Adjusting light intensity, internal, remote or something else?

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dtsh
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Adjusting light intensity, internal, remote or something else?

#1 Post by dtsh » Thu Feb 02, 2023 1:20 am

I've put a few LEDs on AO10's (mostly) and I've gone with a few different methods for mounting the dial to adjust intensity as the design has evolved. I'm curious to hear what others think and perhaps get some suggestions I hadn't considered.

In my first iteration I put the dial in the foot of the scope, it works, but was occasionally in the way; more importantly, it took a lot of effort to install. In later iterations I 3D modeled a small housing to screw onto the back of the scope to hold the user-interfacing parts. Here's a link to my first and subsequent design for anyone wanting to see pictures of microscopes I've mangled.

I've thought a few times of designing a remote, perhaps something like a puck which would hold the dial and perhaps the power jack with a smallish cable leading back into the microscope to power the LED. An advantage of this would be zero modification of the microscope, no drilling, no tapping, but it would no longer be fully self-contained. I tend to dislike remote parts and try to put it all together so things don't get separated and lost, but I'm not sure that's a significant concern.

What do you guys think, would a remote on say 8"/200mm of flexible cable seem comfortable or do you think the adjustment should be secured to the instrument? It would allow for the adjustment to be readily available for either hand by placing it one side or the other.

macnmotion
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Re: Adjusting light intensity, internal, remote or something else?

#2 Post by macnmotion » Thu Feb 02, 2023 3:07 am

When I modified my microscope from AC to DC, I bypassed the built-in voltage adjustment dial and added my own in a separate box which I set right next to the scope, where I can easily adjust voltage by moving my hand from the focus knob where it usually rests. I did this for a couple of reasons. First, I didn't want to hack into the scope, and wanted to be able to easily return it to original condition if I ever wanted to. And second, because this is halogen and I have heard it's good to run the bulb at full intensity every once in a while to maintain the halogen cycle, I set up the switches on the box to be able to bypass the dimmer (the dimmer, even at full power, doesn't allow the same power as direct). Of course this box could be smaller, but I used what we had already. And it takes up a bit of extra room on the table. In my setup that's not an issue. I used male/female plugs which allows easy disconnection from the box if I have to move the scope.
dimmer box outside of box.jpg
dimmer box outside of box.jpg (129.34 KiB) Viewed 4531 times

jfiresto
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Re: Adjusting light intensity, internal, remote or something else?

#3 Post by jfiresto » Thu Feb 02, 2023 9:51 am

+1. You can also refine a separate box after you get a chance to use it, and not worry about further wear and tear on the microscope.

You may find a small, sloped console box to be to your liking. Here is one that houses something different and perhaps more complex, a remote shutter / USB switch, I built, to adapt an E-PL8 mirrorless system camera to fixed use on a microscope:

camera_tether_box.jpg
camera_tether_box.jpg (114.03 KiB) Viewed 4506 times

The five cables, terminating with five plugs and sockets, run straight toward the back of the table.
-John

dtsh
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Re: Adjusting light intensity, internal, remote or something else?

#4 Post by dtsh » Thu Feb 02, 2023 2:08 pm

Those look nice, it is interesting to see the solutions of others to similar issues.
I know manufacturers have, but is anyone using linear pots instead of rotary?

apochronaut
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Re: Adjusting light intensity, internal, remote or something else?

#5 Post by apochronaut » Fri Feb 03, 2023 12:42 pm

I am still curious about these retrofits. I have tried various led illumination options but have been unable to achieve an illuminated field that does not have a Portland lens effect. Extra brightness, especially at lower power consumption is nice but at the expense of contrast and defenition it isn't nice.
Since you have the halogen version of the 10, how does the led retrofit compare to those?
My experience with the 17.8 watt tungsten series 10 is that properly filtered and collimated, it will perform within a shade of the 20 watt halogen. Easily enough for all of the phase objectives and all but the one in DF.
Regarding the remote power supply, one of the supposed detractions of the tungsten illumination system. AO had a bracket/made a version for bench mounting under, on the side or on the wall so to liberate bench space. It seems there is no real gain with a remote pot for an led.

dtsh
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Re: Adjusting light intensity, internal, remote or something else?

#6 Post by dtsh » Fri Feb 03, 2023 7:27 pm

apochronaut wrote:
Fri Feb 03, 2023 12:42 pm
I am still curious about these retrofits. I have tried various led illumination options but have been unable to achieve an illuminated field that does not have a Portland lens effect. Extra brightness, especially at lower power consumption is nice but at the expense of contrast and defenition it isn't nice.
Since you have the halogen version of the 10, how does the led retrofit compare to those?
My experience with the 17.8 watt tungsten series 10 is that properly filtered and collimated, it will perform within a shade of the 20 watt halogen. Easily enough for all of the phase objectives and all but the one in DF.
Regarding the remote power supply, one of the supposed detractions of the tungsten illumination system. AO had a bracket/made a version for bench mounting under, on the side or on the wall so to liberate bench space. It seems there is no real gain with a remote pot for an led.
I've had a couple of halogen equipped AO10's and it's a good instrument, but the one I use is LED equipped; it's the first one I converted, with the potentiometer embedded in the foot. I'm not sure I have the skills to evaluate between them, but for my purposes it's been enough to do brightfield, phase, and darkfield. I don't have any hard numbers, but I feel like it is brighter than the halogen and significantly more intense than the tungsten lamps. I don't currently have any halogen AO10's to compare with, so I can't do an apples to apples comparison.

I believe that chip/driver combo for the first design is pushing around 6w; the chip can handle more, but the driver is the limitation. I'm currently working on another one that's running at 33.2v and consuming just over 0.3amps, so just over 10w, but there's much work to be done on that one until then.

I've sought to keep as much of the electronics inside the scope to keep down on the footprint. I think the 110 would possibly be a better platform at only a slightly larger footprint, but I don't have any 110 trinocular heads.

jfiresto
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Re: Adjusting light intensity, internal, remote or something else?

#7 Post by jfiresto » Fri Feb 03, 2023 9:52 pm

dtsh wrote:
Fri Feb 03, 2023 7:27 pm
... I believe that chip/driver combo for the first design is pushing around 6w; the chip can handle more, but the driver is the limitation. I'm currently working on another one that's running at 33.2v and consuming just over 0.3amps, so just over 10w, but there's much work to be done on that one until then....
I am wondering about the LED heat sinking. For 300mA @ 36V into the COB LED I have on order, Cree recommends less than 4–5K of thermal resistance between case and a 55 deg C ambient (the red, middle line below).
Attachments
COB thermal resistance.gif
COB thermal resistance.gif (22.95 KiB) Viewed 4318 times
-John

Chas
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Re: Adjusting light intensity, internal, remote or something else?

#8 Post by Chas » Fri Feb 03, 2023 10:29 pm

I have tried various led illumination options but have been unable to achieve an illuminated field that does not have a Portland lens effect. Extra brightness, especially at lower power consumption is nice but at the expense of contrast and defenition it isn't nice.
Is it possible that the 'secret structure' of an incandescent filament could act to increase the contrast in some way ??
In the following pic it is not so secret a structure! [focused on a phase annulus]:
Filament 640.jpg
Filament 640.jpg (43.3 KiB) Viewed 4304 times

dtsh
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Re: Adjusting light intensity, internal, remote or something else?

#9 Post by dtsh » Sat Feb 04, 2023 6:01 am

jfiresto wrote:
Fri Feb 03, 2023 9:52 pm
dtsh wrote:
Fri Feb 03, 2023 7:27 pm
... I believe that chip/driver combo for the first design is pushing around 6w; the chip can handle more, but the driver is the limitation. I'm currently working on another one that's running at 33.2v and consuming just over 0.3amps, so just over 10w, but there's much work to be done on that one until then....
I am wondering about the LED heat sinking. For 300mA @ 36V into the COB LED I have on order, Cree recommends less than 4–5K of thermal resistance between case and a 55 deg C ambient (the red, middle line below).
The CMT1412 I have is doing decently with a 25mm x 25mm x 15mm heatsink. I have left it on for a couple of hours as I'm testing to get stable temperatures, but this one hasn't been put into an instrument yet.
Specs state 38v max, 34v typical; mine is running at 33.2v down to just above cutoft to keep heat manageable.

Chas wrote:
Fri Feb 03, 2023 10:29 pm
I have tried various led illumination options but have been unable to achieve an illuminated field that does not have a Portland lens effect. Extra brightness, especially at lower power consumption is nice but at the expense of contrast and defenition it isn't nice.
Is it possible that the 'secret structure' of an incandescent filament could act to increase the contrast in some way ??
In the following pic it is not so secret a structure! [focused on a phase annulus]:

Filament 640.jpg
With it in focus at that point it should be out of focus at the image plane, no?

jfiresto
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Re: Adjusting light intensity, internal, remote or something else?

#10 Post by jfiresto » Sat Feb 04, 2023 9:40 am

dtsh wrote:
Sat Feb 04, 2023 6:01 am
The CMT1412 I have is doing decently with a 25mm x 25mm x 15mm heatsink. I have left it on for a couple of hours as I'm testing to get stable temperatures, but this one hasn't been put into an instrument yet.
Specs state 38v max, 34v typical; mine is running at 33.2v down to just above cutoff to keep heat manageable.
I would be curious what LES temperatures you are measuring: Cree implies around 140C for the recommended maximum 7W/K thermal resistance, both for Ta=55C. I will be trying Cree's latest CMA1516 Pro9 over 31~500mA. I hope the "Pro" proves to be more than marketing.
-John

dtsh
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Re: Adjusting light intensity, internal, remote or something else?

#11 Post by dtsh » Sat Feb 04, 2023 4:14 pm

jfiresto wrote:
Sat Feb 04, 2023 9:40 am
dtsh wrote:
Sat Feb 04, 2023 6:01 am
The CMT1412 I have is doing decently with a 25mm x 25mm x 15mm heatsink. I have left it on for a couple of hours as I'm testing to get stable temperatures, but this one hasn't been put into an instrument yet.
Specs state 38v max, 34v typical; mine is running at 33.2v down to just above cutoff to keep heat manageable.
I would be curious what LES temperatures you are measuring: Cree implies around 140C for the recommended maximum 7W/K thermal resistance, both for Ta=55C. I will be trying Cree's latest CMA1516 Pro9 over 31~500mA. I hope the "Pro" proves to be more than marketing.
I'll be the first to admit that I barely know what I am doing and can easily get into areas where I'm fully ignorant. The temperatures are what I get at various points on the cob, heatsink, etc while it's running and have been trying to keep the highest I measure under 50C. When I install one into a microscope, I turn it on at the start of the day at the highest output and check it every 30 minutes or so until there's no significant variation between the last 3 or 4 checks. With the prototype, I left it on for 8 or 9 hours which is far more than I have ever used it for.

GerryR
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Re: Adjusting light intensity, internal, remote or something else?

#12 Post by GerryR » Sat Feb 04, 2023 8:10 pm

I posted this sometime ago concerning what I did to modify my 1031 illuminator to LED for my AO 10:
https://www.microbehunter.com/microscop ... 28&t=16425

I had to drop the current down to 25% (~ 0.50 A) so the brightness was manageable and still use the ND filter. I was able to install everything in the 1031 frame after gutting it out and use a 12vdc external brick supply for power. Heating is not an issue at this level of current. I have only used it for bright-field and have no idea if it is sufficient for phase or DF. It might give you some ideas as to setup.

jfiresto
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Re: Adjusting light intensity, internal, remote or something else?

#13 Post by jfiresto » Mon Feb 06, 2023 8:58 am

dtsh wrote:
Sat Feb 04, 2023 4:14 pm
The CMT1412 I have is doing decently with a 25mm x 25mm x 15mm heatsink. I have left it on for a couple of hours as I'm testing to get stable temperatures.... [They] are what I get at various points on the cob, heatsink, etc while it's running and have been trying to keep the highest I measure under 50C. When I install one into a microscope, I turn it on at the start of the day at the highest output and check it every 30 minutes or so until there's no significant variation between the last 3 or 4 checks. With the prototype, I left it on for 8 or 9 hours which is far more than I have ever used it for.
Thank you for those numbers. These COB LEDs generate much more heat than I have had to deal with, so just getting a sense of what is typical is a big help.
-John

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