Ring light 2.0: 90 LED ring light

There's something magical about ringlights. The unnatural light cast, the halo shadows. Yet the idea behind it is as clever as it is simple: looking through the light source.

Overview

Want to see more ring lights? See my full ring light overview page

Quick overview:

4.1

 Fiber optic TTL flash ring light, uses popup flash and 67 fiberglass bundles

4.0

 Fiber optic TTL flash ring light, uses popup flash and 120 plastic fibers

3.1

 2 CCFL continuous ring light

3.0

 4 CCFL continuous ring light

2.1

 52 mm filter mount 140 LED continuous ring light

2.0

 52 mm filter mount 90 LED continuous ring light

1.0

 Simple, 30 LED continuous ring light

Just a few months after I built the 1st LED ring, I started getting filters and achromatic close-up lenses and all that kind of stuff. The ring had become too small to fit around the 52mm filter size I was using. Apart from that, the mount was very clumsy, not something you want to use for serious shots. Thus arose the need for a larger and better ring that would fit on a standard filter mount.

Click thumbnails to zoom in. Click again to zoom out, or use cursor keys to walk through all images.

1. I trashed the old one (no point in keeping it, except for that flashlight, which is lame) and started cutting rings again.
1  
1. I trashed the old one (no point in keeping it, except for that flashlight, which is lame) and started cutting rings again.
2. And again, started soldering led strings of 10.
2  
2. And again, started soldering led strings of 10.
3. And again, put those led strings between concentric plastic rings.
3  
3. And again, put those led strings between concentric plastic rings.
4. But this time, I decided to use as many of the white leds I had in my supply box, and started adding a <i>second</i> ring of leds.
4  
4. But this time, I decided to use as many of the white leds I had in my supply box, and started adding a second ring of leds.
5. A view of the back.
5  
5. A view of the back.

The inner ring is already larger than the old ring in itself, and consists of 42 leds. The outer ring has room for 48 more leds. That's a total of 90 white leds, adding up to 8 electrical Watts of light, all thrown in one direction. The power supply has lots of current to spare, so tripling the amount of leds won't require any changes on that department. For info on the power supply, see also Ring light 1.0.

6. This is the first test drive, with the glue for the outer ring still setting, and the power supply housing in place
6  
6. This is the first test drive, with the glue for the outer ring still setting, and the power supply housing in place
7. I ended up using 4 plastic rings from 2 different tubes to hold the 2 led rings, and 3 smaller rings to get to the outside diameter of a 52mm filter rim. Everything was glued together and here's the result. You can see the camera adapter tube screwed onto the filter rim.
7  
7. I ended up using 4 plastic rings from 2 different tubes to hold the 2 led rings, and 3 smaller rings to get to the outside diameter of a 52mm filter rim. Everything was glued together and here's the result. You can see the camera adapter tube screwed onto the filter rim.
8. The first test fit on the camera. Don't mind the extremely low quality picture; this is how a Fujifilm DX-10 performs in less than perfect lighting.
8  
8. The first test fit on the camera. Don't mind the extremely low quality picture; this is how a Fujifilm DX-10 performs in less than perfect lighting.

A problem arose with the power supply after all. It draws excessive current when supplied with enough juice at 5 volts, and by the looks of it, it seems the energy storage coil is saturating. I don't have any details on the coil itself, except that it came from a step down converter, it's 470 uH, and it worked well with 30 leds. I have to verify this at work, where I have abundant measuring equipment. A quick test revealed that it would work fine and efficient from 7.2 volts and up, so powering from a 4 AA pack is out of the question, until I resolve this. I guess I will be using a 6 or 8 AA pack. I improved the inrush current by inserting a capacitively coupled diode clamp to the Vc pin. This way, a weaker power supply will be able to start the converter more easily.

Update: later tests revealed the culprit was actually the batteries. On a high quality set of 4 NiMH AAs the converter starts up just fine.

Results

Now for some LED ring light results:

9. B03404 Tube lamp
9  
9. B03404 Tube lamp
10. B03745 Tetrahedron
10  
10. B03745 Tetrahedron
11. B03707 House spider
11  
11. B03707 House spider

The spec sheet:

Specifications
Dimensions Outer diameter
Depth
Converter part


Mount		 93 mm
40 mm
protruding 16 mm outside diameter
and 45 mm towards camera,
including angled power connector
52 x 0.75 filter thread
Electrical Input voltage
Input current
Converter output
Converter efficiency
Power connector
 7.2-25 V, 15 V nominal
600 mA at 15 V
32 V, 240 mA
85% at 15 V input
DC plug 5.5 x 2.1 mm
Optical Color temperature
Light output
Exposure value		 appx. 9,500 K
appx. 200 Lumens
13.5 on white paper from 35 cm,
corresponds to 1/200 s at f/8 at 100 ISO

And lastly, here is the schematic:

Continue reading about ring lights: Ring light 2.1



© Joris van den Heuvel, Fuzzcraft.com