10 Watt HID to LED Conversion

[Roko]

I have a 5 year old Greenforce light with a 10 Watt Welch Allyn Solarc HID bulb, the kind commonly used in 10 Watt dive lights from a few years back before Welch Allyn stopped making HID bulbs in the MR11 format.

The light is rather quite anemic compared to pretty much anything any of my dive buddies use, so I've decided to swap out the HID bulb for a Cree XM-L2 U2 LED bulb. I'm documenting the process on my blog ( GreenForce HID Upgrade | dive.roko.ca ), including very non-scientific tests of various collimators to see which gets the nicest beam. It's still a work in progress...

Although I'm converting a GreenForce HID, this should be applicable to any 10W HID can light using the Welch Allyn Solarc HID bulbs.


A busy photo showing the old HID components and new LED components (including the three different collimators I'm testing)

Edit: As a teaser, here is the performance upgrade I'm expecting with this swap (Photos taken with the camera in manual mode with the same settings and test setup (shining a the ceiling in a dark room)

5-year old 10W HID bulb:


Cree XM-L T6 with one of the collimators I'm testing:

 

[mddolson]

Roko,

Nice job. I took a look at your web page. You've made some good progress.
I've left you a couple of comments & would like to converse further.
I' have a 10 WA HID light I'd like to convert to LED. (just for drop resistance) & I have a new backplate project underway also.

Mike D

 

[Roko]

Thanks Mike!

I highly recommend this LED upgrade. It's blowing everyone's 10 watt HIDS out of the water. Even with a wider bream than a HID, it still works fantastic for signalling.

The only thing that's bugging me about it at this point is the driver, which I suspect is very inefficient. If I ever find the time, I'm planning on making a custom driver.

 

[mddolson]

Thanks Mike!

I highly recommend this LED upgrade. It's blowing everyone's 10 watt HIDS out of the water. Even with a wider bream than a HID, it still works fantastic for signalling.

The only thing that's bugging me about it at this point is the driver, which I suspect is very inefficient. If I ever find the time, I'm planning on making a custom driver.

If you do decide to build your own driver I suggest you want a flat 3.7 V DC & current at 850 mA
Dimming should be via PWM (pulse width modulation).

This will give you about 30,000 hrs life with out loss of output.

I wasn't surprized to see the blanking disk in the center of you lens (columator) The side light passing through the center is uncontrollable so it's blocked. Same technique used on head lights. The put the lamp behind a shield, & some bulbs have the end blackened to stop front glare.


Mike D

 

[Roko]

Hi Mike, I'm planning on designing the driver to drive the XM-L LED at the full 3000 mA (at which point it has a ~3.35v forward voltage), which is more or less what the cheap-o driver I use drives it at right now.

Even driving it at max current like that, the TM-21 L90 projection from Cree is over 10,000 hours of bulb life, which would equates to well over 10,000 dives -- LED life definitely won't be the limiting factor.

 

[mddolson]

Personally I would not drive the LED at more than 1500 mA.
Once the junction on the LEd exceed 140°C, there is a permanent reduction in the output.
What sort of temperature ar you seeing on the board next to the LED at 3 Amp?

Mike D

 

[Roko]

I don't have the means to accurately measure the temperature at the moment, so I'm not sure exactly how hot it's running. Fully assembled and underwater, I suspect it will be lower than it would be when measured in air.

From the datasheet, the thermal resistance of the XM-L to the solder junction is 2.5 C/W, so drawing about 3.35V*3A=10.05W leads to a temperature rise of about 25 degrees C at the solder junction, above whatever temperature the aluminum-substrate PCB is at. I'm not sure what the overall Rj-a of my heatsink design is, but The aluminum PCB and slug of aluminum I use to draw heat away from the junction don't seem to heat up too much in air (Based on non-scientific "to the touch" testing), and has good thermal routing to ambient, so I'm not overly concerned.

Since the goal of this upgrade was to upgrade my dying HID light for as cheap as possible, the use of this setup will probably be measured in the hundreds of hours or less over it's lifetime before I upgrade to a new canister light altogether (I'm not satisfied by the beam-width on this one, I would prefer a tighter beam). I'm not too concerned about reduction in the output below theoretical -- I think even with a reduced output at 3A, it will still be much brighter than a perfect output at 1.5A.

Either way, it blows my old 10W HID light out of the water.