LED light panel

[macandal]

So I'm sure some of you have already seen this. I thought it was pretty cool how this guy made an LED panel and he made it look simple to make. Of course, for those of us who are totally bad at manual things, this seemingly "easy" project would be quite a challenge. Have any of you made one of these? Any advice on how to proceed? Perhaps someone has an even easier way to make one of these--I'd love to hear it. Someone wants to get together and build one? I'm in the San Francisco Bay Area.


https://youtu.be/jLia59KfkSw

[vinny]

This may help a bit: http://www.litegear.com/
We've been using this stuff for several years and it's become a staple for tv and film production.

[macandal]

This may help a bit: http://www.litegear.com/
We've been using this stuff for several years and it's become a staple for tv and film production.Nice, but pricey. This DIY option is good because what would cost you $2000 in litegear.com you can build for about $100. True, as I said in my post, I can see myself building it up to a point but I'd be stuck after that. Anyway, thanks Vinny.

[vinny]

Yeah, that link was more for design ideas. Litegear isn't cheap but that's not an issue in the motion picture industry:)

[jp]

You can get LED panels advertised as grow lights, as well as LED panels meant to replace ceiling tiles shaped fluorescent light fixtures. Both would need a tripod screw added but are otherwise pretty close to ready. Color quality won't be as nice as a fancy big budget light, but for B&W film it won't matter.

[Jon Shiu]

A pretty cool DIY project with dimming and lightweight portable battery. I want to make one. Good winter project maybe.

If you do make it, study up on the RC LIPO batteries because they can if damaged or over-charged/discharged burn down your house. Or perhaps just use a corded power supply at first.

Jon

[macandal]

If you do make it, study up on the RC LIPO batteries because they can if damaged or over-charged/discharged burn down your house. Or perhaps just use a corded power supply at first.

JonJon, if I did make mine, I would not use that battery. I would attach a cord to connect to an outlet. Too bad he didn't go over that step. I wouldn't know how to do it.

[A_Tabor]

I would really encourage people to stop and study electronic design and fabrication theory and methods before taking off with a project like that. Also think about how and where you are using them, and the related liability that comes with them. They're not a certified and approved device, and in the event of an accident the insurance agency is very likely to look at the remains, ask the make and model, and then smile and nod while closing their cheque book and walking away from you.


They are neat things that you can build with only a little investment, but waving away and ignoring risks involved is a good way to start fires or give someone a nasty shock.


Also consider general quality control and reliability. Really cheap LEDs that you can get a 'great deal on' from Ebay and such can be prone to high failure rates and wide specifications. I've seen more than a few people build similar panels and end up with uneven lighting across the field, which in turn ended up with dead LED cells bringing down the entire panel. Plus some suppliers tend to be a little liberal with their data sheets and specified outputs, so read up on a given supplier before buying, and be wary of deals that look too good to be true.

Building a very reliable, consistent, and robust product is not an easy or cheap task.

My best advice is to slow down, and don't rush a project like this. Take the time to understand how things work and why they get designed the way they do, and don't blindly follow really simple instructions off the web.

[Jon Shiu]

Jon, if I did make mine, I would not use that battery. I would attach a cord to connect to an outlet. Too bad he didn't go over that step. I wouldn't know how to do it.

The reason he used the yellow XT60 connector is so he could switch out the battery and switch in a laptop power supply. Instead of the XT60, you can get a socket at Radio Shack to match your laptop power supply, or just cut it and hardwire it if it's an extra power supply.

Jon

[Peter De Smidt]

People make aquarium fixtures much like these all the time. Is this for color or bw?

[macandal]

People make aquarium fixtures much like these all the time. Is this for color or bw?Mostly B&W, but I'm not ruling out color.

[Peter De Smidt]

For BW it shouldn't be easy. For high quality color, well, that's another story. For color, you generally want 5000-5500K and a high CRI (Color Rendering Index). That's not all there's to it, as there's ways to fudge CRI, and it only accounts for a small number of colors. Cree and Nichia make fairly high CRI leds. Check out some sites such as: https://reefledlights.com/how-to-diy-led/ . Note that you'd use different LEDs than the aquarium people, who often want a lot of blue and uv.

[Eric Biggerstaff]

I used this video to create the LED UV panel for my UV box. There is another thread on that project in the forum.

[Jody_S]

Before anyone goes ahead and builds this, you should know the current generation of 2x4' (ceiling tile, 'troffer') LED fixtures wholesale at @ $55 - 60. They go as high as 5,000K, and CRI is decent. I have an older generation 2x2' upstairs, I'm waiting for my wife to score another sample before I try them out as continuous lighting.

Or I could use it to power a DIY 11x14" enlarger head...

[Peter De Smidt]

Building your own won't be cheaper, but you would have complete control over the parts. Cheap panels are, well, cheap. Ime, leds don't last anywhere near what is claimed. For instance, I had a $300 LED light strip, a Reefbrite, with high-bin Cree LEDs noticeably dim over about 2 years. I have a GE LEd bulb in the basement. It stopped working after about 3 months.

We use a cheap LED panel for some interior work. It's generally ok, but it's certainly deficient in the reds. (We use it to paint specific areas.)

[macandal]

Before anyone goes ahead and builds this, you should know the current generation of 2x4' (ceiling tile, 'troffer') LED fixtures wholesale at @ $55 - 60. They go as high as 5,000K, and CRI is decent.Jody, where do you find these? What's the brand?

[Jody_S]

Jody, where do you find these? What's the brand?

Where do I find these? My wife works for the Canadian importer/wholesaler (these are one of her categories, so she's involved in the import, labeling and pricing). They're made in China or Korea, depending on who you buy them from. They're sold under any number of brand names, I couldn't tell you what names are common in the USA. My wife just informs me the $55 ones won't be on the market until October/November. Please remember the electrical distributor will add a 30% or so markup on these, + transportation costs.

I will be able to buy a small number of them at $55, but with shipping costs there is no way it would be economical to send these anywhere. My wife's company does sell some in the USA, you could try these people in the fall: Flynn & Reynolds (http://www.flynn-reynolds.com/)

[Daniel Moore]

Tabor makes some sobering points. In one of my experiments I picked up some chinese 'high CRI' LEDs and upon first powering them up with the properly spec'd power supply several of them began releasing god knows what in the form of stench, smoke and heat. I pulled the plug and tossed them.

Peter D. and I have had much better luck so far with some RGB LEDs purchased from Lee Valley, the Armacost brand, which we use in our DSLR film scanners. They've held out over periodic use for me for more than a year, with no dead elements and no other surprises.

LED flicker has been an issue at higher shutter speeds with their PWM RGB control unit, beyond say 1/30th sec. Not sure what happens at much higher shutter speeds with their controller. I assume using them in a panel such as this is sized, would result in very significant shutter speed increases at normal working distances.

I'll look into the instructions/details for this project further and see what I can learn.

Macandal, I'm in Berkeley. Perhaps we could work together on such a project. Summer isn't a good projecty time of year for me though : ).

[Daniel Moore]

Correction, I did have two dead LEDs in the strip I purchased from Lee Valley. They sent me a 12" long strip to replace them for free and they've been doing fine.

[Pierre 2]

Just on the liability issue : With no batteries involved, not sure that liability could ever be such a big issue : I believe that products operating on low voltage are typically not subject to certification. The power supply, yes as it is a "higher" voltage device. Stick with certified power supply and be sure get one for which the load capacity will exceed the actual load you will be using. A correctly rated fuse on the low voltage side remains a useful feature. Then, what remains are sound wiring (and heat sinking) practices (which may not be everyone's major strength...). Various recommandations obviously remains.


I would really encourage people to stop and study electronic design and fabrication theory and methods before taking off with a project like that. Also think about how and where you are using them, and the related liability that comes with them. They're not a certified and approved device, and in the event of an accident the insurance agency is very likely to look at the remains, ask the make and model, and then smile and nod while closing their cheque book and walking away from you.


They are neat things that you can build with only a little investment, but waving away and ignoring risks involved is a good way to start fires or give someone a nasty shock.


Also consider general quality control and reliability. Really cheap LEDs that you can get a 'great deal on' from Ebay and such can be prone to high failure rates and wide specifications. I've seen more than a few people build similar panels and end up with uneven lighting across the field, which in turn ended up with dead LED cells bringing down the entire panel. Plus some suppliers tend to be a little liberal with their data sheets and specified outputs, so read up on a given supplier before buying, and be wary of deals that look too good to be true.

Building a very reliable, consistent, and robust product is not an easy or cheap task.

My best advice is to slow down, and don't rush a project like this. Take the time to understand how things work and why they get designed the way they do, and don't blindly follow really simple instructions off the web.

[macandal]

Macandal, I'm in Berkeley. Perhaps we could work together on such a project. Summer isn't a good projecty time of year for me though : ).I'm available. Let me know what's good for you.

[jeroldharter]

would be a good light source for lf enlargers.

[macandal]

This just occurred to me. Remember, I'm not a master builder but I was thinking, the guy in the video uses something to make sure that the voltage does not exceed 12V, isn't this what a dimmer does? Regulate the voltage and by regulating the voltage the light gets brighter and darker? Couldn't he just use a dimmer?

(I really hope that wasn't a stupid question. :( :( :( :( )

[chris_4622]

This just occurred to me. Remember, I'm not a master builder but I was thinking, the guy in the video uses something to make sure that the voltage does not exceed 12V, isn't this what a dimmer does? Regulate the voltage and by regulating the voltage the light gets brighter and darker? Couldn't he just use a dimmer?

(I really hope that wasn't a stupid question. :( :( :( :( )
The voltage regulator he used has a trim pot to keep the voltage from going too high when turned full on, a regular dimmer doesn't have this so you would have no way to prevent too much voltage from reaching the light if turned up too far.

[jp]

This just occurred to me. Remember, I'm not a master builder but I was thinking, the guy in the video uses something to make sure that the voltage does not exceed 12V, isn't this what a dimmer does? Regulate the voltage and by regulating the voltage the light gets brighter and darker? Couldn't he just use a dimmer?

(I really hope that wasn't a stupid question. :( :( :( :( )

A dimmer switch is likely more expensive and complicated than a potentiometer (as in the video). They can use different means of modulating power that are undesirable.

The pot has a wiper (middle pin) that moves along an semicircle track of resistor material (outer pins) and is real simple in operation. A 2.2k pot has 2200 ohms resistance between the outer pins connected to the ends of the resistor material. The circuit probably uses this change in resistance to change the duty cycle of pulses going to the LEDs. LEDs don't respond linearly to changes in voltage but you can modulate the energy going to them.

As some LED color is from the LED semiconductor and some from phosphors, I think adjusting the output from LEDs would result in color shifts (phosphor glowing while semiconductor doesn't), which is probably the main complaint of cheap white LED construction.

[barnacle]

LEDs are current devices; they'll drop around 2 to 2.5v across them pretty much irrespective of the voltage. The excess voltage (e.g. a 12v supply driving a single LED with a 2v drop has an excess of 10v) has to be dissipated across a resistor or a semiconductor current limiting device.

The proper ways to drive an LED are twofold: either with an adjustable constant current device (i.e. a device which delivers a preset current in use, which is adjusted for the desired brightness) or by over-driving the LED with a higher current (its specification will indicate a maximum pulse current) and adjusting either the pulse repetition frequency or the on-off ratio.

The second approach has the advantage that it will maintain the same colour temperature irrespective of brightness, but may have issues with strobing on a video shot. The first approach is technically cleaner, and can be more efficient, but it can change colour with brightness.

One advantage in either approach is that you can place the LEDs in series to reduce the excess voltage - for example, eighty LEDs at two volts each would drop 160 volts, but the current would be the same as for one, so a dropper resistance from (say) 200v would be much smaller and be dissipating less power than just trying to drive a single LED from the same supply.

Problems of colorimetry are fascinating: trichromic sensors whether film or semiconductor do not necessarily see light the same way the eye does: a mixed source of light with red, green, and blue components may fool the eye that it is seeing a single wavelength, but it's quite easy to find objects which reflect or absorb particular wavelengths which only appear the 'correct' colour under wideband light, e.g. sunlight or continuous spectrum incandescent lights. LEDs tend to be either single-wavelength (or close to it) for coloured LEDS, or phospors activated by UV for some purple and white LEDs. It might be worth playing with strips of red, blue, green, and white with individual dimmers...

Neil

[Jody_S]

The bottom line is that LEDs simply do not dim. No, a household dimmer will not do the trick.

In order to fake dimming, the LED is simply allowed to cycle off/on and such a frequency that the human eye cannot see the 'off' periods (yes, this allows the phosphorus-based LEDs to go out of balance, throwing off color rendition). More importantly for photographers, the higher the shutter speed, the greater chance you have of capturing some or all of an 'off' cycle. If it's cycling at 20kHz like modern fluorescents, that won't happen. But if it's a cheaper device cycling at 1kHz, it will happen.

If you're planning on using LEDs for photography, I suggest avoiding any sort of dimming. Move the light back a few feet instead, or use a higher shutter speed, NDs, or whatever tricks you have. For enlarging, knock yourself out, but you will notice contrast changes in MG papers as you dim.

[barnacle]

It's not that they don't dim, it's just that the available dimming methods aren't necessarily suitable for a given photographic method.

But hey, I'm a natural light sort of chap :)

Neil