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

#91 Post by billbillt » Sun Jul 12, 2015 4:16 pm

Hi Eddie,
The PS I bought provides 5 amps... I have a 50W 6.8 ohm resistor here I planned to use... What I love about this LED stuff is that it is so cheap that a person can try a vast number of combinations for little cash outlay...

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Re: Experimentations with high powered LEDs for microscope illumination

#92 Post by Crater Eddie » Sun Jul 12, 2015 5:24 pm

Oh, I see. I thought maybe you were using the 3 amp power supply that you mentioned some time back.
As long as you limit the current to something the LED can handle it should work fine.
CE
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Re: Experimentations with high powered LEDs for microscope illumination

#93 Post by billbillt » Sun Jul 12, 2015 6:03 pm

I thought about the 3 amp, but opted for the 5.. There was only a few bucks difference...

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

#94 Post by 75RR » Mon Jul 13, 2015 1:28 am

Crater Eddie wrote:75RR:

I didn't see your edit until just now. As long as that works for you it should be fine. The only issue you might have, the dimmer might not be as stable at the lower input, that is it might be struggling. I would run some video tests to check for artifacts. If you don't see any banding creeping in then you are good to go. If you find that you have to run at one of the higher settings you could always place a filter in the light path to tone it down, maybe crossed polarizers or something. Again, not efficient, but a workable solution.
You mentioned putting everything in a box to tidy it up, that is a good idea. If you take the cover off the dimmer you will see that the potentiometer has a fairly long cable on it, this is to allow you to separate it from the dimmer and mount it remotely.
Just remember to allow for good air flow through the enclosure, you don't want things over heating. I would mount the power resistor on the outside to allow for convection cooling. If you really want it hidden inside the enclosure it would be best to add a cooling fan.
Mindful of your point about stability I am using what I think might be a Neutral Filter (hope so anyway), got it in a batch of assorted filters.
40mm diameter, silvered mirror finish says N 16 on it. Not Zeiss as they are 32mm so not sure what it is.
Shutter speed goes from 8 to 15 when I add it. It allows me to view the iris in order to focus it and also center the condenser without being blinded. This LED is bright!
Still a little worried about UV rays. Filter I got is too large, still looking for someone to cut a 32mm disc out of it.
Touched the Resistor, thought it would be warm, but no, the word is hot.
Wanted to include it in the box in order to tidy things up. Perhaps if it has some ventilation it might be ok.
The idea is to use banana connectors. Keep it neat and tidy.

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Re: Experimentations with high powered LEDs for microscope illumination

#95 Post by Crater Eddie » Mon Jul 13, 2015 3:52 am

Yes, the resistor gets hot, I tried to make that point several times.
If you put it inside the box you really need to include a fan, otherwise you are going to wind up with a pretty hot box.
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Re: Experimentations with high powered LEDs for microscope illumination

#96 Post by 75RR » Mon Jul 13, 2015 4:06 am

Post deleted.
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Re: Experimentations with high powered LEDs for microscope illumination

#97 Post by Crater Eddie » Mon Jul 13, 2015 4:30 am

Oh. Well, in that case, I deleted my reply.
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Re: Experimentations with high powered LEDs for microscope illumination

#98 Post by 75RR » Mon Jul 13, 2015 11:35 am

Oh. Well, in that case, I deleted my reply.
Sorry. Began calculating Watt differential and tied myself in knots.

What are your calculations on the Nominal 6V with the LED?
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Re: Experimentations with high powered LEDs for microscope illumination

#99 Post by Crater Eddie » Mon Jul 13, 2015 12:46 pm

Nominal 6V setting on Power Supply
IN Range 7.7V - 7.31V
OUT Range 1.79V - 3.38V
OUT Range (Incl. Resistor) 1.92V - 2.78V
Current Range 0.01A - 0.29A


If I'm running the numbers correctly (hopefully someone will chime in if I have pulled a boner here, I haven't had my coffee yet this morning), this is 2.11 watts total; the LED is running at about .8 watts, so the resistor is dissipating 1.31 watts.
Everything should run a lot cooler. If this is really all the power you need, and you don't get any artifacts in the stills or video, then you're golden.
You could use a cheaper lower power LED if you wanted to.
Now that I think about it, I usually observe with the control turned most of the way down, only using higher intensities when shooting video since my USB camera demands a lot of light.
CE
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Re: Experimentations with high powered LEDs for microscope illumination

#100 Post by billbillt » Mon Jul 13, 2015 3:43 pm

I have had good luck with the cheap Chinese star LEDS up to 5 watts.... I have no complaints about the performance of these units.... They can usually be bought for next to nothing on Ebay...

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Re: Experimentations with high powered LEDs for microscope illumination

#101 Post by 75RR » Mon Jul 13, 2015 5:07 pm

Thanks Crater Eddie
... this is 2.11 watts total; the LED is running at about .8 watts, so the resistor is dissipating 1.31 watts.
That is what I got so you see why I thought it was wrong.
Have to use a Neutral filter with 8,10 and 12V which effectively slashes the output - seems a little counter intuitive.
This is based on page 5 of the LED's PDF, added some pretty colours to it.
Using the Nominal 6V looks a little silly!
If the higher voltages had a lower range everything would be fine, well apart from a little extra heat.

Image

Just ran the LED at Nominal 6V for 30 min, resistor cool to the touch!
Then ran the LED at Nominal 8V for 30 min, resistor burnt my finger!
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Re: Experimentations with high powered LEDs for microscope illumination

#102 Post by Crater Eddie » Mon Jul 13, 2015 5:55 pm

The next thing to do is to snap some stills and take some video at this input level at a good range of intensity settings. Don't worry about having everything perfect, just see if you get any artifacts. If the stills and video are clean then your problem is solved.
Like I said before, a heat sink on the resistor will help it dissipate the heat, will keep it from getting so hot.
If it turns out that the 6v range works ok then you don't have to worry about heating.
CE
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Re: Experimentations with high powered LEDs for microscope illumination

#103 Post by 75RR » Mon Jul 13, 2015 6:47 pm

Is there anyway to extend the lower range of the 8,10 and 12V output?
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Re: Experimentations with high powered LEDs for microscope illumination

#104 Post by Crater Eddie » Mon Jul 13, 2015 7:04 pm

I don't remember if there are any trimmers (adjustments) on the controller or not. If there are, then it might be possible to turn it down a bit. I'll take the cover off mine tonight and see.
Another way to extend the low range would be to use a higher value limiting resistor. Since you have an extra, you could wire it in series with the one in use and see if that helps. This would also cut down on your high range though.
CE
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Re: Experimentations with high powered LEDs for microscope illumination

#105 Post by 75RR » Mon Jul 13, 2015 8:46 pm

Another way to extend the low range would be to use a higher value limiting resistor. Since you have an extra, you could wire it in series with the one in use and see if that helps. This would also cut down on your high range though.
Ok. Tried it. This is what I got.

Nominal 8V
IN .............10.88V - 9.74V
OUT............ 2.16V - 9.40V
OUT + R.......1.97V - 3.01V
Current.........0.02A - 0.95V

Image
Last edited by 75RR on Mon Jul 13, 2015 8:56 pm, edited 1 time in total.
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Re: Experimentations with high powered LEDs for microscope illumination

#106 Post by Crater Eddie » Mon Jul 13, 2015 8:49 pm

How was the light level?
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Re: Experimentations with high powered LEDs for microscope illumination

#107 Post by 75RR » Mon Jul 13, 2015 8:57 pm

How was the light level?
Lower but still a little high.
See graph I added to previous post.

Received two suggestions to extend range:

http://www.ebay.com/itm/201059502388?ru ... 26_rdc%3D1

http://www.ebay.com/itm/171396563942?ru ... 26_rdc%3D1
I haven't tried this, but how about feeding something like ebay item 201059502388 from a simple power supply.
On the face of it you twiddle the pot to dim the led by current control, so with the pot taken out to a panel it would appear to be able to cover the whole range without the range changing, or the resistor.
The resistor is costing you volts, so it sould be good to lose it.

You might need ferrite beads on the pot wires to stop oscillation, maybe.
And I'm not sure how warm it would get.

Or ebay 171396563942 ?
Got another suggestion:
http://www.ledsupply.com/led-drivers/bu ... led-driver
+ pdf:
http://www.ledsupply.com/content/pdf/le ... tation.pdf
There are so many driver possibilities, but this would be my personal choice, either the 1400ma or 2100ma. (I realize that these can be driven up to 3000ma but unless you absolutely need to, it generates a lot more heat for a modest light level boost).
Would any of these work?
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Re: Experimentations with high powered LEDs for microscope illumination

#108 Post by Crater Eddie » Mon Jul 13, 2015 11:05 pm

Probably.
The first one is a lot like the module we used on the 3 watt LED project.
There are no adjustments on my controller board, so I can't help any further with that.
I honestly never expected "too much light" to be the problem.
CE
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Re: Experimentations with high powered LEDs for microscope illumination

#109 Post by Crater Eddie » Tue Jul 14, 2015 1:38 am

The second one looks interesting, but there doesn't seem to be any way to adjust the output, there are no controls evident.
The third one looks real good. This is the one I would pick. It looks easy enough to hook up. You wouldn't get full brightness out of the 10 watt LED, but that doesn't seem to be an issue.
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Re: Experimentations with high powered LEDs for microscope illumination

#110 Post by 75RR » Tue Jul 14, 2015 11:25 am

The third one looks real good. This is the one I would pick. It looks easy enough to hook up. You wouldn't get full brightness out of the 10 watt LED, but that doesn't seem to be an issue.
Hi, Was just looking at it. Would it start at 0%, 5% or 10% of LED range or would it (like the one I have now) start at 25%, 50% or even at 100%?
My present dimmer goes all the way down to off, smoothly - problem is the starting point of the led.
Looking at the diagrams on page 3 I am not sure this is different.
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Re: Experimentations with high powered LEDs for microscope illumination

#111 Post by Crater Eddie » Tue Jul 14, 2015 1:50 pm

Hmmm... That's what the graph seems to indicate. Looking over the data sheet it says in a couple of places that the dimming goes from 0% to 100%. Did they get lazy making the graph, or did they exaggerate in the description?
Unfortunately, we are trying to do something here that most users of these devices don't care about, so there is little support for it and scanty data.
Unless you can find someone who has used this module in this manner, the only way to know for sure is to try one and see.
I'll try searching for discussions of the module, maybe I can find some mention of the dimming action.
CE

Edit:

I sent a question to LEDSUPPLY asking about this. We will see what they say.
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Re: Experimentations with high powered LEDs for microscope illumination

#112 Post by 75RR » Tue Jul 14, 2015 2:03 pm

Looking over the data sheet it says in a couple of places that the dimming goes from 0% to 100%.
Saw that and thought that sounded Ok, then I saw the graph.
Think maybe when they say 0% - 100% they are referring to the fact that the Controller is Dimmable throughout its range.
Problem is the ranges are:
0.8A - 1A
1.1A - 1.4A
1.7A - 2.1A
Edit:

I sent a question to LEDSUPPLY asking about this. We will see what they say.
Just saw this. Good idea.
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Re: Experimentations with high powered LEDs for microscope illumination

#113 Post by Crater Eddie » Tue Jul 14, 2015 2:21 pm

Here is the reply from LEDSUPPLY (they were very prompt):

"Thank you for emailing. The BuckBlock will dim the LED down to 5% output, any lower adjustment and the LED will turn off. The dimming is smooth from 100% down to 5%."
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Re: Experimentations with high powered LEDs for microscope illumination

#114 Post by 75RR » Tue Jul 14, 2015 2:43 pm

Do you have a copy of the question you asked them?

It might be easier to have just one person asking questions.

Could you ask them if the ranges of their controllers are:

0.8A - 1A
1.1A - 1.4A
1.7A - 2.1A

Thanks
Last edited by 75RR on Tue Jul 14, 2015 2:49 pm, edited 1 time in total.
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Re: Experimentations with high powered LEDs for microscope illumination

#115 Post by billbillt » Tue Jul 14, 2015 2:44 pm

That sounds like better performance than the Chinese PWM units we have bought...

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Re: Experimentations with high powered LEDs for microscope illumination

#116 Post by Crater Eddie » Tue Jul 14, 2015 2:49 pm

75RR wrote:Do you have a copy of the question you asked them?
"I am interested in using "The LuxDrive™ A009 series BuckBlock™ LED power modules" in a project but have a question about the dimming feature. Using the potentiometer connection shown in the data sheet, will the LED be dimmed smoothly from max intensity down eventually to full dark, or will it only dim down so far then suddenly switch off? The graphs on the data sheet seem to support the latter scenario. Each module will be used to drive a single high power LED from a set DC source.
Thank you for your assistance."
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Re: Experimentations with high powered LEDs for microscope illumination

#117 Post by 75RR » Tue Jul 14, 2015 2:51 pm

Crater Eddie wrote:
75RR wrote:Do you have a copy of the question you asked them?
"I am interested in using "The LuxDrive™ A009 series BuckBlock™ LED power modules" in a project but have a question about the dimming feature. Using the potentiometer connection shown in the data sheet, will the LED be dimmed smoothly from max intensity down eventually to full dark, or will it only dim down so far then suddenly switch off? The graphs on the data sheet seem to support the latter scenario. Each module will be used to drive a single high power LED from a set DC source.
Thank you for your assistance."
My dimmer dims to full dark, shouldn't the question really be what is the Amp range?
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Re: Experimentations with high powered LEDs for microscope illumination

#118 Post by Crater Eddie » Tue Jul 14, 2015 2:52 pm

billbillt wrote:That sounds like better performance than the Chinese PWM units we have bought...
It does, but remember that it will not go up to full brightness. That could be an issue for high magnification use, especially with a finicky camera.
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Re: Experimentations with high powered LEDs for microscope illumination

#119 Post by Crater Eddie » Tue Jul 14, 2015 2:54 pm

75RR wrote:My dimmer dims to full dark, shouldn't the question really be what is the Amp range?
Sorry, I misunderstood your problem. You are certainly welcome to email them and ask.
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Re: Experimentations with high powered LEDs for microscope illumination

#120 Post by 75RR » Tue Jul 14, 2015 3:06 pm

Did not explain myself properly. Unfamiliar with terms.
My dimmer, say with the Nominal 12V Output goes from 0% to 100% of the Controller range at that voltage.
The problem is that the range is 0.7A to 2.75A, so that when it dimms the LED down to 0% of the range,
the LED is still too bright at 0.7A = 100% Relative Luminous Flux (See Chart above)
Even 25% Relative Luminous Flux at 0.2A is very bright. 0.1A is a good lower range.
Was looking for something from 0.1A to say 1.5A
Dimming that range from 0% to 100% would be ideal.

P.S. Have sent email asking for the range of their 3 controllers.
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