that seem pretty similar can result in dramatic differences in results.

Even at PWM frequencies of several thousand Hertz, the camera settings have a substantial impact on the results. You may be able to take great video with 500 Hz PWM and certain camera settings, or you can get disappointing results at 2000 Hz.

Since some drivers have PWM frequencies that change over operating conditions, you'd want to make sure you get one with fixed frequency, and test, test, test, before going out to shoot good video.

 

[Starflexx]

The frequency of a PWM could have significant effect on video, I might look into that a bit more. Thank you for the replies so far.