Olympus BHM Microscope LED Light

The BHM microscope that I bought recently was fitted with a light source that was an incandescent bulb. It is driven by a variable transformer PSU. The PSU is quite nice, the bulb not so much. I have a suspicion that the bulb is a replacement that isn't quite the right voltage as it has never been more bright than a bit dim. I decided to build an LED replacement, so ordered some Cree LEDs and set about making a mount for them.

I had a cylinder I had cast from some melted down scrap, and turned it to the diameter of the lamp holder that fits on the back of the microscope.
After it was the correct diameter I drilled some holes that will hold the LED into place:

 The LED is then fixed in place with three screws:

The cylinder acts as a heat sink. I had bread-boarded the circuit and checked how hot the circuit and LED got and it doesn't get very hot at all. It's a 1W LED so there's not a lot of scope for dissipation. The connections for the LED run in a milled channel down the cylinder. I put a block of aluminium on the end as a mounting plate for the circuitry and as extra heat-sinking outside of the light holder.

The PSU outputs a.c. which is fine for the bulb but not so good for the LED. I added a bridge rectifier, some dropper resistors and a capacitor to convert the a.c. to a d.c. supply. This mounts on the block on the end of the assembly. Initially I used bits of wire to connect the circuitry to the PSU:

3D printed stand-offs hold the circuit board away from the aluminium block:

I wasn't very happy with using bits of wire to connect the PSU and didn't fancy hunting around for a suitable connector, so I made one. I turned a couple of pins from phospher bronze:

And 3d printed a shell in two parts. The pins have a shoulder that holds them in to the shell. The pins turned out nicely:

Here's the light in place and generating photons. The LED is positioned very close to the position the bulb filament would have been in and I end up with a pretty even illumination across the field of view.

 The light and the connector look like this when assembled:

I may add bolts to hold the connector together, but the pins are a tight fit so I may not. Here's the original bulb in it's holder as a comparison:

The LED leads are soldered across a capacitor for now, I'll tidy them up later. Once I've run this for a while I'll  make a PCB to mount the components anyway, so this is probably temporary.

I've got a descriptive video of this LED illumination here: