Modding car headlight LED Bar lights for video?

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dv416

Well-known member
There are a lot of reaally powerful LED's out there already built out and ready to go, but they're for cars - headlight alternatives, for offroading and such.

Here's the most powerful one I've found, 300w, and allegedly outputs 30,000 Lumens... for $158

http://amzn.com/B00F4MQJ5O

Now, there are many others too. Perhaps more reasonable for my needs, such as this one... 120w, 7500 lumens, $68

http://amzn.com/B00C0SQ8KG

Regardless of the specific model, or style, has anyone taken one of these rigs and modded it for video use specifically? IE - giving it an AC power source and rigging it to a dimmer. That is possible right? My main use for this would be to use as a ceiling bounce light, to cleanly raise the overall ambience in my studio, without adding much heat or drawing much power. My non-DIY alternatives, even the cheapest out there, are the chinese 1x1 litepanels-style lights which are about $200+ each, 36w / 3300 lumens.

What are some things I should consider if attempting this kind of mod? Thanks!
 
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While powering it from AC would be fairly simple, you CAN NOT dim LEDs the same way you dim conventional lights. The electronics in the fixture can be severely damaged if you do this.
 
Rather than dimming, which might require a different constant current driver, and thus more money, you might consider adding switches in line to some of the LED's so you could turn them off. However, depending on how the unit is wired, that may not work (i.e. if all the LED's are driven in series, or some such). Watch out that you don't over drive the remaining LED's, in case turning some off forces additional current into the one's still on.

Color cast might also be an issue. Still it might be worth a try. Anything that makes light is fair game, as long as it does what you want it to.

I might try and test this unit:

http://www.amazon.com/dp/B00K6Z78N6?psc=1

Lots of new things to try. Thanks for posting.
 
What exactly is it that makes the dimming so universally standard in LED video lights then? Is it because they get a constant current from batteries?

Also, I have seen other LED devices out there that also use an array of Cree 3w lights, which DO claim to have dimming. For example this light, designed for aquariums.

http://www.lightexports.com/servlet/the-8528/led-aquarium,-reef-led/Detail

Does that mean ALL cree lights have this ability? Or is it the electronics in this aquarium light specifically that make dimming possible?
 
dv416 said:
Does that mean ALL cree lights have this ability? Or is it the electronics in this aquarium light specifically that make dimming possible?
Click to expand...

It's the circuitry that drives the LEDs that dictates whether or not it can be dimmed. Since you want to drive a 12 volt light from 120 AC, you will need a power supply. If you dim the AC with a household dimmer, you will damage the power supply. Depending on what's inside the fixture itself, dimming the 12 volt power may or may not damage the circuit.

The aquarium light you linked to is designed to run on AC power, and has circuitry that will work with a household TRIAC dimmer.
 
Are there power supplies that not only transform 120v to 12v but have a dimmer built in?

In other words, what is an AC pluggable LED with dimming circuitry (such as this one: http://amzn.com/B00686PZYG) doing with the 120v electricity coming in that makes it work correctly, and with dimming?
 
It's called PWM (pulse width modulation.) It essentially turns the power on and off really fast, so fast our eyes can't see it. The frequency (width) of the pulses determines the brightness of the LEDs. This happens on the DC side of the circuit, after the 120 VAC has been converted to 24 or 12 VDC.

Household dimming does a similar but not quite the same thing to the AC wave, by chopping up the wave into pieces, and throwing some of it away as heat. The chopping up of the wave has some side-effects, namely tungsten filaments will hum or buzz. That's fine for a light bulb, but potentially devastating for the chips and components in an LED fixture or 12 volt DC power supply.

A much cheaper way to achieve what you want to do is just to get a cheap LED fixture and put ND on it. You won't be able to dim it, but you will still have control over the intensity of the light.
 
Thanks thats a great help. Explains the dimming / flickering phenomenon in LED's too.

Would any 120v to 12 or 24v transformer / power supply work for my purposes? And on that note, would 24v have less chance of flickering than 12v? looks like this particular 300w bar light can handle anything from 10-30v
 
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There won't be a flicker unless you use a PWM dimmer with a frequency that's too slow.

You need to check the current draw of the light. I like to add in a safety buffer, too. So if the bar draws 10A @ 12 V, I would get a 15A power supply. Voltage and current are inversely related, so a higher voltage PSU will need less amperage to drive your fixture.

Now Watts is related, too (and Ohms, but we don't need to deal with him.) W=VA. Since your fixture can handle 10-30 volts, we can do some maths.
Code: 
300 = 10 * A
A = 300/10
A = 30

Now let's do it for 30 volts.

Code: 
300 = 30 * A
A = 300/30
A = 10

And now for 24, since that's a very common voltage.

Code: 
300 = 24 * A
A = 300/24
A = 12.5

So you need a 10 volt 30 amp power supply, a 30 volt 10 amp supply, or a 24 volt 12.5 amp supply. Using the same formula (W=VA) you can figure it out for any voltage, AC or DC as long as you know at least two of the variables.
 
Thanks for that, again very helpful.

Would something like this work? http://amzn.com/B005CLDOW8

Also, does a certain voltage or current mean less heat is given off, or is heat related more to power draw? The point being, to get the quietest fan / power supply possible.

Finally, the 300w power draw... there is no reason that number would fulctuate would it? The lights determine how much power is drawn, NOT the power supply determining how much power to send... correct?
 
Take a look at Meanwell Power Supplies. The efficiency of the PSU dictates how much power is lost as heat. There are power supplies that have built-in fan controls based on the temperature of the components. Meanwell also have convection cooled PSUs.

The power draw is dictated by the thing that is consuming the power. If your PSU is under-powered, either the lights wouldn't turn on, the PSU would shut off, or the lights would run at a reduced output. If the PSU is over-powered, nothing bad will happen.
 
Has anyone bought the Eyourlife 300W 30000LM Led Off Road Light Bar Flood Spot Combo Beam yet?
I am very interested in in this unit. Do you think it would be good to hang above a green screen or maybe a little more in front to help light up your subject. For the price of 100.00, it sounds like it would be nice to try out.

I bought a LED light at Menards that cost about 150.00. I use this all the time as a back light and other uses.
If you are interested in seeing a picture of it, it is on this video.
https://www.youtube.com/watch?v=P72dH6PQjDs&list=UUGV4hvTAboP6eRixCPSPa7w
 
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