# Microscope LED conversion: Incandescent VS LED questions from newb



## cincin (Jan 24, 2016)

Greetings!

I'm trying to convert my trusty Swift microscope to LED bottom illumination. I'm new to LEDs and electronics in general, so I have a few questions that'll likely be very easy for you guys to answer:

My scope currently uses a 30w incandescent lightbulb. I read somewhere that incandescent bulbs produce about 20 lumens per watt, so the current setup is probably near 600 lumens.

I want to replace the incandescent system with a brighter, natural or cool white > 5000K, dimmable and rechargeable LED system.

I want the light source to be brighter than the current setup (so more than 600 lumens) but I don't want to overdo it because of heat concerns.

By my online research it seems I would need about a 10w LED to produce approx. 1000 lumens. Does that sound right??

Staring at my 3v LED flashlight (which seems VERY bright) I can't help but to think I'd be scorching my retinas staring through a scope at a 10w LED.... thus my doubts, and my question.

Thanks for the help!!


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## FRITZHID (Jan 25, 2016)

Welcome to cpf!!!

1st off, in a microscope application, I'd recommend a high CRI LED, such as Nitcha 219b. Proper color rendition would seem a priority in that application, imho.
2nd, what kind of power source is available?
3rd, will there be any diffusion or collimator material between LED and whatever you're looking at? LEDs have a very wide angle and lots of useful light could be wasted.
You might easily get away with less LED wattage if it's focused properly.
4th, what kind of space is available for LED, heatsinking and driver/control?
Pics would help allot.


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## mds82 (Jan 25, 2016)

yes post a few picture of what the setup looks like and i'm sure someone here can help out. as fritzhid said, are there any optics between the bulb to focus it?


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## cincin (Jan 25, 2016)

Thank you both!

1: I agree, I'm looking for a high CRI setup if possible. But coming from incandescent illumination, LEDs are already a great step towards better color rendition. So if I have to compromise here it won't hurt much.

2: The current incandescent setup plugs into the wall at at 110-120v in north america. I'm hoping for a rechargeable setup that uses a battery that gives me a couple hours of independence no more. The battery pack can charge from 120v or USB, whatever is easiest. Ideally the scope would be usable while charging.

3: There's a collimating lens in front of the light source that concentrates the light into a straight beam that then goes into the condenser which turns it into a cone of light that focuses on the subject. There's a reflector behind the bulb (not visible in the photo since it's screwed to the lid). I was considering setting up a better reflector that covers the sides for the LED, to save all the stray photons but also to make the light source "look" bigger. Keeping in mind that the current 30w incandescent bulb gets focussed just the same then I think comparing lumens to lumens still works (if my understanding of lumens in LED vs incandescent is correct)?

4: Here's a photo of the underbelly of the scope. I have a bout 3cm of clearance in height, except for where the bulb is, I have 4.5cm in height in that 3cm round hole. 

Bonus points if I can reuse the knob for the pot, I'd like to keep everything looking original, other than losing the power cord.

Any and all advice, tips & recommendations most appreciated!


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## FRITZHID (Jan 25, 2016)

cincin said:


> Thank you both!
> 
> 1: I agree, I'm looking for a high CRI setup if possible. But coming from incandescent illumination, LEDs are already a great step towards better color rendition. So if I have to compromise here it won't hurt much.
> 
> ...



1. No, not really. Halogen and/or incandescent is considered to be the best overall in CRI. Some LEDs and/or LED arrays come close but halogen is 100 CRI where as most LEDs don't peak above 90 CRI.

2. Shouldn't be too much of an issue, depending on what LED you ultimately choose, a couple 18650s or 26650s Should do the trick.

3. You probably want a custom or at least tweaked version of what you already have. LEDs throw their light forward at an average of 120° rather than a globe of light 360° as a lightbulb does. A proper reflector would/could do this however I think optics would be better in this application.

4. Reusing some stock components, or at least their outward appearances should not be an issue. May have to change the POT depending on what your driver requires.


This looks like it should be a fairly easy remodel. Heatsinking shouldn't be an issue. Finding a driver that works may be a little tricky. Most use step dimming rather than POT variable. I suggest against a PWM driver unless it has an extremely high pulse frequency, otherwise eye strain may be a serious issue.
Cell control boards (charge/discharge controllers) are easy to find.

Machining parts/fabrication will most likely be involved, Idk what kind of access you have to that, as well as soldering, wiring, electronics, etc skills.


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## cincin (Jan 25, 2016)

FRITZHID said:


> 1. No, not really. Halogen and/or incandescent is considered to be the best overall in CRI. Some LEDs and/or LED arrays come close but halogen is 100 CRI where as most LEDs don't peak above 90 CRI.
> 
> 2. Shouldn't be too much of an issue, depending on what LED you ultimately choose, a couple 18650s or 26650s Should do the trick.
> 
> ...



1. Yeah but the current incandescent bulb is very warm yellow. The scope has a retractable daylight glass filter to make the light a little more neutral, but a neutral light source, lower CRI as it may be, would be better than filtering out the yellow I believe. But yes, high CRI LED it is.

2. I've just added to the original post that ideally the LED would be functional while charging. Not sure if that's an issue or not.

3. Since I lack pretty much all the skills involved in doing this, and also since it seems cheaper to buy a finished product than its components, I was thinking of repurposing a rechargeable headlamp or flashlight. Finding just the right combination of rechargeable, color temperature, power, and dimmable is harder than I'd expected.

Thanks for the insight about PWM drivers! I hate flicker.

So to come back to my original question: Did I get the lumens comparison right? a 30w incandescent is indeed about 60% as bright as a new gen 10w LED?

If that's the case then I might consider a 15w LED setup if that's feasible given the space, heat, power etc. If possible I'd like to get more light out of it than a 60w halogen would spit out. Not for direct brightfield observation, but for darkfield.

I found this but I believe the driver is a PWM: http://lifehacker.com/make-a-super-bright-led-lighting-fixture-you-can-dim-to-1753041003

This item looked promisingly economical for repurposing but it's only about 350 lumens: goo.gl/tAqOtJ

I do have access a workshop, a machinist and a woodworker, I should be able to handle the installation.

I gladly welcome specific combinations of LED, dimmable driver, battery pack and charger. I'm not technically qualified to figure out what will make a good (or even compatible) combination...

Thanks!


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## mds82 (Jan 25, 2016)

Here's my quick and easy though on it for what you can do.

LED- Pick up a Cree XHP-50 LED and use it in a 6V configuration on s standard star board. You can use an optic to focus the light forward, or just leave it bare

Driver - If you want to use a 12V dc input, you can use the LED Dynamics BuckBlock which has the option for a pot dimmer, which you can mount right to side side of the housing. 1000ma driver =950 lumens, 1400ma driver = 1280 lumens, and 2100ma driver gives you 1800 lumens

for a power source you can use a 12 or up 30 v power supply, such as a laptop power supply. Or you can use any a battery source thats 9-30v.

just mount the LED to a large sheet enough piece of aluminum on the bottom with thermal glue. 

should be pretty simple can you can get away with everything for under $30


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## DIWdiver (Jan 25, 2016)

If your bulb is very yellow, then you are probably getting substantially less than 20 lm/W.

One advantage that LEDs have in this application is that they don't radiate light in all directions. All of the light is directed forward, and most of it within a 120 degree cone. Right off, this is a big advantage if the light radiating outside that cone (whether from LED or incandescent) is lost.

Another difference is that the LED is an AREA source rather than a LINE source like a filament bulb. This should help with more uniform lighting.

Another thing you should consider is the LED die size. You probably don't want the die size to be any larger than the length of the filament in your bulb, and probably smaller. Your optics won't focus a large die into a useful area, so if you have 1000 lm in a die 2mm square, it's probably going to provide the same useful light as 4000 lm in a 4mm square die. It may well be that 1mm or less is useful. It seems to me like the width of the filament (which is either helically or helically-helically wound ) may be the limiting size on what's useful lighting area.

it's possible when you consider all these factors that you may find an LED is not a suitable replacement for your light source.


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## cincin (Jan 26, 2016)

mds82 said:


> Here's my quick and easy though on it for what you can do.
> 
> LED- Pick up a Cree XHP-50 LED and use it in a 6V configuration on s standard star board. You can use an optic to focus the light forward, or just leave it bare
> 
> ...



Thanks! That sounds like a good recipe, I'll go shop for the ingredients. Do you guys have a favourite online store?


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## cincin (Jan 26, 2016)

DIWdiver said:


> If your bulb is very yellow, then you are probably getting substantially less than 20 lm/W.
> 
> One advantage that LEDs have in this application is that they don't radiate light in all directions. All of the light is directed forward, and most of it within a 120 degree cone. Right off, this is a big advantage if the light radiating outside that cone (whether from LED or incandescent) is lost.
> 
> ...



Very good points! I'll keep all of that in mind for the final design and assembly.

Converting microscopes to LED is actually a fairly popular thing to do, despite the apparent lack of online literature on the subject... The added brightness (huge advantage for darkfield), reduced heat (doesn't affect your subject), neutral colored light and the convenience of portability makes a lot of sense. A lot of old scopes have fantastic optics but the illumination system is, by today's standards, sub-par.

Cheers for the help!


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## FRITZHID (Jan 26, 2016)

I still think a nitcha 219b is your best bet for LED. Plenty of lumens and best CRI to date.


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## mds82 (Jan 26, 2016)

cincin said:


> Thanks! That sounds like a good recipe, I'll go shop for the ingredients. Do you guys have a favourite online store?



digikey.com has everything in stock. LEDsupply might be a bit cheeper for the buckblock driver though. If you dont know how to mount the LED to the star board i can do that for you as well if you need.


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## cincin (Jan 26, 2016)

FRITZHID said:


> I still think a nitcha 219b is your best bet for LED. Plenty of lumens and best CRI to date.



Those are hard to come by apparently, and as far as I can tell the high CRI versions are all under 600 lumens.

The proposed XHP50 has a CRI of 90 and gives out 780-840 lumens according to digikey:

http://www.digikey.com/product-deta...0UG20E2/XHP50A-01-0000-0D0UG20E2CT-ND/5806095

I'd love to gain an extra 3 CRI but I need at the very least 600 lumens.

There are many high CRI high power LEDs in the 30v operating range, for my application is that not feasible on a rechargeable setup? or not a good idea because of heat?

Thanks for sharing the expertise!


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## mds82 (Jan 26, 2016)

cincin said:


> http://www.digikey.com/product-deta...0UG20E2/XHP50A-01-0000-0D0UG20E2CT-ND/5806095



This led is rated at 5700k so its not going to be as yellow, making the light appear closer to daylight. 
with this LED you can get 1250 lumens at 2100mA, 900 lumens at 1400mA and 660 lumen at 1000mA output. it also goes up to 1650 lumen at 3000mA ( all at a 6V drive setup) 

i just cheked on Digikey to see whats in stock from cree and for 90CRI the xhp50 is the best option. There are other smaller LED's out there but they wont get as many lumens


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## cincin (Jan 26, 2016)

Alright, so again forgive my newby questions, but for this assembly I would need:

1 x LED such as this XHP50 from a "Cut Tape" goo.gl/w4A2WG

1 x Star board (like this one? goo.gl/dspW1D seems to be just for XRE?)

1 x Star shaped thermal tape goo.gl/FXizcO

1 x Heat sink such as this goo.gl/RwMq2b

1 x LED Dynamics BuckBlock goo.gl/TUiCSa

1 x reflector to fit

1 x POT to match the driver

1 x 12v laptop battery & charger

Did I get this right? Are all these parts really compatible?

Thanks!


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## cincin (Jan 26, 2016)

mds82 said:


> This led is rated at 5700k so its not going to be as yellow, making the light appear closer to daylight.
> with this LED you can get 1250 lumens at 2100mA, 900 lumens at 1400mA and 660 lumen at 1000mA output. it also goes up to 1650 lumen at 3000mA ( all at a 6V drive setup)
> 
> i just cheked on Digikey to see whats in stock from cree and for 90CRI the xhp50 is the best option. There are other smaller LED's out there but they wont get as many lumens




Thanks! I just posted the above before seeing your post. I'll edit to reflect the new LED choice.


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## DIWdiver (Jan 26, 2016)

I doubt that the XHP50 is a good choice. It may put out a lot of lumens, but it is comprised of four dies with a gap between them. This may well create a shadow in your lighting. The total emitter surface is also pretty large. Given that your goal is to put lots of light in a tiny area, probably >99% of all those lumens are going to be wasted. I think you'd be better off with a smaller die with a brighter surface, like an XPE2.


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## cincin (Jan 26, 2016)

DIWdiver said:


> I doubt that the XHP50 is a good choice. It may put out a lot of lumens, but it is comprised of four dies with a gap between them. This may well create a shadow in your lighting. The total emitter surface is also pretty large. Given that your goal is to put lots of light in a tiny area, probably >99% of all those lumens are going to be wasted. I think you'd be better off with a smaller die with a brighter surface, like an XPE2.



It's hard to see on the photo but the filament in the incandescent bulb actually covers a good square centimeter of area, so I'm not sure it's too much of a concern. As far as the multiple dies, again I think it's not ideal but it will mimic the filament at worst. In the current setup there's also a 2" reflector that goes behind the bulb, I get the impression from the geometry that it sends parallel light up through the lens, and the focal point is the filament obv. So in the end I think maybe I actually need a larger die, or appropriate reflector to mimic the apparent light source size. But then I may very well be entirely wrong.


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## mds82 (Jan 26, 2016)

cincin said:


> Alright, so again forgive my newby questions, but for this assembly I would need:
> 
> 1 x LED such as this XHP50 from a "Cut Tape" goo.gl/w4A2WG
> 
> ...



Yes to everything but the reflector and the POT. http://www.digikey.com/product-detail/en/A019/788-1083-ND/3114448 leddynamics offer a buidl in dimmer, its not the cheepest but it works well. You can mount this to the side of the microscope so you can adjust the brightness very easily and cleanly. the laptop power supply can be anywhere from 12-30v, and you can even get away with a smaller wall plug in power supply .

For the aluminum heatsink, you will need to play around with this a bit as where to mount the LED to get it to be the most useful. You can even pick up strips of aluminum at home depot whcih might give you more surface area and more width to mount it to, but the heat sink you list there will work for sure

Do you have the ability to mount the LED to the star board, if not PM me and i can do this for you as well. For the thermal tape, you can either use that tape, of if you are doing to do other projects similar you may want to pick up a tube a Arctic Silver Thermal Epoxy. That's a 2 part epoxy you can mix that you can mount the LED board to aluminum.


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## cincin (Jan 26, 2016)

mds82 said:


> Yes to everything but the reflector and the POT. http://www.digikey.com/product-detail/en/A019/788-1083-ND/3114448 leddynamics offer a buidl in dimmer, its not the cheepest but it works well. You can mount this to the side of the microscope so you can adjust the brightness very easily and cleanly. the laptop power supply can be anywhere from 12-30v, and you can even get away with a smaller wall plug in power supply .
> 
> For the aluminum heatsink, you will need to play around with this a bit as where to mount the LED to get it to be the most useful. You can even pick up strips of aluminum at home depot whcih might give you more surface area and more width to mount it to, but the heat sink you list there will work for sure
> 
> Do you have the ability to mount the LED to the star board, if not PM me and i can do this for you as well. For the thermal tape, you can either use that tape, of if you are doing to do other projects similar you may want to pick up a tube a Arctic Silver Thermal Epoxy. That's a 2 part epoxy you can mix that you can mount the LED board to aluminum.



So it has to be one of those special led dimmers then? i was hoping a regular pot with the right resistance range might work, then I could put it where the current POT is and it would look all original from the outside. I guess I might be able to do that with that dimmer, but yeah $25 raises the cost of the project a bit.

Thanks for your installation offer but I believe I can manage by myself, it'll be simpler than shipping it to you then back to me (I'm in Canada). Feel free to give me any tips you're willing to share on how to do it myself. I saw this video on the process: https://www.youtube.com/watch?v=7rNm8lN5YWU but I don't have a hot plate do reflow the solder paste, any tips?


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## mds82 (Jan 27, 2016)

cincin said:


> So it has to be one of those special led dimmers then? i was hoping a regular pot with the right resistance range might work, then I could put it where the current POT is and it would look all original from the outside. I guess I might be able to do that with that dimmer, but yeah $25 raises the cost of the project a bit.
> 
> Thanks for your installation offer but I believe I can manage by myself, it'll be simpler than shipping it to you then back to me (I'm in Canada). Feel free to give me any tips you're willing to share on how to do it myself. I saw this video on the process: https://www.youtube.com/watch?v=7rNm8lN5YWU but I don't have a hot plate do reflow the solder paste, any tips?



with the right pot it should work to dim it, i just dont know what value pot yuu need. to reflow the LED you need to use solder paste and do it carefully otherwise you can ruin the LED.


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## FRITZHID (Jan 27, 2016)

A 3rd hand and a heat gun work equally well to reflow a LED onto a star. Been doing it for years and have never had a failure.
Pull the stock POT off the driver and meter it, then buy the proper resistance POT that will fit in your stock location and wire it in, you'll be fine.


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## cincin (Jan 27, 2016)

FRITZHID said:


> A 3rd hand and a heat gun work equally well to reflow a LED onto a star. Been doing it for years and have never had a failure.
> Pull the stock POT off the driver and meter it, then buy the proper resistance POT that will fit in your stock location and wire it in, you'll be fine.



Brilliant! Any idea what temperature I should have the heat gun at, and how do I know it has "reflown", when to stop? hahahah I know nothing

Thanks guys!


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## FRITZHID (Jan 27, 2016)

cincin said:


> Brilliant! Any idea what temperature I should have the heat gun at, and how do I know it has "reflown", when to stop? hahahah I know nothing
> 
> Thanks guys!



Well, I use the highest heat my gun provides, I hold it about 2-3" from the bottom of the star (LED sitting on top of course) and just watch carefully. You'll see the LED seat itself on the pads as the solder melts and flux starts to bubble, after that, I give it about 5 secs more of heat then switch my gun to cool-down air for a few seconds (10 maybe) then just let the star cool down normally. Just be very careful not to move or bump the LED/star/holder until the solder has hardened to prevent a bad joint.


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## cincin (Jan 27, 2016)

FRITZHID said:


> Well, I use the highest heat my gun provides, I hold it about 2-3" from the bottom of the star (LED sitting on top of course) and just watch carefully. You'll see the LED seat itself on the pads as the solder melts and flux starts to bubble, after that, I give it about 5 secs more of heat then switch my gun to cool-down air for a few seconds (10 maybe) then just let the star cool down normally. Just be very careful not to move or bump the LED/star/holder until the solder has hardened to prevent a bad joint.



Excellent! Thanks for the tips.

I have my doubts that this star board will work: goo.gl/dspW1D

It doesn't say anything about being compatible with the XHP series.

I see SINKPad makes one specifically for the XHP50 in a 6v configuration, but DigiKey doesn't sell it. Would you kindly point me to the best choice of PCB for my purpose?

I just want to make triple sure I order the right parts.


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## cincin (Jan 27, 2016)

Also, any reason I shouldn't go with the Cree XHP70?

goo.gl/IoHg5O

Same operating voltage, same CRI, same color, MORE lumens, HIGHER current (1050mA vs 700mA), slightly bigger die at 7mm (but still smaller than filament area in current bulb).


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## mds82 (Jan 27, 2016)

cincin said:


> Also, any reason I shouldn't go with the Cree XHP70?
> 
> goo.gl/IoHg5O
> 
> Same operating voltage, same CRI, same color, MORE lumens, HIGHER current (1050mA vs 700mA), slightly bigger die at 7mm (but still smaller than filament area in current bulb).



You can go with that LED, its jut more cost and it will probably be overkill for what you are doing. at 2100ma the XHP70 is 1480 lumens whiel the XHP50 is 1250 lumens, at 1000mA they are 770 vs 660 lumens. Not a huge brightness increases for a big cost difference 

goo.gl/dspW1D this will Not work with the XHP 50 LED as its a different pad . http://www.mouser.com/ProductDetail...=sGAEpiMZZMunP6xGBs1h9LwglsmJQmkn7TuHqyL3Wag= This is for the XP Pad which will work for the XHP50 in a 6v configuration. ( which your doing)


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## cincin (Jan 27, 2016)

mds82 said:


> You can go with that LED, its jut more cost and it will probably be overkill for what you are doing. at 2100ma the XHP70 is 1480 lumens whiel the XHP50 is 1250 lumens, at 1000mA they are 770 vs 660 lumens. Not a huge brightness increases for a big cost difference
> 
> goo.gl/dspW1D this will Not work with the XHP 50 LED as its a different pad . http://www.mouser.com/ProductDetail...=sGAEpiMZZMunP6xGBs1h9LwglsmJQmkn7TuHqyL3Wag= This is for the XP Pad which will work for the XHP50 in a 6v configuration. ( which your doing)



And that is why I ask the experts, thank you kindly!


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## mds82 (Jan 27, 2016)

cincin said:


> And that is why I ask the experts, thank you kindly!



sorry i didnt catch that in the first place about the star board


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## cincin (Jan 27, 2016)

mds82 said:


> sorry i didnt catch that in the first place about the star board



No worries at all! I'm just thankful for the help.

Ok, so I can't seem to get all the parts I need in Canada, or even from a single retailer in the US or China... so after taxes & shipping it's adding up to about $130 Canadian for the conversion... the Canadian dollar really sucks right now, that doesn't help.

All Canadian prices:

Mouser
$7.66	1 x Reflector: 928-C12480MIR50SPN
$7.80	1 x tube of solder paste: 557-7459
$1.46	1 x Star board: 951-804511
$3.73	1 x Heatsink: 567-882-50AB

Digikey:
$11.50	1 x LED: XHP50A-01-0000-0D0UG20E2CT-ND
$2.43	1 x Star board thermal tape: 1168-1855-ND
$31.79	1 x Dimmable driver: A009-D-V-2100
$3.00	1 x POT: PTD902-2215K-B203-ND

Ebay.ca
$17.97	1 x 4.8Ah 12V Battery pack & charger: Ebay.ca http://goo.gl/4yGW8r


Mouser: $40.74 CAD incl. $20.00 shipping & taxes
Digikey: $62.57 CAD incl. $8.00 shipping & taxes
ebay.ca: $17.97 CAD incl. $0.00 shipping & taxes

It's a little pricier than expected, but I'm pretty sure it would be a sweet setup...


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## DIWdiver (Jan 27, 2016)

Hmm, seems odd you'd create a large diameter beam to illuminate a microscopic sample. I must be missing something. Based on your description of that bulb, you must be right.

Yes, the switching (in this case buck type) driver is necessary. If you have a 12V battery and a 6V LED, You'd be putting as much power in the pot as in the LED. A pot that would handle that much power directly would be enormous and expensive. Not to mention you'd be throwing away half your battery power.

That's why I don't suggest you use my $25 dimmable driver. Being linear, it would have the same problem as the pot. If you had a 12V LED it would be a lot better, but probably still not as efficient as the BuckBlock.

You can't find equivalents of your Mouser stuff at DigiKey? That would save you the extra shipping charge. 

By the way, that star board is for an XP-G. An XH-P will not fit on it. The XH-P50 will fit on an XM-L star, which would put it in the 6V configuration

That solder paste says it 'flows' between 395 and 430F (202-221C), and 're-melts' at 550F (287C). Most solders for electronics melt at around 217-221C if they are lead free, 180-something for tin/lead. They will do this over and over. I'm not sure what the much higher re-melt temp is all about. I'd want to know more before I attempted to learn soldering with it.


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## cincin (Jan 27, 2016)

DIWdiver said:


> Hmm, seems odd you'd create a large diameter beam to illuminate a microscopic sample. I must be missing something. Based on your description of that bulb, you must be right.
> 
> Yes, the switching (in this case buck type) driver is necessary. If you have a 12V battery and a 6V LED, You'd be putting as much power in the pot as in the LED. A pot that would handle that much power directly would be enormous and expensive. Not to mention you'd be throwing away half your battery power.
> 
> ...



Again, excellent insights!

All the stuff I'm getting from Mouser I could not find equivalent from Digikey. Primarily the star board. Now that you say it won't fit I'm confused, mds82 seems to think it will. I can't find a star board that specifically says it's compatible with the XH-P50 on either Digikey or Mouser...

Shall we take a vote on it? hahaha

Thanks for the help!


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## mds82 (Jan 28, 2016)

DIWdiver is right about the board...  http://www.mouser.com/ProductDetail/Bergquist-Company/804936/?qs=jQRjkUoUCJcUP%2bsmJjMXZg== This one for mouser is right. I completely forgot the XHP50 was a 5x5 led which is larger than the XP-g ones.


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## cincin (Jan 28, 2016)

mds82 said:


> DIWdiver is right about the board...  http://www.mouser.com/ProductDetail/Bergquist-Company/804936/?qs=jQRjkUoUCJcUP%2bsmJjMXZg== This one for mouser is right. I completely forgot the XHP50 was a 5x5 led which is larger than the XP-g ones.



Thanks for clarifying  I'm glad you both agree as this would've made the choice difficult.


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## cincin (Jan 28, 2016)

I have yet another question: switching the BuckBlock driver on and off.

Here's what the documentation (goo.gl/u5mXP0) says:

“Where a manual on/off control is desired, the potentiometer in Figure 14 may be replaced by a
pushbutton or toggle switch. The output current will be zero and the input current will drop to the
quiescent level when the switch is *closed*. Figures 16 and 17 show external dimming control combined
with on/off control. “

They also say: "When the dimming wires (purple/gray) are left unconnected, the A009 is designed to supply its rated
current to one or more LED junctions."






So if I get this right the dimming happens based on the voltage difference between the DIM and DIM GND pins. No voltage difference meaning OFF.

So in effect, the function of the POT is reversed, greater resistance = greater output.

and I cannot use a POT with built-in switch correct? Because the OFF position of the switching POT would cause the driver to deliver full power.

So to add a switch to the equation I need to do as in their diagram, put it in parallel with the POT.

The original scope setup has a switching POT and I'd really like to keep this original and not need an additional switch + a new hole for it. Are there POTs that have a separate switch circuit? Or combination POT and push-down switch or something like that that you guys know of?

Or can I rely on the fact that if the POT goes to 100% it will essentially turn off the driver? I'd still like a click notch to ensure it stays off... do they make POTs with click notches at 100%, or reverse switching POTs?

I realize this may be better asked on an electronics forum, but so far you guys know everything I need to know 

Thanks!


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## mds82 (Jan 28, 2016)

i cant answer all those questions, but when the grey/purple wire are connected then it will stop all current to the LED. if the grey/purple wire are not connected it will output the full current


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## cincin (Jan 28, 2016)

mds82 said:


> i cant answer all those questions, but when the grey/purple wire are connected then it will stop all current to the LED. if the grey/purple wire are not connected it will output the full current




Yep, I got that much figured out as well. I just need to find a way to put a switch/POT combo on this so the driver can be dimmed AND turned ON and OFF from the same knob.


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## cincin (Jan 28, 2016)

Also, the XHP50 has a forward voltage of 12v, but I'm putting it on a 6v star board, does that mean that the forward voltage will be 6v?

Just double checking I picked an appropriate battery pack...

I ask so many questions.... you guys have been amazing help! I'll make sure to post when the conversion is complete, I would've never been able to do any of this without your support.


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## FRITZHID (Jan 28, 2016)

cincin said:


> I have yet another question: switching the BuckBlock driver on and off.
> 
> Here's what the documentation (goo.gl/u5mXP0) says:
> 
> ...



As I can gather, connect switch across (series) with the POT and use them separately OR use a switched POT and connect the outside 2 pins of the POT in reverse so light will dim until switch activates rather than the other way around.


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## cincin (Jan 28, 2016)

FRITZHID said:


> As I can gather, connect switch across (series) with the POT and use them separately OR use a switched POT and connect the outside 2 pins of the POT in reverse so light will dim until switch activates rather than the other way around.



Hmmm wiring it backwards! Cool idea! But regardless of which way it's wired, isn't the OFF position of the switching POT going to cause FULL ON operation, since in the OFF position no current passes?

I don't understand how switching POTs wiring works clearly


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## FRITZHID (Jan 28, 2016)

Just need a POT with n.o./n.c. ability, that way you have either as an option.


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## cincin (Jan 28, 2016)

FRITZHID said:


> Just need a POT with n.o./n.c. ability, that way you have either as an option.



Excellent! Thanks.

I'm really starting to understand more and more about those bits and pieces, just as I realize this, my forum user rating now shows "Enlightened".

The forum knows.

So a double throw rotary switch POT will work for that. $10 instead of $3 but it'll work just like the original knob.

So the last question remaining before I order everything is:

the XHP50 has a forward voltage of 12v, but I'm putting it on a 6v starboard, does that make the effective forward voltage 6v or 12v?
Just confirming that I chose the right power pack.

Thanks again


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## DIWdiver (Jan 28, 2016)

The XH-P50 has two 6V sections. If you wire them in series, you get 12V. If you wire them in parallel, you get 6V. If you put it on an XM-L star, it will wire them in parallel, giving you 6V.

The driver will continue to draw several mA if you turn it off by shorting the dimming input to ground. This would drain your battery over a few months. This may or may not be a problem for you, but I thought I should point it out.

Fortunately, you can kill two birds with one stone by getting a regular switch/pot and wire the power input to the driver through the switch, instead of the dimming input.


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## FRITZHID (Jan 28, 2016)

Misread, corrected. Yes, he's right, always easy to switch the input. There may be some lag at startup but that shouldn't be an issue.


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## cincin (Jan 28, 2016)

DIWdiver said:


> The XH-P50 has two 6V sections. If you wire them in series, you get 12V. If you wire them in parallel, you get 6V. If you put it on an XM-L star, it will wire them in parallel, giving you 6V.
> 
> The driver will continue to draw several mA if you turn it off by shorting the dimming input to ground. This would drain your battery over a few months. This may or may not be a problem for you, but I thought I should point it out.
> 
> Fortunately, you can kill two birds with one stone by getting a regular switch/pot and wire the power input to the driver through the switch, instead of the dimming input.



So you're saying wire the power input to the driver through the switch pins of the POT, and wire the DIM and DIM GND through the variable resistance pins of the POT?

Wouldn't I need a POT capable of 12.5W on the switch circuit for that?
those appear hard to find in the 20K Ohm variety I need for the dimmer circuit.


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## FRITZHID (Jan 28, 2016)

cincin said:


> So you're saying wire the power input to the driver through the switch pins of the POT, and wire the DIM and DIM GND through the variable resistance pins of the POT?
> 
> YES, EXACTLY.
> 
> ...


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## cincin (Jan 28, 2016)

> _So you're saying wire the power input to the driver through the switch pins of the POT, and wire the DIM and DIM GND through the variable resistance pins of the POT?_
> 
> _YES, EXACTLY._
> 
> ...



I'm sorry if I'm being dense here, please bare with me. I understand that the POT resistance circuit can be low wattage, thanks to the driver DIM circuit. But the switch part of the POT also has a power rating. In the case of the POT I had chosen:

http://www.digikey.com/scripts/DkSearch/dksus.dll?Detail&itemSeq=188767905&uq=635896041920284070

The Datasheets say:

http://www.bourns.com/docs/Product-Datasheets/3310.pdf

"Switch Characteristics
...
Power Rating (Resistive Load) 100 mA @ 16 VDC"

Again, I don't know what I'm doing, but to me it sounds like I shouldn't try to put the full draw of the current going into the driver (12.5 watts I think?) through that switch.

Just trying to be safe 

If someone can kindly suggest the appropriate 20k ohm POT, or just confirm that it's safe to pass the power in through one of those tiny POT switches and I'll stop bothering you all.

Thanks!


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## cincin (Jan 31, 2017)

Greetings!

It's been a while, because the project got put on the back burner, but I just completed the conversion. Since I couldn't have done it without you guys I thought I'd let you all know that it was a full success! I'm a very happy camper.

In an effort to help the next person doing a scope conversion, I will leave some comments and feedback about the setup:

- The amount of light is perfect, any brighter would nearly be too much even for 100x darkfield observation.
- The minimum level of the driver with this POT is not all that low, and flickers just a tiny bit. Definitely low enough, but at 4x it's nice and bright, so a stronger LED might be too bright at minimum. Maybe a non-linear pot?
- The color rendition of these 90cri LED is fantastic compared to incandescent. Very white with brilliant colors!
- The system runs basically cold in my scope, so no interferences with the sample, or drift!
- Light coverage is very even in my scope, the 4 elements of the LED unit, or the size of the light source, don't seem to be a problem.
- The POT is a little bit light duty in my beefy german scope, a metal POT would've been a better choice. Might replace mine. The Off click is very faint on this one too.
- The wiring suggested above works very well with the Vin going though the switch of the POT, and the POT being wired in reverse to the driver so that it goes Off->min->max
- Reflowing a LED is pretty easy, and if you mess it up the first time you might be able to undo it all and start over without killing any parts... :laughing:
- No idea of battery life yet, the battery pack I got off eBay is a bit hard to understand... 3 LEDs and no apparent way of telling when it's charged or discharged.. lol. But I can take this scope out in the woods in a Pelican box for field observations! Fancy.

I was going to post photos but there's not much to look at, and half the pieces are fixed to the lid, and the other half to the inside, so I can only open it a bit without having to disconnect some elements. You can imagine what it looks like.

So for about $100 (in Canada) you can convert your microscope to high power high CRI rechargeable LED illumination with great success and little effort.

Cheers to all who helped!


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## mds82 (Feb 1, 2017)

Post a picture of what it looks like finally, i'm curious to see


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## DIWdiver (Feb 1, 2017)

Congrats on your success. Glad we could help.


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