420 Magazine Background

Need help with DIY COB light

Xerox17

New Member
Using 18 x bridgelux bxre-40e2000-c-23 with 3 meanwell Hlg-240h-c1050b drivers. Six cobs in series per driver. Used 4 15 inch x 13inch diamond plate aluminum plates with 1.5x1.5 1/8in angle to connect the 4 plates to make a 3ftx3ft square. I have 4 cobs per plate with 2 on the center cross bar so I imagine I have more than enough aluminum to act as a heat sink. I am using thermal tape to stick the cobs to the aluminum and soldering 18ga solid stranded wire directly on to the solder pads. Problem I am having is that no matter how well I solder them or how hot of a soldering iron I am using once I power them on it last between 5-15 seconds before I get some smoke and my wires will desolder themselves and pop off. I've been soldering for 10 years and never had anything like this happen with any of my solder joints. It cools pretty instantly once it loses power so I can't get an accurate temp reading.
 

fanleaf

Well-Known Member
There has to be a short somewhere. Theres not much power going through the wire under normal operation so I cant see a decent solder joint hitting 400 degrees in 10 seconds. Just go through and be sure you are + to - or - to + all the way down the series. Double check all chips are in chip holders the correct direction. Which holders are you using? I've never even had 20 awg get over room temperature even at much higher power levels than you are running. Somethings not wired correctly.
 

Xerox17

New Member
No short anywhere I checked before the first time I powered everything up, before mounting I made sure none of the solder pads shorted to the aluminum backing on every single cob, after mounting and wiring I checked for shorts and short to the heat sink and have none. But since I posted this I hooked a DC variable psu up to the dimmer leads and dropped it down to 1v. The driver dimmed all the way was putting out .177a and 100 and something volts. Nothing popped this time but the cobs are getting hot even under sick low current. I guess they aren't getting good thermal transfer because the aluminum isn't even getting warm.
 

Xerox17

New Member
Also I'm not using any chip holders I haven't been able to find any for these cobs that's why I opted for the thermal tape to keep them stuck on
 

fanleaf

Well-Known Member
Your best bet on the dimmer wires is to solder on a 100k ohm potentiometer instead of adding voltage to the dimmer. That way you can turn up and down as you please. Yeah, at only 17 watts I'm shocked the chips even got warm lol. That's only 3 watts per chip.
 

Xerox17

New Member
Sweet I'll have to look into those and I'm going to resurfance the aluminum tonight starting with 220 grit all the way to 1200 grit maybe use some buffing and polishing compound afterwards as well
 

Xerox17

New Member
How do I check the price from bjb all I see is a button to request a sample, do I need an account first or do they have a supplier I have to look at?
 

Xerox17

New Member
I can't seem to find anything miswired, 6 cobs per driver all in series checking with my dmm nothing has continuity that shouldn't and nothing has continuity to the frame. I removed all of the cobs tonight and resurfaced the aluminum down to 1000 grit. I'll be remounting all of the cobs and rewiring in a little bit.
 

Xerox17

New Member
Some of the reviews on rapid say to make sure you run these cool because they run super hot. Check out that site and see if any of their docs provide some additional insight.
Where did you find these on rapid? The only bridgelux I find on there are Vero 29's
 

Xerox17

New Member
I think those might be for the gen 7 and I'm pretty sure these cobs are gen 6 that I have from other things I've seen the gen 7 holders won't work with the gen 6 cobs
 
Top Bottom