A Luxeon ringlight for microscope

Don Foreman wrote in news: snipped-for-privacy@4ax.com:

Nice;you should put your LED drive circuitry schematic on the site.

We've been making microscope ringlights for years now, of various wavelengths. Sometimes we even use two wavelengths, designed for selective fluorescence. They make great illuminators, if you keep in mind the illumination angle of the LEDs and place enough of them around in a circle. Full overlap is a good idea. We wire the LEDs in series, plus a ballast resistor, and power them from HP 6216B, etc., power supplies bought on eBay. Works like a charm.

I didn't want a source as diffuse as a ring of many LED's because I was quite dissatisfied with an Aristo fluorescent ringlight. I wanted the higher contrast of only four 1-watt Luxeons with good collimation. I still have ample diversity of direction for killing shadows and softening specular reflections, but the contrast is markedly better. My use is low-magnification (2.5x to 22.5x) for surfacemount work. One 1-watt Luxeon is equivalent in output to about 20 high-brightness 5mm LED's.

OK. Maybe tomorrow. It's just four straightforward right-off-the-app-note current sources using sections of an LM324, a gumdrop transistor (2N4404) and an emitter sense resistor with feedback from the sense resistor. Volts in from pot of 0 to 0.5 gives collector current of 0 to about 330 mA with a 1.5 ohm sense resistor. The supply is just a "simple switcher" set up for about 4.75 volts, capable of 1.5 amps.

Still want a schematic?

Four Luxeon LEDs with 90-degree spacing?

Contrast is a function of light intensity.

Have been trying to come up with extra bright LED's to take the place of quartz lamps. The trouble is getting proper focus and coverage into one small area. This is for fluorescence. The quartz lamp is in back of a lens thats reflected with a mirror.

greg

Nice! Both the concept and the construction are wonderful.

Ed

I suppose a joystick could also be used for trimmers.

greg

Hmmm. Tropical daylight is more like 100K lux...a small point Paul Mathews

Have look at Lamina in Digikey catalog.

Regards,

Boris Mohar

Got Knock? - see: Viatrack Printed Circuit Designs (among other things)

void _-void-_ in the obvious place

Yes, about 2" radially from the objective barrel axis.

Right you are. I thought I corrected that. Got footcandles and lux mixed up. It is more like 0.3 x tropical sunlight.

It's still pretty bright. Look at the webpage again ... I added a photo of the light spot on the bench in presence of other illumination.