stereomicroscope illumination for less than $10

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iconoclastica
Posts: 179
Joined: Sun Jan 20, 2019 5:43 pm

stereomicroscope illumination for less than $10

#1 Post by iconoclastica » Sat Oct 22, 2022 7:54 pm

Either my eyes get worse or the amount of light of my now 'bout 15 years old led ringlight is decreasing (possibly both). But since some time I 've been growing increasingly discontent with the illumination levels beneath my stereo microscope. Another source of annoyment was that the brim of the ring light sank some 2cm below the bottom of the objective, as such decreasing the working distance with the same 2cm. And I use this distance to work in indeed.
Also since I bought this mic I have been wanting a more directional illumination than the flat light produced by the ring light. The latter still has to wait some time, but while looking for options of how to make that, I remembered that inside ceiling lamps nowadays there's often a circular series of LEDs and that they produce a bucket of light. Browsing the infamous AliExpress website, it turned out such rings can be bought separately in a variety of diameters and wattages. I couldn't fathom why, but the search term is "angel eyes":
"2W-12W angel eyes led cob light source annual shape 12V DC 20mm-120mm"
"2W-12W angel eyes led cob light source annual shape 12V DC 20mm-120mm"
led rings.jpg (75.03 KiB) Viewed 2115 times
Making a microscope light from one of these seemed no more complicated than selecting the proper diameter, mounting it and adding power. It turned out to be that simple.
I selected the smallest diameter that would fit over the objective. Mind that the advertised diameter is the outer diameter. So to get ring with an inner diameter >65mm (Leica) I bought the 90 mm ring LED (7.15 euros).
Mounting the ring requires some creativity. I used the 3d-printer to make a ring that slides over the objective lens. It had some design flaws, so I won't post the files here. There are many solutions to the problem though, e.g. proper-sized pvc-pipe. If you don't mind quick and dirty, adhesive tape will do the job.

To drive a led, you'll need a constant current power source and you'll need to know how many amperes the led can have. More amperes means more light, too many amperes though means a smoking led and no light. If the current/ampere rating is not given, dividing the voltage by the wattage will usually do. Mine was properly documented, the Allowable maximum current being 900mA. Sometimes you can find a single unit led driver with the parameters (voltage, current) you need, but I couldn't. Therefore, I took a leftover power adapter of a flatbed scanner (12V, 20W) and throttled the output with an adjustable constant current module. To adjust, connect both, power up, short the output of the cc-module with the amperemeter and turn the screw until the current drops below the LED's rating. I chose a conservative 0.75A and left it at that.

does it work?
Yes, and how nicely so! The light levels at the object are twice that of the old ring light. The ring does not get hot, hardly warm even. It still runs at about 80% of its maximum rating. This produces sufficient light and possibly extends its life span. I appreciate the extra space for my hands. The two-modules driver train allows for a dimmer. I would have made that too, if it hadn't been for the postman who decided that my address doesn't exist and sent the package back to China.

There was even an unexpected bonus. When I acquired this microscope, some 15 years ago, I also bought the 1.6x plan apo objective. It had been sitting on the shelf ever since, for it has half the working distance of the standard 1x objective. So the old ringlight sank almost to the table top and hardly any light reached the object. Now, with the highr-up LED ring, a lot of light falls onto the object and the 1.6 objective finally turnes out to be the marvellous lens I once hoped it would be. It extends the magnification range from 50x to 80x (which is the maximum, more needs a sturdier stand than I can use).

a few pictures:
_WDW0189.jpg
_WDW0189.jpg (53.65 KiB) Viewed 2115 times
_WDW0190.jpg
_WDW0190.jpg (69.43 KiB) Viewed 2115 times
_WDW0191.jpg
_WDW0191.jpg (27.27 KiB) Viewed 2115 times

Scarodactyl
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Re: stereomicroscope illumination for less than $10

#2 Post by Scarodactyl » Sat Oct 22, 2022 10:42 pm

Very nice! "Angel eyes" are actually meant to go around headlights in cars, at least that is where the term comes from. I'll admit it's a pleasant surprise it doesn't need heat sinking (since of course it's important that the objective not become the heat sink). I might need to try this--I can only fit so many 150w halogen light sources on my desk.

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iconoclastica
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Re: stereomicroscope illumination for less than $10

#3 Post by iconoclastica » Sun Oct 23, 2022 11:06 am

The 3d-printed sleeve around the objective physically separates the LED-ring entirely from the objective. If the LEDs ever would heat up, the PLA would melt first and the whole contraption fall down.

Scarodactyl
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Joined: Sat Mar 03, 2018 9:09 pm

Re: stereomicroscope illumination for less than $10

#4 Post by Scarodactyl » Sun Oct 23, 2022 4:49 pm

iconoclastica wrote:
Sun Oct 23, 2022 11:06 am
The 3d-printed sleeve around the objective physically separates the LED-ring entirely from the objective. If the LEDs ever would heat up, the PLA would melt first and the whole contraption fall down.
It's a good safety mechanism.

dtsh
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Location: Wisconsin

Re: stereomicroscope illumination for less than $10

#5 Post by dtsh » Sun Oct 23, 2022 11:05 pm

Nice job! The ones I got were not as bright as I would like, but they work fairly well.

Here's a thread where I designed one for use with the Cycloptic. There are some changes I would make were I to build another, but last I spoke with it's caretaker it was still working fine for her. I was fairly proud of how the 3D housing came out.

viewtopic.php?f=12&t=12102

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iconoclastica
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Re: stereomicroscope illumination for less than $10

#6 Post by iconoclastica » Mon Oct 24, 2022 1:00 pm

dtsh wrote:
Sun Oct 23, 2022 11:05 pm
Nice job! The ones I got were not as bright as I would like, but they work fairly well.

Here's a thread where I designed one for use with the Cycloptic. There are some changes I would make were I to build another, but last I spoke with it's caretaker it was still working fine for her. I was fairly proud of how the 3D housing came out.

viewtopic.php?f=12&t=12102
Well designed, especially the protection of the wire, the vunerability of which I had not foreseen and resolved to hot glue. Maybe I'll redo the printing now i now the heat is not an issue at all.

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