Dead Simple BH2 LED Mod <$150

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josmann
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Dead Simple BH2 LED Mod <$150

#1 Post by josmann » Thu Dec 23, 2021 1:44 am

Hey folks - I want to make a more detailed video on this and I will at some point, but I also want to get the results so far out there so that anyone who can figure out a bit of basic electronics hobbying themselves can try it out too.

Basically all this comes down to is a set of off-the-shelf parts from Amazon that happen to work quite simply to punch a ton of high quality light through a BHT or BHTU base. In my case, I'm getting about 150% more light than a max brightness halogen base and a lot more than that if you like to use a daylight filter. I don't know if it's as much as a BHS, probably not, but it's a huge improvement for peak brightness and affords me a lot more ISO headroom when doing video at high magnifications.

First, here are a set of images of my diatom test slide comparing brightness between two BHTU bases. I was using an AAC condenser set to NA.60, the same SPlan 40x objective, and the same trinocular head, photo eyepiece, and camera (with fully manual settings - static shutter speed and WB) for each image. Basically I had the illuminators at full blast on each stage and ported all the parts over without reconfiguring them (aside from focus and centering) to get the same shots on each. Mis-focused the diatoms for the halogen lamp, sorry! The filename of each image describes the settings:
LED - Koehler - ISO100.jpg
LED - Koehler - ISO100.jpg (45.81 KiB) Viewed 4611 times
LED - ISO100.jpg
LED - ISO100.jpg (61.88 KiB) Viewed 4611 times
Halogen - Koehler - ISO100.jpg
Halogen - Koehler - ISO100.jpg (32.7 KiB) Viewed 4611 times
Halogen - ISO100.jpg
Halogen - ISO100.jpg (50.69 KiB) Viewed 4611 times
Halogen - DaylightFilter - ISO100.jpg
Halogen - DaylightFilter - ISO100.jpg (39.8 KiB) Viewed 4611 times
Last edited by josmann on Thu Dec 23, 2021 3:44 am, edited 3 times in total.
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josmann
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Re: Dead Simple BH2 LED Mod <$150

#2 Post by josmann » Thu Dec 23, 2021 1:45 am

Pics continued:
Halogen - ISO250.jpg
Halogen - ISO250.jpg (54.02 KiB) Viewed 4610 times
Halogen - DaylightFilter - ISO500.jpg
Halogen - DaylightFilter - ISO500.jpg (56.27 KiB) Viewed 4610 times
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Re: Dead Simple BH2 LED Mod <$150

#3 Post by josmann » Thu Dec 23, 2021 2:06 am

Attached is a photo of the critical parts shopping list from amazon. You will also need soldering supplies and a 5V DC power supply for the cooler fan (I dug an old wall wart out of my junk drawer). Mount the LED on the cooler with some thermal paste or epoxy, connect it to the output of the boost converter, connect the power supply to the input of the boost converter. Power the cooler fan. Configure the boost converter for max voltage and min current (turn voltage limit pot all the way counterclockwise, current all the way clockwise). Configure the DC power supply for 30V output limit and 3A input (ensuring a maximum of 90W out can never be exceeded). Turn on the power supply and the LED should come on dimly. Turn the CC pot counterclockwise to increase the brightness - you can watch the current draw on the DC power supply tick up (it should operate in CC mode the whole time). The boost converter is certainly not 100% efficient so it's prudent to tape it to a heatsink (it has an aluminum base). A judicious electronics hobbyist should be able to figure out the maximum wattage the DC power supply can supply to still maintain less than 100W to the LED to reach the absolute maximum. To be safe (read: lazy), I always keep the benchtop supply regulating at <100W. Note that if you try to power on the LED while it's configured for high brightness, the protection circuitry of the benchtop supply will freak out and it'll flicker and buzz. Turn the CC pot all the way down before you power on.

The great thing about this is the heatsink mount and lens have a nearly-glovelike fit into the rear lamp port - just plunk it on the table with the fins oriented vertically and it'll slide right into the back. I haven't noticed any overheating issues even though the fins are partially blocked like this. The cooler stays just warm to the touch even after extended operation. Note that we're definitely throwing out a lot of light here - the coupling is nowhere close to optically ideal and there's certainly room for improvements. But it's nice to be able to throw a few things together in an hour or so and get a ton more light through your BH2 - with a stable color temperature to boot! One thing I want to try is removing the initial diffuser in the illuminator assembly. I think it may not be necessary and could substantially improve the throughput if removed.

The LED used here is a high CRI module which has a very natural daylight color temperature. I actually used this same module to light this video: https://www.youtube.com/watch?v=kkdIQZX-LJo by cranking it up and shooting it at the ceiling. When you're underneath it, it really does feel like there's a skylight above you!
amazon shopping list.PNG
amazon shopping list.PNG (352.66 KiB) Viewed 4606 times
IMG_8238.jpg
IMG_8238.jpg (109.27 KiB) Viewed 4606 times
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Re: Dead Simple BH2 LED Mod <$150

#4 Post by woyjwjl » Fri Mar 18, 2022 9:31 am

Is the filament position strictly controlled?
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Re: Dead Simple BH2 LED Mod <$150

#5 Post by josmann » Wed May 04, 2022 6:06 am

woyjwjl wrote:
Fri Mar 18, 2022 9:31 am
Is the filament position strictly controlled?
On the BH2 filament position does not matter. The first surface the light hits is a diffuser and then it is lensed to a second diffuser. The true light source beginning the Koehler system is the white disk of light at the second diffuser. This makes the BH2 very forgiving to illuminate.
Last edited by josmann on Tue May 17, 2022 12:06 am, edited 1 time in total.
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Re: Dead Simple BH2 LED Mod <$150

#6 Post by Sure Squintsalot » Mon May 16, 2022 3:55 pm

I like this and will likely do something similar on my optiphot.

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Re: Dead Simple BH2 LED Mod <$150

#7 Post by josmann » Tue May 17, 2022 12:12 am

Sure Squintsalot wrote:
Mon May 16, 2022 3:55 pm
I like this and will likely do something similar on my optiphot.
I recently picked up this power supply: https://www.amazon.com/gp/product/B07MZ ... UTF8&psc=1

to replace the benchtop unit. I just leave the pot dialed in for the max I was using with the benchtop supply and use neutral density filters if I need to cut the light down.
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PeteM
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Re: Dead Simple BH2 LED Mod <$150

#8 Post by PeteM » Tue May 17, 2022 2:01 am

Jason - thanks for this detailed and useful post (just now seen). The original cobb LED seems no longer available on Amazon. Curious if it continues to work well and would be worth seeking out elsewhere?
Last edited by PeteM on Tue May 17, 2022 3:35 am, edited 1 time in total.

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Re: Dead Simple BH2 LED Mod <$150

#9 Post by Sure Squintsalot » Tue May 17, 2022 3:34 am

Why not just just disassemble a 120v AC dimmable LED bulb to fit behind the collector and connect it all to a Lutron dimmer switch? Total cost: maybe $50? And potentially simpler.

I'd like to get an entire package with cooling to fit within that black box, though. I suppose I'll try that. At any rate, it's super cool that you've shown the concept to be entirely workable!

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Re: Dead Simple BH2 LED Mod <$150

#10 Post by josmann » Tue May 17, 2022 3:13 pm

PeteM wrote:
Tue May 17, 2022 2:01 am
Jason - thanks for this detailed and useful post (just now seen). The original cobb LED seems no longer available on Amazon. Curious if it continues to work well and would be worth seeking out elsewhere?
Hi Pete, I think this is the same one: https://www.ebay.com/itm/284306351789?h ... BMrL7QqJpg

It still works extremely well. I’ve been live streaming DIC microscopy in 1080p 60fps on Twitch and switching from the standard tungsten lamp to this dramatically improved my broadcast quality. I can properly expose 400x magnification at 1/125s using an ISO of just 2000. The light is also useful as a general purpose illuminator for macro/stereoscope imaging. I call it my “****-off bright LED” because it’s so outrageously intense. It actually warms up the base of the BH2 about as much as the tungsten lamp which probably means it’s terribly inefficient and you could probably get away with a smaller one but as I said in the post, the goal here is overkill.
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Re: Dead Simple BH2 LED Mod <$150

#11 Post by josmann » Tue May 17, 2022 3:16 pm

Sure Squintsalot wrote:
Tue May 17, 2022 3:34 am
Why not just just disassemble a 120v AC dimmable LED bulb to fit behind the collector and connect it all to a Lutron dimmer switch? Total cost: maybe $50? And potentially simpler.

I'd like to get an entire package with cooling to fit within that black box, though. I suppose I'll try that. At any rate, it's super cool that you've shown the concept to be entirely workable!
I like the idea - let me know if you find an LED fixture that works for this. I think it would need to be a spotlight of some kind - a normal LED bulb won’t be as densely bright and directed as this. And then I’m not sure how heat sinking it would work - these high power density LEDs definitely need to be cooled.
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Re: Dead Simple BH2 LED Mod <$150

#12 Post by Sure Squintsalot » Tue May 17, 2022 4:36 pm

josmann wrote:
Tue May 17, 2022 3:16 pm
Sure Squintsalot wrote:
Tue May 17, 2022 3:34 am
Why not just just disassemble a 120v AC dimmable LED bulb to fit behind the collector and connect it all to a Lutron dimmer switch? Total cost: maybe $50? And potentially simpler.

I'd like to get an entire package with cooling to fit within that black box, though. I suppose I'll try that. At any rate, it's super cool that you've shown the concept to be entirely workable!
I think it would need to be a spotlight of some kind - a normal LED bulb won’t be as densely bright and directed as this. And then I’m not sure how heat sinking it would work - these high power density LEDs definitely need to be cooled.
Correct....and funny you should mention. About 7 years ago, I retrofitted a modern LED into an old overhead fan/lighting fixture. The halogen light was simply too dim:

Crappy halogen fixture to be replaced
Crappy halogen fixture to be replaced
FAXMQ4SIVO5FTMH.jpg (29.25 KiB) Viewed 3568 times
New, modern LED. 2400 Lumens- HOLY COW!....notice that it will NOT fit.
New, modern LED. 2400 Lumens- HOLY COW!....notice that it will NOT fit.
FKRWUBCIVO5FSQ7 (1).jpg (72.67 KiB) Viewed 3568 times
Start taking apart the light. Be careful.
Start taking apart the light. Be careful.
FRO6CN0IVO5GLEH.jpg (18.51 KiB) Viewed 3568 times
After disassembly, it'll look like this.
After disassembly, it'll look like this.
Screenshot 2022-05-17 102554.jpg (132.93 KiB) Viewed 3568 times
Now, it's Dremel time. Attach a simple abrasive cut-off wheel for cutting into aluminum and plastic. I separated the actual lamp from the driver behind it.
The potted driver. I'm holding it by the screw-in base.
The potted driver. I'm holding it by the screw-in base.
Screenshot 2022-05-17 103157.jpg (111.92 KiB) Viewed 3568 times
More follows, below:

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Re: Dead Simple BH2 LED Mod <$150

#13 Post by Sure Squintsalot » Tue May 17, 2022 4:46 pm

Then, I carefully unpotted the driver with a shallow cut through the plastic base. Much easier than it sounds:
Screenshot 2022-05-17 103341.jpg
Screenshot 2022-05-17 103341.jpg (89.89 KiB) Viewed 3568 times
FLIHL1EIVO5FZ7M.jpg
FLIHL1EIVO5FZ7M.jpg (10.63 KiB) Viewed 3568 times
Then I unpotted the driver:
FCW3XNKIVO5FZ8J.jpg
FCW3XNKIVO5FZ8J.jpg (10.72 KiB) Viewed 3568 times
The "pot" is an elastic, silicone-based compound that, thankfully, doesn't stick to the PCB or components. So, it's easily removable with basic dental tools, or forceps:
Screenshot 2022-05-17 104326.jpg
Screenshot 2022-05-17 104326.jpg (97.63 KiB) Viewed 3568 times
Once unpotted, it'll look like this:
Screenshot 2022-05-17 104501.jpg
Screenshot 2022-05-17 104501.jpg (126.13 KiB) Viewed 3568 times
You don't necessarily need to unpot the driver. I had space constraints, and unpotting the driver made it much smaller and easier to fit.

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Re: Dead Simple BH2 LED Mod <$150

#14 Post by Sure Squintsalot » Tue May 17, 2022 4:59 pm

Now, I had to put the LED on a heat sink. I simply modified the housing/sink it was attached to with a Dremel, cutting off the fins and other extraneous bits:
Screenshot 2022-05-17 105006.jpg
Screenshot 2022-05-17 105006.jpg (125.41 KiB) Viewed 3564 times
Screenshot 2022-05-17 105113.jpg
Screenshot 2022-05-17 105113.jpg (162.57 KiB) Viewed 3564 times
...and got to work modified the the new heat sink. Again, size was a constraint and I had to use the back of the original heat sink:
Screenshot 2022-05-17 105422.jpg
Screenshot 2022-05-17 105422.jpg (118.65 KiB) Viewed 3564 times
Sanding flat, and very smooth, the new heat sink using 600 grit wet sandpaper.
Screenshot 2022-05-17 105525.jpg
Screenshot 2022-05-17 105525.jpg (75.05 KiB) Viewed 3564 times
Slathering heat conducting thermal paste onto the back of the new heatsink:
Screenshot 2022-05-17 105845.jpg
Screenshot 2022-05-17 105845.jpg (59.68 KiB) Viewed 3564 times
More below....

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Re: Dead Simple BH2 LED Mod <$150

#15 Post by Sure Squintsalot » Tue May 17, 2022 5:22 pm

Reassembly....
Screenshot 2022-05-17 110207.jpg
Screenshot 2022-05-17 110207.jpg (116.67 KiB) Viewed 3563 times
Driver and lamp test. I wrapped the driver in a protective shrinktube so that none of it would make contact with its metal container (kinda important).
Screenshot 2022-05-17 110319.jpg
Screenshot 2022-05-17 110319.jpg (105.76 KiB) Viewed 3563 times
Back into the fixture; see my space constraints?
Screenshot 2022-05-17 110607.jpg
Screenshot 2022-05-17 110607.jpg (83.14 KiB) Viewed 3563 times
and, voila!
Screenshot 2022-05-17 111810.jpg
Screenshot 2022-05-17 111810.jpg (90.23 KiB) Viewed 3563 times
Screenshot 2022-05-17 111901.jpg
Screenshot 2022-05-17 111901.jpg (36.4 KiB) Viewed 3563 times
This off-the-shelf LED modification to retrofit into an existing halogen fixture has been working flawlessly since it's installation. I plan to make a similar modification to my Optiphot system, once it arrives in the next month, or so. Hopefully I'll get it to fit within the existing components, perhaps with the added installation of a cooling fan for the LED itself.

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imkap
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Re: Dead Simple BH2 LED Mod <$150

#16 Post by imkap » Tue May 17, 2022 9:08 pm

I just ordered some LED's for my Zeiss GFL, this time a few Cree branded from Mouser, hopefully they will work better than the one I have currently. I found the choice in the 18V range is quite broad and not expensive 5-10€ a piece, I'm going to fit them inside the microscope and see how much light can I get without overheating... I'll post something when I see the results.
The external lights like the one josmann made should be better as you can cool them however you want. But that will wait, as I don't have much time to make it lately and it would make my microscope a bit bulkier. I like the small foot on my GFL...
Sure Squintsalot wrote:
Tue May 17, 2022 5:22 pm
This off-the-shelf LED modification to retrofit into an existing halogen fixture has been working flawlessly since it's installation. I plan to make a similar modification to my Optiphot system, once it arrives in the next month, or so. Hopefully I'll get it to fit within the existing components, perhaps with the added installation of a cooling fan for the LED itself.
Nice work on the ceiling lamp...

I wouldn't plug the 120/240v AC directly into my scope, it seems a bit dangerous as there is a lot of touching involved, although if done properly it should be OK I suppose, but still an unnecessary risk... Working with low DC seems safer, especially for amateurs...

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