Home Brew MTG Based MR16

Hi Candle Power Forum Folks,

I'm attempting to build an MTG based MR16 using the Nuventix MR16 cooler. Following the CREE reference design I've got myself an MTG star, Ledil reflector, and a National 3401 eval board. I would have liked to use the heatsink that the reference design called out but it seems like one off hobbyist types like myself can't purchase them.

I'm anxious to see the MTG in action and to see how well the Nuventix cooler works. The issue I'm having is that the national driver is set up to work off 12V AC and the Nuventix cooler is set to run of 3.3v DC. I'm not enough of an electrical engineer to come up with a plan to rectify the 12V AC source to supply the Nuventix cooler with 3.3V DC. Any advice that could be provided on this front would be greatly appreciated.

-Bill

The Nuventix Synjet MR16 Cooler runs off 4.75V to 5.25V (nominal 5V) and draws 360mA. The MTG Vf at 1100mA is 5.6V. You could design The LM3401 to output 1460mA and then wire the Cooler and Led in parallel on the output. You would have to add a small resistor inline with the Cooler to bring its supply voltage down to 5V. Start with a 5W, 2ohm resistor and then reduce the resistance until you get 5V across the cooler.

Other than that, I think the nuventix coolers are supposed to be run with specialty drivers that have specific outputs for them.

Hi AndersonEE,
Thanks for your reply. You're right the cooler takes 5V or 12V. I spaced out on thinking it was 3.3.

Today I drilled and tapped the heatsink, attached leads to the MTG starboard and mounted it with thermal paste to the heatsink. I decided to power the cooler with 5v constant voltage from a cell phone charger. I can hear the system working and feel airflow. Later on I will try to find a way to tap into 5V on the national board as you suggested.

The national board needs 12v AC. In the same manner I got a 12V AC charger. I had a difficult time determining the polarity on the AC supply. I figured that the striped wire on the left side was neutral and the right was hot. Here is the spec page on the national driver and eval board: http://www.national.com/rd/RDhtml/RD-188.html

When I hooked everything up the MTG lit up dimly and pulsed a bit in its light output. Any ideas on where I've gone wrong?

I hope I didn't do too many bone headed moves on this project/experiment. I'm pretty sure I haven't destroyed anything at least.

What 12V AC charger are you using? Are you sure it is rated for the amount of current you are trying to pull?
Can you post a picture of your setup?

Very interesting project. Where did you get the Cree MTG?

I got some starboards from cutter. I have one cut tape chip that I will try to reflow on to a starboard here pretty soon.

The AC power supply is good for 1.25A. I don't suppose that the national board was consuming so much current that the LED wasn't getting its fair share.

I will try to get some pics on soon.