SSC LED polarity help

I am going to mod the Romisen G2 light with an SSC LED and the 1-mode hack of the DX 20-mode driver, but I do not know which lead of the SSC LED (I got the bare LED) is positive, and which is negative. Can someone please help?

This is the picture of the LED:

The cathode (negative) tab is on the left in your photo, next to the notched short tab.

The left side (the side with the U notch) is negative. The other side and the bottom are positive. So you may need to isolate the bottom before installing.

ecll said:

The left side (the side with the U notch) is negative. The other side and the bottom are positive. So you may need to isolate the bottom before installing.

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Thanks for your help.

If I am going to mount it directly onto the heatsink, how can I electrically isolate the bottom?

For the future:

You can test the polarity of any Led with one CR123 cell or 2xAA cells (max.3 Volts)

BTW:

a very thin layer AA-epoxy can be used for isolating the bottom.

Good luck and best regards

____
Tom

Why didn't you simply replace the whole star with the led on it? THen the positive base of the Seoul doesn't matter. Or is the star too big?

meuge said:

I am going to mod the Romisen G2 light with an SSC LED and the 1-mode hack of the DX 20-mode driver

Click to expand...

I'm curious about this, I hadn't seen any threads on this, and tried to find them, can you point these out, in regards to the 1-mode hack?

The side that has the tab with the center cut out of it is the Cathode (-) side, the other side is the Anode, you may want to see if you can find a spare Star PCB for it (or if it is an emitter swap make sure you have some sort of thermal compound because seouls are sensitive to heat)

wildstar87 said:

I'm curious about this, I hadn't seen any threads on this, and tried to find them, can you point these out, in regards to the 1-mode hack?

Click to expand...

It's very simple. Just solder the negative wire to the copper outer ring of the driver board, as opposed to the chip it comes soldered to. This makes the driver a 1-mode.

Btw, a review of my mod is up here:
https://www.candlepowerforums.com/threads/185106

Lightingguy321 said:

The side that has the tab with the center cut out of it is the Cathode (-) side, the other side is the Anode, you may want to see if you can find a spare Star PCB for it (or if it is an emitter swap make sure you have some sort of thermal compound because seouls are sensitive to heat)

Click to expand...

I mounted it directly onto the heatsink with home-made thermal adhesive (cheap 2-part epoxy + Arctic Silver 5 thermal paste).

AS5 is electrically conductive... however mixed with generic 2 part epoxy I'm not sure how it will react, curious did you check for electrical isolation after the epoxy/AS5 hardened?

FWIW in relation to the original polarity question, the quick and dirty method (as laready hinted to previously) is to locate the anode using the SSC emitter's base as a starting point with a continuity meter

M@elstrom said:

AS5 is electrically conductive... however mixed with generic 2 part epoxy I'm not sure how it will react, curious did you check for electrical isolation after the epoxy/AS5 hardened?

Click to expand...

AS5 is more capacitive than conductive. Put some voltage across a blob of AS5 and see how much current you can get through. It probably won't be much at all, especially at low voltages.

I did check for shorts after applying the mix, and measured infinite (>2M ohms on my meter) resistance. I figure that's good enough for me.

P.S. thanks for the second polarity tip - but when I first posted, I didn't know that the base was the anode.

i know its late but just wanna share

Long John said:

For the future:

You can test the polarity of any Led with one CR123 cell or 2xAA cells (max.3 Volts)

Click to expand...

You can, but with Seouls, there's an inbuilt static-protection diode. It's a Zener, which means that with reverse voltages above ~0.6V, a lot of current can flow.
I didn't realise the diode was there until I checked the reverse-voltage current draw of one of my caving lamps. With the Luxeon-based units it was insignificant, but with SSCs attached to identical driving electronics, it was a couple of amps, being somewhat limited by the path through the electronics.

From playing around, direct application of a 3xNiMH pack to a Seoul with reverse connection seems to blow the protection diode open about half the time, but turns it into a 2-way short circuit the other half of the time, making the LED useless.