Question on modify a KuangRen Macro Twin Lite KX-800 to an UV flash for UVIVF

[Pufferchung]

I have a KuangRen Macro Twin lite KX-800 that I bought for Macro photography. A couple months ago, out of curiosity, I decided to removed the two plastic front panels to see if I could modify the twin speedlite for UVIVF. The speedlite tube looks similar to Yongnuo YV560IV that I modified for UVIVF. So I placed two ZWB2 filters and surprised to discover those two small speedlites produce enough UV for UVIVF photography. I don't have any equipment to test how much UV the twin speedlite produced but still! What a nice surprise!

I really like how convenient to use the Macro twin flash for my field observations. I document UVIVF on wildflowers for INaturalist. I am thinking to change the LED emitter of focus assist light to an UV 365nm LED emitter. Is there anyone you would recommend who would modify my Macro twin flashlight?

Thank you!

 

Michelle

[Cadmium]

Well, I'm waiting, no idea here, but I am waiting on those who might.

[dabateman]

Not the best place to post this question.

Might have better eyes in the correct section.

 

I would suggest PM Ulf. He seems to be the Led master. But he might be busy with current projects.

[Cadmium]

Puffer, Don't worry, I think people will see it how it is for now. Someone has to know.

[Pufferchung]

Cadmium:

It’s ok! I am using my convoy C8+ UV flashlight as a focus light and converted UV YN560IV speedlite for field observations now. Since it’s winter, there’s not that many insects and flowers right now. The YN560IV is not perfect but still useable.

[ulf]

I think it might be difficult to exchange the LED to an efficient 365nm-version emitting enough intensity.

If you want a better focussing aid for UV, 365nm might be too short, as few autofocus lenses have a good transmission there.

Maybe a 380-385nm would work better, but then correction for focus shift will not adjust for 365nm, if the lens at all works there.

 

The 5R1 resistor tells me that there likely is not that much current flowing through the VIS-LED and we do not know what voltage that is available and how much current that could be delivered.

If you have a volt-meter you can measure the incoming voltage and polarity between the resistors right-topmost pole and the LED's pin to the right.

If you also measure the voltage over the resistor only you can calculate the current through the LED.

 

 

There are 365nm LEDs with the same casing as the one in the picture.

https://www.ebay.com...OkAAOSw~O1a5FSH

 

All those LEDs have a third metal connector at the bottom intended for heat transport.

If the circuit board have a matching pad under the LED it will be almost impossible to desolder with a soldering iron.

 

It might be that the circuit board is simple and without that pad as the focussing aid is on for a very short time and thus not have time to overheat the LED.

Then it would be easy to exchange the LED.

If I knew the LED were just attached with the pins I would cut the LED body away first with a fine wire cutter and the de-solder the pins separately, before soldering on the new LED.

 

The polarity is important for the LED.

If you look at the pins just by the LED's body the extending width is different. That is a polarity indicator.

 

You might exchange the entire PCB with a new one like something like this:

https://www.ebay.com...YMAAOSwARZXoFBS

Then you must add a suitable current limiting resistor in series with the LED.

[Pufferchung]

Hi UlfW:

 

Thank you very much for such detailed explanation, all the information that you provided are super helpful. The process seems to be too complicated for me, but could be done by a professional electronics technician. I knew some EE students here in the university, will ask them see if anyone could modify the focus light for me.

Once again, thank you so much!

 

Michelle

[ulf]

I'm happy to help.

 

Don't hesitate to ask again if new questions comes up after you get help beginning the modification.

It is always wise to do these things stepwise, first collecting more information, before deciding the next step,

I can only guess from what i see in the pictures and draw conclusions of likely designs used.

[ulf]

If the modification is done by replacing the entire board as I say in the end of my first post, the new resistor could possibly be replaced with a constant current driver.

The maybe one of these could be used:

https://www.digikey.com/en/products/filter/pmic-led-drivers/745PZQDaIAzAJwBsNArCALqEAOALlCAMrsBOASwB2AcxABfQmAAMVGIhApIGHAWJlKFCmCpVmbTpB79hYyeDl7oitFjyESkctP0gOXXoNETCAWkbWSir26k4gAEyu7kYS4uJAA

The EE students might help you decide if that is OK.

[Pufferchung]

If the modification is done by replacing the entire board as I say in the end of my first post, the new resistor could possibly be replaced with a constant current driver.

The maybe one of these could be used:

https://www.digikey.com/en/products/filter/pmic-led-drivers/745PZQDaIAzAJwBsNArCALqEAOALlCAMrsBOASwB2AcxABfQmAAMVGIhApIGHAWJlKFCmCpVmbTpB79hYyeDl7oitFjyESkctP0gOXXoNETCAWkbWSir26k4gAEyu7kYS4uJAA

The EE students might help you decide if that is OK.

Hi UIf:

 

I clicked on the link but the product is no longer available. Would you please send me the link again? Thank you.

My daughter is going to change the LED emitter for me. She built custom made mechanical "light up" keyboards for gamers, so she knows how to soldering and desoldering stuffs. She said she is going to try to change it and her EE friends are going to help her.

 

Have a lovely weekend!

 

Michelle