Cheap 365nm LEDs from eBay - spectral measurement

[Avalon]

You ordered 365nm LED's from Ebay? UV LED's which appear whitish to eyes I bought 365-370nm from this seller: https://www.ebay.com/itm/1-10-20-50-100pcs-3W-High-Power-UV-ultraviolet-365nm-370nm-LED-Lamp-Light/261971848310?hash=item3cfebd2c76:m:mu0SICThgK8KGynhv-5ZSMA:rk:1:pf:0&var=560780652090

[JMC]

You ordered 365nm LED's from Ebay? UV LED's which appear whitish to eyes I bought 365-370nm from this seller: https://www.ebay.com...ar=560780652090

These were the ones I bought (in theory I ordered the 362-265nm ones); https://www.ebay.co.uk/itm/High-Power-3W-UV-Ultraviolet-365nm-385-395nm-400nm-425nm-LED-Bulb-Chip-20mm-Base/122504455510?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649

[dabateman]

Jonathan,

I think you got lucky with different profile. Now just buy 8 340nm Leds. And mix them into 3 blocks. You will then have a full range UV light. 340, 365, 385 (possibly) would be a nice light.

I would hammer the back side of the mould gently to create your plains to mount the LEDs. Kind of like a metal drum.

[JMC]

Got the spectrometer out. And of course the new LEDs aren't 365nm ones are they, they are 385nm ones.

 

The original ones have a blue/white hue in the visible spectra, and the new ones more a purple hue. I presume when I ordered 365nm ones, they just sent the wrong ones.

 

Well, looks like a desoldering and resoldering job is in order.

 

David, yes some 340nm ones will now make a nice mix.

[Cadmium]

Jonathan, I like it. Anyone ever seen the Nichia LED's WITH drivers? The LED's them selves cost about $10, but have to have the drivers too.

I don't think Nichia has a 340nm LED, as far as I know, but they do have a mix of 365nm...380nm...and up I think.

If you could find some actual 340nm LED's, would be nice to mix up maybe 3 different types and make them adjustable even? Maybe too fancy...?

I like the reflector too. You can always put a little fan on it if needed.

I like your power supply.

 

[Cadmium]

Jonathan, What power supply is that you are using there?

[JMC]

Thanks Steve. Yes I'd like to make each bank of different wavelengths independently adjustable at some point. I spent a few minutes last night desoldering and resoldering to spread the different ones out better.

 

Here's the strange thing though. I bought 2 batches of 10, both batches supposedly 365nm. I blew up one 365nm when I tested it to destruction a while back. Given then new batch seems to be 385nm ones, I assumed I should have 9x365nm and and 10x385nm. I actually have 12x365nm and 7x385nm. It looks like they have pretty rubbish quality control and that it was just a bit of a mix of wavelengths.

 

I've found a UK vendor for Seoul Viosys LEDs and there is a 340nm in their range. However it does not come attached to one of the small star shaped PCB boards. So I need to have a word with them and see if they can either supply them like that, or recommend someone who can mount them for me so I can use them.

 

The powersupply is a Manson EP-603. Quite an old one now, but nice and compact.

[ulf]

I've found a UK vendor for Seoul Viosys LEDs and there is a 340nm in their range. However it does not come attached to one of the small star shaped PCB boards. So I need to have a word with them and see if they can either supply them like that, or recommend someone who can mount them for me so I can use them.

Jonathan, can you please share information about the vendor and LED type? Maybe a datasheet?

[JMC]

Jonathan, can you please share information about the vendor and LED type? Maybe a datasheet?

Sure, the company is AP Technolgies; https://www.aptechnologies.co.uk/LEDs/UV

 

The one I had in mind was CUD4AF1B 6.3mm 60mW. The datasheet is available straight from the webpage above. I should say I haven't spoken with them at all yet about prices or suitability.

[JMC]

I resoldered the LEDs last night, to spread them out more evenly. Been to the shops this morning and picked up some flowers for my lovely wife, and claimed one of them for imaging. First a standard colour photo so you can see what the flower looks like in normal light.

 

And with UV LED ringlight, using my UV converted d810 and UV Nikkor, f22, ISO1250 and 25s exposure. Whitebalanced in Darktable. Contrast boosted slightly and curves tweaked in Photoshop but no further colour changes. Resolution dropped for sharing.

 

Try and ignore the background - I just put something there to block out what was behind, and ideally I'd want something darker. The Landrover log book had to make do.

[ulf]

Sure, the company is AP Technolgies; https://www.aptechno...s.co.uk/LEDs/UV

 

The one I had in mind was CUD4AF1B 6.3mm 60mW. The datasheet is available straight from the webpage above. I should say I haven't spoken with them at all yet about prices or suitability.

 

Those LED-cases need a proper reflow soldering machine for a correct soldering. It is nothing you can do in the kitchen. :)

I bet they carry a healthy price-tag too!!

 

The case-type of your cheap LEDs mounted on the star-shaped metal carrier-PCBs might be easier to handle.

[dabateman]

Jonathan,

60mW will look like a tinny dot next to your 3W others. I don't think it would be worth it.

Better to save up for these:

 

https://www.ebay.com/itm/High-Power-3W-UVA-340nm-Led-Chips-Deep-UV-Led-Emitter-Diodes-Radiant-flux-55mW/202120730112?var=&hash=item2f0f559600

[JMC]

Those LED-cases need a proper reflow soldering machine for a correct soldering. It is nothing you can do in the kitchen. :)

I bet they carry a healthy price-tag too!!

 

The case-type of your cheap LEDs mounted on the star-shaped metal carrier-PCBs might be easier to handle.

Hi Ulf, Funnily enough I have just been on the phone with AP about these. Yes, on the website they are unmounted, but apparently they can also supply them mounted on star mounts (depending on number needed). I have asked them for a quote for 20 of them mounted.

[JMC]

Jonathan,

60mW will look like a tinny dot next to your 3W others. I don't think it would be worth it.

Better to save up for these:

 

https://www.ebay.com...=item2f0f559600

David, even those in your link are advertised as a radiant flux of 55mW. The ones at AP are advertised as an output of 60mW. The images in the eBay link are for the same ones I am looking at (the code number CUD4AF1B is the same for the ones from Seoul Viosys). It'll be interesting to see what the quote om AP comes back as now.

 

The eventual aim would be to have the different wavelengths individually controllable, so I can turn down the longer wavelength ones.

[ulf]

 

Try and ignore the background - I just put something there to block out what was behind, and ideally I'd want something darker. The Landrover log book had to make do.

 

This looks really promising, but I think it would be good if the individual LEDs sat closer together. It might be a risk of the same multicolour-effect as in the background for some motives.

 

I guess your focus is to add 340nm LEDS.

For some filtering on the camera it might be interesting to add 395nm-LEDs too/instead.

There is much 395nm light too in normal sunlight.

[JMC]

David, even those in your link are advertised as a radiant flux of 55mW. The ones at AP are advertised as an output of 60mW. The images in the eBay link are for the same ones I am looking at (the code number CUD4AF1B is the same for the ones from Seoul Viosys). It'll be interesting to see what the quote om AP comes back as now.

 

The eventual aim would be to have the different wavelengths individually controllable, so I can turn down the longer wavelength ones.

Well, I got the quote back. They are cheaper than the eBay ones, however there is a minimum order, and it's way more than I need (minimum order quantity is 100, for the Seoul Viosys ones, and I had planned on using 16 on my ring light). So does anyone need any 340nm LEDs to help make the order viable? They would be 25GBP each plus delivery, mounted on the 20mm star mount PCB boards.

[ulf]

Well, I got the quote back. They are cheaper than the eBay ones, however there is a minimum order, and it's way more than I need (minimum order quantity is 100, for the Seoul Viosys ones, and I had planned on using 16 on my ring light). So does anyone need any 340nm LEDs to help make the order viable? They would be 25GBP each plus delivery, mounted on the 20mm star mount PCB boards.

When spending that much money it will be a very good idea to do a proper thermally correct design with good heatsinks.

 

Almost all power you feed into the LEDs will be converted into heat. Heat is the LEDs enemy. It will kill them if it gets too hot.

 

If you run them at nominal current, 0.5A they will dissipate more than 2W each making them very hot after a while.

A savarin-mould will not be enough for cooling, even if you flatten the mounting surface.

Combined with two other LED types, times 16 you have to get rid of close to 100W.

Even running at half power will give rather hot LEDs.

 

Compare to how the CPUs of stationary computers are cooled with heatsinks, heatpipes and fans.

They also are using constant thermal monitoring to protect them and are reducing the speed and power when things get too hot.

A CPU can generate around 100W and would quickly die without cooling.

[JMC]

Been thinking about that Ulf. If I do go ahead, I'd planned on getting something made to mount them too, to give more cooling. The savarin tin was fine for proof of concept, but as you say doesn't give enough cooling for anything more than that.