Tungsten to LED Microscope conversion

Have questions about the equipment used for macro- or micro- photography? Post those questions in this forum.

Moderators: rjlittlefield, ChrisR, Chris S., Pau

DavyC
Posts: 109
Joined: Sat Sep 22, 2018 1:53 pm
Location: UK

Tungsten to LED Microscope conversion

Post by DavyC »

With an older type Nikon Eclipse E200 on the way. 'Older' being illumination via a 6v 20w Halogen bulb.
The more recent version has an LED source.

Looking twice at the price of this 'LED swap out upgrade' there was a sticker shock of $500!
There must be a total of $30 in components!
Now I recognise a 'Get rich quick' scheme when I see it.

OK, it's different Scopes for different folks, but has anyone had a go at rolling their own LED solution?

PeteM
Posts: 178
Joined: Sat Jan 05, 2019 12:06 am
Location: West Coast, USA

Re: Tungsten to LED Microscope conversion

Post by PeteM »

A LED conversion shouldn't be very difficult. However, I'd try the 20 watt halogen source before deciding it needs an upgrade. It should do fine for brightfield, darkfield, and phase contrast.

If you decide you want a brighter or cooler source, the main thing is to place a LED die of about the same size and at the same location as the filament. You'd want a 3-5 watt LED to be sure of something as bright or brighter -- and those did start to get expensive in single die versions.

DavyC
Posts: 109
Joined: Sat Sep 22, 2018 1:53 pm
Location: UK

Re: Tungsten to LED Microscope conversion

Post by DavyC »

A LED conversion shouldn't be very difficult
Thanks Pete,
I have ordered a new halogen bulb. Light output starts to gradually fade early on with these bulb types.

Bulb colour temp is 3350k, which is a bit too warm I think.
460 lumens of light output, so I would think you are right about the LED equivalent wattage.

If I can fashion something workable, then I can justify treating myself to a new objective!

It's only fair.

chris_ma
Posts: 570
Joined: Fri Mar 22, 2019 2:23 pm
Location: Germany

Re: Tungsten to LED Microscope conversion

Post by chris_ma »

DavyC wrote:
Wed Oct 06, 2021 12:57 am
Bulb colour temp is 3350k, which is a bit too warm I think.
it's a bit higher temperature then a standard halogen (3200K) which means it will burn out faster, but also has a better color balance (more blue photons) and higher efficiency.

so other then replacement costs, it's actually preferable to a standard halogen.
chris

DavyC
Posts: 109
Joined: Sat Sep 22, 2018 1:53 pm
Location: UK

Re: Tungsten to LED Microscope conversion

Post by DavyC »

it's a bit higher temperature then a standard halogen (3200K)
Chris,
I have ordered a range of 4000k - 5000k leds to test and try to give a more neutral tint. Not quite daylight.
The point I was making about the 3350k Halogen bulb is that it is on the warm side.
A case of in it's day that was generally as good as it got.
People were conditioned to this as a norm. Even Ikea and the like started producing LED bulbs to replicate
warm homely bulbs of old. They still do make nasty 2700k lights.

Pau
Site Admin
Posts: 6053
Joined: Wed Jan 20, 2010 8:57 am
Location: Valencia, Spain

Re: Tungsten to LED Microscope conversion

Post by Pau »

Typically a blue filter (usually provided with most microscopes) is enough to have nice well balanced illumination with halogen or other incandescent lamps for vision.
With a digital camera a custom white balance is to be recommended in all cases.

Halogen usually does not flicker and has good continuous regulation but colour temperature changes with the power setting and produces more heat. When very low powered the light is too reddish and the bulb life can be shorter, so in case of too bright illumination neutral density filters are very useful.

LEDs are very variated. I would recommend 4000-5000K models like you ordered and high CRI if available.
Often they are more problematic to be regulated and if you use PWM to dim them look for high speed ones to avoid flickering. If you use a pot dimmer model you could have poor regulation at low power, so, again, ND filters are very convenient.
Of course I concur with Pete's advice.
Pau

DavyC
Posts: 109
Joined: Sat Sep 22, 2018 1:53 pm
Location: UK

Re: Tungsten to LED Microscope conversion

Post by DavyC »

LEDs are very variated
Good points Pau.
LED quality can vary widely especially bargain bin lots from the far east.
They are also prone to fade over time. I agree with using high CRI units.
I like to keep some Lee/Rosco gels to balance out speedlights matching other light sources.

I haven't much experience with pwm, but I may get round to that, if I can't work out
a simpler variable current route.

DavyC
Posts: 109
Joined: Sat Sep 22, 2018 1:53 pm
Location: UK

Re: Tungsten to LED Microscope conversion

Post by DavyC »

Thanks to all who gave their thoughts and help.

Well today a man showed up with a Nikon in a box.
I had bought this with trepidation.
I had scoured the photos and even got the seller to take some more.
It was a 'Spares or Repair' Scope. I wanted any visual clues as to condition.
A good sign I thought. A sticker from a tester label.
'Suspect a broken bulb', All 'mechanisms work'.

So, i opened up the inners for inspection. True to the label, the bulb was indeed blown.
A new bulb inserted and covers back on. There was light!

So I have to say I was pleased. Still need to do a bit of a service, by way of a clean up and test.
One thing I did notice was the blue filter in the Condenser unit. I had taken for granted that this was just an add on aftermarket accessory. 'Doh!
Still, I do want to do the LED conversion, so took some measurements to be able to get that underway.

I took a chance, so by way of a money saving reward, I ordered an accessory.
I mean, that's fair, isn't it?
Attachments
Nikon-10x.jpg

ModelZ
Posts: 71
Joined: Sun Nov 01, 2020 4:34 am
Location: Northern Europe

Re: Tungsten to LED Microscope conversion

Post by ModelZ »

Excellent advice given above. Perhaps I may chime in a bit from my experience.
Been doing several of these conversions now, for Reichert, PZO, Zeiss and Lomo units. The key to get the ball rolling for me was the word BuckBlock. Easy to make the unit using those circuits and a potentiometer. Sometimes one needs NDs to control lower end as Pau noted above. Leds are of varying quality, but easily upgradeable if you first err to a weak one.
Just recently converted a Zeiss 12V 100W halogen unit to led. I didn't have a big enough power source and it didn't make sense to buy one for that alone. Also these high power bulbs are fairly expensive and won't last that long. So it was an easy decision to convert. Now I'm using it happily with a 10W neutral whilte led.
Learned something interesting along the way. The halogen leaks a fair bit of UV whereas the led doesn't. In some samples you see slight UV fluorescesce glow with the halogen that you don't get with the led. Halogen has a pretty much monotone emission spectrum tapering off somewhat below 400nm, whereas led emission is controlled with phosphorus that only yields in the visible. Safer for your eyes (although there still is some questions about the deep blue on your eyes) but I thought it was interesting to know that with halogen you really can catch something more. Of course it could just as well confuse in trying to interpret the image.

DavyC
Posts: 109
Joined: Sat Sep 22, 2018 1:53 pm
Location: UK

Re: Tungsten to LED Microscope conversion

Post by DavyC »

Excellent advice given above
Thanks for that ModelZ.
Today I ordered up some discrete components as well as a pwm controller.
Will use the existing lighting transformer to provide the power.
A bit of a test and tweak with components.
For fun, I ordered more stuff than I need.
The LEDs presentartion can be a bit 'flat', but it calls for a better quality high cri rating to help.
The halogen as you say provide something a bit different.

Scarodactyl
Posts: 1617
Joined: Sat Apr 14, 2018 10:26 am

Re: Tungsten to LED Microscope conversion

Post by Scarodactyl »

100w halogen bulbs are not very expensive and very easy to source. Switching to LED really isn't a savings from that perspective, just since it's a fairly negligible expense. Maybe if you were running it 24/7 in a lab setting it would be more of a concern. That's not to say LEDs don't have their advantages of course.

DavyC
Posts: 109
Joined: Sat Sep 22, 2018 1:53 pm
Location: UK

Re: Tungsten to LED Microscope conversion

Post by DavyC »

Maybe if you were running it 24/7 in a lab setting it would be more of a concern
The future for halogen bulbs is looking dim. Already banned in some countries.

It's the cumulative effects of all those energy hogging bulbs burning.
Messing up the thermostat on polar bears outdoor fridges.

After a shaky start, LED lighting has sounded the death knell for Halogen bulbs.

DavyC
Posts: 109
Joined: Sat Sep 22, 2018 1:53 pm
Location: UK

Re: Tungsten to LED Microscope conversion

Post by DavyC »

Update.
So far, so good!
Changing over to a LED light source, I needed to lose the old Nikon lighting circuit.
I wanted to increase efficiency, provide greater protection and add extra smoothing to the power supply.
So I made and installed a new PCB, fitting additional upgraded components.

With reduced current consumption and increased efficiency, I retained the Blue condenser filter, as even with the light transmission loss,
it did improve colour rendering to approximate daylight.

A PWM controller was added to give greater control.
It was a tight fit, getting all the extra bits and pieces fitted in between the lattice of the casing.

With the led fitted in the original bulb location, all components installed and things back in place,
switch on and have to say I am pleased with the results.
Attachments
Nikon-new-layout.jpg
Nikon-original.jpg

Post Reply Previous topicNext topic