Experimentations with high powered LEDs for microscope illumination

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billbillt
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Re: Experimentations with high powered LEDs for microscope illumination

#31 Post by billbillt » Fri May 29, 2015 7:35 pm

Yep.. I will get one... I have to wait awhile before I can spend anymore money right now.... I will also get a PWM controller like the one you have...

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Crater Eddie
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Re: Experimentations with high powered LEDs for microscope illumination

#32 Post by Crater Eddie » Sat May 30, 2015 12:59 am

Excellent! I'll be interested in your results and observations.
CE
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Re: Experimentations with high powered LEDs for microscope illumination

#33 Post by The QCC » Sat May 30, 2015 6:21 pm

I have had a mixed experience with hi-power LEDs for microscope illumination.
I am presently on my fourth unit. The previous three have all been returned for credit due to the same problem.
When the LED power is increased to maximum or near maximum a Venetian blind effect is visible in the image.
I assumed a power supply filtration problem, but the effect was still there when I used a 12V battery.

The current unit seems to have eliminated the problem most of the time.

This is unit is similar to the current illuminator.
The LED came with the cradle and a tint tripod
The LED came with the cradle and a tint tripod
10wLED-2.jpg (55.14 KiB) Viewed 15251 times
[/url]
Unfortunately, listings on eBay are very transient and the unit with a cradle and mini-tripod is no longer available.

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Re: Experimentations with high powered LEDs for microscope illumination

#34 Post by Crater Eddie » Sat May 30, 2015 11:04 pm

It seems odd that the effect is noticed at or near full brightness rather than minimum. I assume that this shows up in recorded videos and not still images.
CE
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Re: Experimentations with high powered LEDs for microscope illumination

#35 Post by The QCC » Sat May 30, 2015 11:41 pm

No the effect shows up in stills and videos.

The blind effect starts around half power, disappears and the reappears near maximum power.
The effect almost looks like it is beating with sub harmonic of the Canon camera's frame rate. I do not know if non-Canon cameras have the same issues with high power LEDs.

One supplier of high power LED's I communicated with stated there was a large batch of substandard LEDs released to the market. Coupled with no LED driver other than a variable DC supply it is not surprising I had problems.

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Re: Experimentations with high powered LEDs for microscope illumination

#36 Post by Crater Eddie » Sun May 31, 2015 12:40 am

Interesting. I have to think that it's a function of the supply voltage rather than the LED itself, be it some PWM fuzz or rectifier ripple in the dc supply. Either way, some variation in LED brightness beating against some component of the camera sampling rate is what causes this banding from what I understand. Do some cameras use different sampling rates than others? Probably so, this would explain why some illuminators work fine for some folks and cause banding for others. It seems that the only perfect solution would be to use a battery for the supply (no rectifier ripple) and an adjustable linear circuit of some kind (no PWM fuzz) to vary the brightness. Not very efficient, not very handy, but it would eliminate the banding artifacts for once and for all.
CE
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75RR
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Re: Experimentations with high powered LEDs for microscope illumination

#37 Post by 75RR » Thu Jun 04, 2015 11:45 am

PWM Dimmer and 3 Ohm 50W Wirewound Resistor as shown/demonstrated on TV (well video anyway) by Crater Eddie now on way.
ETA about 5 weeks
Zeiss Standard WL (somewhat fashion challenged) & Wild M8
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Re: Experimentations with high powered LEDs for microscope illumination

#38 Post by Crater Eddie » Tue Jun 09, 2015 2:26 pm

75RR wrote:ETA about 5 weeks
Shipping from China is weird, sometimes it's very slow, and sometimes it's faster than you expect. My 3 ohm resistors arrived yesterday, took just a tad over two weeks.
CE
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billbillt
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Re: Experimentations with high powered LEDs for microscope illumination

#39 Post by billbillt » Tue Jun 09, 2015 2:40 pm

Yep, I have noticed the same thing... They must have different modes of shipping like we do...

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Re: Experimentations with high powered LEDs for microscope illumination

#40 Post by Crater Eddie » Thu Jun 18, 2015 4:11 pm

Update:
The 3 ohm 50 watt Chinese resistor works just fine. It still dissipates a fair amount of power as heat though, since this is a fairly inefficient circuit, so if you plan to go this route you will want to consider mounting the resistor on a heat sink.
I have used this setup for a few hours now, and must say that that for a cheap knock-up it works very well.
Taking the lamp house apart to reposition the LED, I noticed a fair amount of room under the lamp assembly, I think I can fit a small brushless CPU fan in there to keep the LED cool. This is probably not strictly necessary, but hopefully it will help prolong the LED life a bit as I know it runs hot. It will make me feel better anyway. The fan runs very smoothly, but if I can I'll mount it on rubber bands to help dampen any vibration. I think there is room, if not I can just leave it on top of the lamp house where it is now, though it does not move as much air in that position.
CE
Last edited by Crater Eddie on Fri Jun 19, 2015 12:30 pm, edited 1 time in total.
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Re: Experimentations with high powered LEDs for microscope illumination

#41 Post by Crater Eddie » Thu Jun 18, 2015 4:49 pm

The QCC wrote:No the effect shows up in stills and videos.

The blind effect starts around half power, disappears and the reappears near maximum power.
The effect almost looks like it is beating with sub harmonic of the Canon camera's frame rate. I do not know if non-Canon cameras have the same issues with high power LEDs.

One supplier of high power LED's I communicated with stated there was a large batch of substandard LEDs released to the market. Coupled with no LED driver other than a variable DC supply it is not surprising I had problems.
Earlier I missed where you said you had run it from a battery with the same results.
My apologies.
This confirms that in your case the artifacts were caused by the controller or the LED itself. I hope you get this sorted out.
CE
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LOMO BIOLAM L-2-2
LOMO POLAM L-213 / BIOLAM L-211 hybrid
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Re: Experimentations with high powered LEDs for microscope illumination

#42 Post by 75RR » Thu Jun 18, 2015 5:12 pm

I think there is room, if not I can just leave it on top of the lamp house where it is now, though it does not move as much air in that position.
Is this the LOMO Biolam L-2-2 Lamp House?
I was just looking at it in the My microscope section, it occurred to me that rather than blow air down towards the hot LED it might work better if the air is drawn out away from the heat by reversing the fan, bringing cooler air in at the bottom.
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Re: Experimentations with high powered LEDs for microscope illumination

#43 Post by Crater Eddie » Thu Jun 18, 2015 5:27 pm

Yes, the L-2-2.
Sitting on top of the lamp house the fan pulls air up from the bottom, through the lamp house, past the LED heat sink, and out the top. I thought it might cool a little better putting it on the bottom and blowing up, thereby pressurizing the lamp house somewhat instead of depressurizing it. I don't know that it would really make that much difference in the cooling, but if it muffled the sound of the fan a bit that would be a plus.
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Re: Experimentations with high powered LEDs for microscope illumination

#44 Post by Crater Eddie » Fri Jun 19, 2015 3:14 am

Yep. Moving the fan to the bottom of the lamphouse increased the air flow by quite a bit. Now I'm happier anyway.
CE
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Re: Experimentations with high powered LEDs for microscope illumination

#45 Post by 75RR » Fri Jun 19, 2015 11:40 am

Yep. Moving the fan to the bottom of the lamphouse increased the air flow by quite a bit. Now I'm happier anyway.
Any chance of an image of the fan in position? Curious about the fan as well.
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Re: Experimentations with high powered LEDs for microscope illumination

#46 Post by Crater Eddie » Fri Jun 19, 2015 1:18 pm

It's not much to look at, but I'll take a couple photos tonight since you asked.
The fan was too big to hang inside the opening at the bottom of the lamphouse like I wanted, so I ended up attaching it to the bottom on the outside instead.
With the fan sitting on top pulling air through, I could barely feel any air coming out of it at all... with it on the bottom and blowing air through, there is plenty of air movement. In fact, running it at half speed still moves more than enough air, and is much quieter too.
CE
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Re: Experimentations with high powered LEDs for microscope illumination

#47 Post by 75RR » Fri Jun 19, 2015 1:38 pm

It's not much to look at, but I'll take a couple photos tonight since you asked.
Sorry, did not mean to put you out. Your description will do very well. Thanks
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Re: Experimentations with high powered LEDs for microscope illumination

#48 Post by Crater Eddie » Fri Jun 19, 2015 1:47 pm

Oh, no problem at all! I just meant that it's not pretty, rubber bands and tape... not much to look at. :lol:
CE
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Re: Experimentations with high powered LEDs for microscope illumination

#49 Post by Crater Eddie » Sat Jun 20, 2015 12:24 am

Image

Here is my LED cooling system, pretty sophisticated. Note the high tech variable tension mounting system.
Looks like the cello tape blew off.


Image

A small strip of tissue paper secured over the louvers dances in the breeze to remind me that the fan is on when running at low speed. At about half speed it's almost silent (it's running here, hence the dancing tissue). With the fan on the top the tissue barely stirred, even at full speed. I think the louvers being so close to the blades interfered with the air feed too much.


Image

The fan adds about half an inch to the bottom of the lamp house so I had to shim the scope up to provide clearance. I really need a taller chair. I'm looking for a smaller fan, one that will fit into the bottom opening so I can claim that half inch back.
In the background you can see the charger indicating that my lamp supply battery is now fully charged and ready for another viewing session.
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Re: Experimentations with high powered LEDs for microscope illumination

#50 Post by 75RR » Sat Jun 20, 2015 1:04 am

Thanks for the photos.
It actually looks quite small, are there smaller ones?
Did you add heat sink compound when you joined the LED to the heat sink?
Those theoretical 50 000 rated life hours probably only apply inside a refrigerator.
Temp sensor would be great!

Like your windsock.
Zeiss Standard WL (somewhat fashion challenged) & Wild M8
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Re: Experimentations with high powered LEDs for microscope illumination

#51 Post by Crater Eddie » Sat Jun 20, 2015 1:30 am

Yes, I did use heat sink compound, though it is a pretty wimpy heat sink hence my concern. I have a better one on its way from China. They do make much smaller fans. I have one somewhere that should fit like I want it to, I just haven't looked in the right box yet.
CE
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Re: Experimentations with high powered LEDs for microscope illumination

#52 Post by Crater Eddie » Thu Jun 25, 2015 2:16 pm

So, what good is all this fooling around anyway? Most serious hobbyists will buy a good scope with a good working illumination system and not bother with all these shenanigans.
Sure.
But, some day you might find a good deal on a nice scope and all that's wrong with it is the circuit board or transformer in the illuminator is toast. Or maybe next time you fire up your $$$$ scope all you will get is a puff of smoke and darkness. It's always good to know that you CAN do stuff like this if you want to, or need to.
Besides, it's fun.
CE
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Re: Experimentations with high powered LEDs for microscope illumination

#53 Post by lorez » Thu Jun 25, 2015 4:17 pm

CE,
serious hobbyists
The beauty of having a hobby is that you can pursue it in any way you choose and that is what makes it better for a group such as this.

Everyone has a little different interest and in sharing add to the understanding of the rest of us.

Thanks for sharing your enthusiasm and experiences.

lorez

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Re: Experimentations with high powered LEDs for microscope illumination

#54 Post by billbillt » Thu Jun 25, 2015 4:21 pm

It is very FUN... It is so inexpensive that a person can try many variations of lighting with very little outlay... LED is a very useful and doable replacement for halogen lighting...

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Re: Experimentations with high powered LEDs for microscope illumination

#55 Post by The QCC » Thu Jun 25, 2015 9:56 pm

Crater Eddie:

What wattage of halogen lamp did you replace with your 10w LED light source?

I tried a 10W LED in my Labomed LB-592 with dismal results. The Labomed has a 100w (2000 lumen) halogen lamp.
By my calculations, I would need a 25w LED replacement.
I have a Gossen light meter with a microscope attachment and the 100w halogen produces 1400 lumens with a 40x obj. and 1600 lumens with a 2x obj.
The 10w LED with the 40x obj. just barely reached 200 lumens and with the 2x obj. 400 lumens.

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Re: Experimentations with high powered LEDs for microscope illumination

#56 Post by gekko » Thu Jun 25, 2015 10:09 pm

The QCC wrote:I have a Gossen light meter with a microscope attachment and the 100w halogen produces 1400 lumens with a 40x obj. and 1600 lumens with a 2x obj.
CE and The QCC, sorry to intrude: may I ask what battery you use with your Gossen and where do you get it? The mercury cells are no longer available.
The QCC wrote:By my calculations, I would need a 25w LED replacement.
Would something like this work:
http://www.cree.com/LED-Components-and- ... mp-CXA1310
http://www.cree.com/LED-Components-and- ... mp-CXA1507

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Re: Experimentations with high powered LEDs for microscope illumination

#57 Post by The QCC » Thu Jun 25, 2015 11:25 pm

Gekko:

My first replacements for the mercury battery came from Gossen in Germany. They provided a small conversion kit and two silver oxide batteries.
I recently have started using E625G manganese oxide batteries.
REPLACES EPX625

The Cree CXA1310 looks interesting. I downloaded several application notes. I will read them and see if any ideas pop up.

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Re: Experimentations with high powered LEDs for microscope illumination

#58 Post by Crater Eddie » Thu Jun 25, 2015 11:28 pm

The original bulb is a 100w halogen bulb. I haven't had any shortage of light so far using the 10w LED, but I have only used it with the lower power objectives (4x, 8x, and 20x). You raise a good point, I need to check it out with the 40x and 100x objectives to see how it holds up. I have used the 20x objective with the LOMO Optivar set on 2.5x and had plenty of light, so I'm optimistic about use with the 40x objective. I'm currently working on getting all my alignments straightened out, when I get that sorted I'll do some testing.
CE
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Re: Experimentations with high powered LEDs for microscope illumination

#59 Post by gekko » Fri Jun 26, 2015 10:32 am

The QCC wrote:I recently have started using E625G manganese oxide batteries.
REPLACES EPX625
Thank you, The QCC (apologies to CE for momentarily changing the subject).

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75RR
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Re: Experimentations with high powered LEDs for microscope illumination

#60 Post by 75RR » Fri Jun 26, 2015 10:39 am

Crater Eddie wrote: You raise a good point, I need to check it out with the 40x and 100x objectives to see how it holds up.
Perhaps a light intensive illumination technique such as Darkfield would also be useful.
Zeiss Standard WL (somewhat fashion challenged) & Wild M8
Olympus E-P2 (Micro Four Thirds Camera)

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