Build the MOAL -- Mother of All Lights, or at least a really good set of video lights...
For the TL;DR crowd: This project is a Video Light that is light, bright, and can easily be built using a half size baking sheet, twelve 10W LED's from eBay and some simple electronics. They perform on par with lights costing 5-10 times as much. Light output is 2300Lux at 1M over a wide area and they have really good CRI. Three lights and associated power supply can be built for about $250 to $300.
As I learn more about filmmaking, videography and photography, the more important lighting becomes. To look professional, you must light professional. That doesn't mean that you have to spend a fortune on studio lighting. Especially when you can build some pretty functional lights yourself. My goal was to build a basic set of three soft or diffused lights. This lets you do the classic “three point lighting” setup and most standard lighting setups. I am a huge fan of LED's and naturally, went for those. The design challenge for me was to accomplish three things:
First and foremost I wanted a lot of light. Could I do this with LED strips? Not sure. Second, I didn't want fans on the light heads so that there wasn't noise produced near the camera. This meant I had some thermal considerations in removing heat from the light heads. Third, I wanted them to be dimmable. After several missteps and design changes, this is what I came up with: MOAL, the Mother of All Lights. Using these will give a 1000 Lux into your scene easily.
Background for lighting:
Studio lighting comes in a several forms. There are Fresnel lights which are named for the lens that is used to focus them. They give a very focused light that can be later diffused by shining on a reflector or other surface. Then there is a company called Kino Flo that makes rectangular larger light sources, either using fluorescent tubes or arrays of LED's They are so well known in the industry that their brand name has become the name for that style of light. Then finally there are arrays of LED's that are similar to the prototype I made with just covering a baking pan with LED strips. Some of these are good, some are not.
The first property of a light is the amount of light output. This used to be quoted in watts which correlated more with the power consumption of an incandescent lightbulb. A more accurate measure is Lumens or Lux. LED's are much more efficient than halogen or even fluorescent lights. So to compare them requires converting power to actual light output. The LED's we are using in this project are rated at 10W power consumption and put out about 800 lumens at that rating. We are derating slightly to 8W to keep the heat down. Each light has 12 of them so each light puts out just under 9,000 lumens. This is on par with a 500W Halogen light. Not to shabby! Especially when you use three at once. There is far less heat produced so your set or what ever you are lighting will stay cooler.
Background on the design:
I had my Ah Ha! moment when shopping at a local restaurant supply company Acemart. I stumbled across their aluminum baking sheets. They were six bucks each, and on sale for four in the front of the store. Aluminum which has great thermal properties, is also easy to work with. So I bought a few of them. My initial thought was to cover the bottom in LED strips, so I ordered a couple 5M rolls of warm white/cool white strips. I figured with those I could make the light color temperature adjustable. That worked but had two shortcomings. First, it was a complete pain in the butt to cut the strips, then make and attach all the jumper wires to connect everything. Honestly I spent all afternoon doing that. Second, while bright, it didn't put out as much light as I had hoped for. I had about 800 Lux at one meter. The final configuration has about 2300 Lux at one meter. I liked having the warm white and cool white LED's both on at the same time. With the ability to completely color correct in post, I decided against making the final build color temperature adjustable (Although I will show you how if you so choose) If you are into video editing I highly recommend you check out DaVinci Resolve. It is free and quite awesome. With that program, you can easily adjust color temperature after filming. I filmed using these lights with my camera set to fluorescent. I did no color correction in the included video. I filmed the entire video with my Canon 7D using a couple different lenses and my GoPro.
My final design has 6 warm white and 6 cool white LED's giving you about a 5000K color temperature. It is a mix of 3500K warm and 6500K cool. These 10W emitters are actually made up of 9 LED's internally wired 3 in series and then the 3 strings in parallel. White LED's are actually blue LED's with a phosphor coating that absorbs the blue light end emits the rest of the light spectrum. My choice of two different LED colors should improve overall all CRI or color rendering index. Read more on that here. And specifics of LED thermal management here.
And now for the math. Each actual LED has somewhere between 3.2 and 3.4VDC forward voltage drop across it. This depends on the die temperature and current flow through the LED. We are not going to worry about that part. For ease of the math, each 10W LED has about 10VDC across it at nominal current. Each 1W LED die has a nominal current of 330Ma. So for the whole 10W LED, we are looking at 1 amp of current with about 10 volts dropped across it. If we put three of these in series we have 30VDC. Now if we parallel two of those strings, we have two amps of current. I gotta throw this out here: There is a YouTube video of someone dissing the “Cheap” Chinese 100W LED plates. He shows how each LED lights up individually. He puts very little current into the LED array and catches them lighting up one at a time. Then of course, blames the manufacturing process. You can easily repeat this by slowly raising the voltage to the LED assembly. The LED's start producing light about 2.3 volts. At first one lights up and then a few more until they are all lit. His implication is that they should all light immediately. There is a huge difference between a few milliamps of current and full rated current. See the video in instructable for this in action. China pioneered the plate multi chip LED. Eighty percent of their outdoor and commercial lighting is LED. I have spent time in Shanghai and Shenzhen over the past decade and have watched all of this evolve. They may have some quality issues here and there... Any one for a Hover Board? I saw this with my LED strips. My warm white/cool white strips actually used the flexible PCB strip from an RGB strip and are labeled RBG and +. It only used three of the four connections and I had to sort out how to connect it.
For the actual design, we are using twelve 10W emitters, six cold white and six warm white. This gives us a power requirement of 30 Volts at 4 amps. To provide dimming we are using a 555 based variable PWM circuit that runs at 27Khz. This keeps it from causing any issues with flickering at normal video frame rates. This is about this simplest way to do this. For current limiting and control of the LED's we are using the same MOSFET circuit I used in my Larson Scanner instructable. For the Rsense resistor I selected .33Ohms which gives us about 1.7 amps of current. I am using two of these, one drives the cold white LED's, the other the warm white ones. This enables you to easily make this color temperature adjustable by adding an additional PWM circuit. To make this a functional light, we need structural integrity and the ability to mount it to a light stand. I added a two metal braces I got from Lowes to the baking sheet using a 1/4-20 bolt and a mount for the light stand from Amazon, this one.
To power the lights, I put two 30 volt universal switching power supplies into a industrial case that I also got at Lowes. Each supply can supply two lights. These get adjusted to 34VDC to give the Current Regulator four volts of headroom to work with. As I adjusted this with my prototype, I found that the LED's visibly went up in brightness as I adjusted voltage up, the brightness didn't go up past 34 volts. My supply did adjust all the way to 37 volts. I settled on 34 volts for the operating voltage. With a 4 volt drop across the MOSFET, they dissipate about 8 watts of power, which keeps their temperature rise on par with the LED's. I let my prototype run for a several hours while checking the temperature of the all the components and the baking sheet overall. Nothing got above 45 degrees C. Hot to the touch, but well within the operating temperature of all the electronics.
To connect the light to the power supply I used 18 gauge SOOJ wire, which means “Service and Oil resistant inside and Outside Wire.” Type SOOW Cable is for use in heavy-duty industrial applications where flexibility and durability is required. It is 23 cents a foot mail order. I used Speakon connectors at the power supply and directly connected the lights, bringing the wire in on a strain relief mounted on the back of the baking pan. I used 25ft of wire on each light. This makes the whole setup very robust, durable and professional.
To complete this you will need light stands. I already had two light stands but I got another one to round out my collection to three. Cowboystudio is a great source for these. I bought this one there. If you live in the DFW area of Texas, you can go to their showroom.
Taking these to the next step I am going to add some diffusion directly on the baking sheet. I ordered some cloth used for soft boxes to experiment with. I am also looking at how to add some barn doors to control the light spread. For filming I used gaffers tape and black foam core board to control the light pattern. The power supply and circuitry lend themselves to powering 100W LED's which have a10X10 LED matrix internally. More to come as I look into more video lighting possibilities. I will update the Instructable when I sort out the diffusion and barn doors.
All the steps for construction are in the Video. I hope you enjoy!
Step 1: The Schematics, Parts List and Wiring Diagrams
In one sense, this is the shortest Instructable that I have done. Two Steps. With the video I put together, it is probably the longest one that I did. Here are the schematics, Parts list in an Excel sheet and the wiring diagrams you will need to build the MOAL. I also included the DATA sheets for the MOSFET I am using and the 12 volt regulator. All lighting for my video was done with these lights. If you have any questions, please reach out in the comments. I am including a "Selfie" taken with the lights and my Canon 7D using a Sigma 18-35 Lens and no touch up in Lightroom. This is without the umbrella diffusers and you can see each LED in my glasses.