Rick
The ring light uses 20x 5mm dia high brightness "white" LEDs. Mine are Vf3.3v If 20mA.
Each one is fed by a 470 ohm 1/4W resistor - you may need a different value if you choose different type of LED.
As far as the PCB layout is concerned it does not matter which way round the LEDs are soldered in as long as they are all the same way round.
It is powered by 12v DC with the polarity connected to suit which way round you fitted the LEDs. It takes about 350 mA at 12volts DC and I power mine from a small switched mode power supply but almost anything that will supply the current will do.
I fitted the LEDs just proud of the board so as to allow for some adjustment - it is surprising how directional they are. It probably does not matter for mill illumination but for photography (which was its original purpose) it is more important to get even illumination.
I fitted mine in a plastic housing turned from a piece of 1 inch thick sheet and fitted a diffuser to improve the evenness and to protect the circuitry.
(I cant take the diffuser off the show the PCB because it is glued in place)
I attach it to the mill with Velcro, it is fortunate that it fits nicely over the spindle and I can still use it on the camera if I wish.
