It has been a long time since I try to find the cheap, easy and light way to have a ring light on my camera. Given the big diameter of the high end camera (between 70 an 80mm), most of led rings found for microscopes are too small.

The biggest problem for me is to get a a nice tool, you can pop up out of your bag and stick on your lens like a filter. The printer circuit is the mist difficult thing to find since the whole stuff is nothing else than a big hole with a thin border.

I finally find the solution here

2x 140mm Car Angel Eyes light 42 SMD LED Ring White:eBay Motors (item 260478081380 end time Oct-16-09 09:48:10 PDT) (http://cgi.ebay.com/ebaymotors/2x-140mm-Car-Angel-Eyes-light-42-SMD-LED-Ring-White_W0QQcmdZViewItemQQ_trkparmsZalgoQ3dSIQ26ituQ3dUCIQ252BUAQ252BFICSQ26otnQ3d12Q26poQ3dLVIQ26psQ3 d54QQ_trksidZp3907Q2em263QQcategoryZ33713QQitemZ260478081380)

It is angel eyes ring for car. They are usually cheap (around 10$) , exists in several diameters (form 60mm to 140mm - between 2 and 5 inches ).
The leds found on such devices are not very powerful and not always the right temp. (sometime as high 6000k) but if you are not so bad with your hands you can change the leds.
I think you can purchase several sizes and embed them to get more light. You can even selectively switch the inside and outside ring to control light.

I found a simple and cheap solution that's worth a try on a stills forum.
Buy a bunch of keychain LED torches, they can be had at $3.98 for 10 at Deal Extreme. Put Velcro around lens hood and Velcro dots on each torch. Turn on torches and Velcro to lens hood as needed. I haven't tried this trick as yet. For under $5 plus delivery it's worth a shot though.

received first batch of ring light (with 5050 leds) and very happy.
color and power are really great.

My 'angel eyes' arrived today. Not bad really. Certainly not going to blind anyone with these. LEDs are remarkably free of the green caste. I'm thinking to buy a set of the smaller sized ones as well to get a bit more light.

Giroud,
keep us informed how you go with this project. If you do replace the LEDs I'm interested in how that works out.

I use a Kino flo Kamio.

received the second set of rings with smaller leds.
first set received was same rings but with 5050 Leds
the numbers are the size of led (5050 is 5mm by 5mm)
you can find the specs here
http://www.giroud2.com/download/ledring.xls
I do not think i will use it since i am pretty happy with the ring with 5050 Leds.
I ordered just the leds (300x 5050 warm white and 300x 5050 cold white) $0.15 per led.
The goal is to build a BIG ring made out of an aluminum ring.
Reason is the angel eye rings are great but too small for an EX1 with the original mattebox.
to mount even the biggest ring (140mm diam) you need to remove the mattebox.
So i planned to glue 63 Leds on the big ring (see picture)
http://www.giroud2.com/download/ring.jpg
, so more light (the biggest angel eye ring has only 49 leds), easier to install, and more solid.
if you own a small camera, or if you do not have a huge plastic sunshade, the angel eye is great. You just glue one or two on a filter ring (UV for example) fitting your camera.
I tested with the 120mm inside the 140mm, and it gives a lot of light, enough to make your subjet grin.

What is that substance you used to attach the hotshoe mount to the ring and are you sure it will stay? Unless you weld the two, I would be concerned that for metal to metal, any other method than welding would have a tendency to break loose.

the substance is expoxy glue (2 components). I will use the same glue to fix leds on the ring.
it is ok to make it rock solid, because (you don't see it on the top, but you can see it at the bottom) the hinge is going through the ring by a slot. the glue is just there to fill the space. My original plan was to add a screw, but it is really not necessary.