Gryloc
Enlightened
First off, I am working on a LED headlight replacement for my friends truck. I cover the project here:
https://www.candlepowerforums.com/threads/117661
I just got the LEDs today (36 TWOM K2's) along withg the optics. I could not resist getting a mock up ready for just one headlight. I have 18 of the K2's hooked up in 6 parallel banks of 3 series LEDs. This would work well. I was impatient and I was carefully driving the whole cluster with a little battery pack to see how it would light up. Everything looked awesome, untill a couple banks of LEDs turned off! Eeek!
I just discovered that the slugs on the bottom is very well connected to the negative leads! I never had problems making small clusters with LuxI's and LuxIII's using the same aluminum heatsink. I can hook up a continuity tester (built into my multimeter) to the slug and negative and it will beep at me for a K2, and not the older LED's (which I already knew about and dismissed a while back). I didnt know the K2's were built that much differently.
I hooked the whole cluster to the battery pack (two old standard 6V lantern batteries) and I made sure the current didnt go up too high (I measured current using the multimeter). It should run at 12.0V to 12.7V @9A max (1.5A x 6). It read about 2.5A or so with this pack.
I wanted to try the 9A a little to get these things going at full brightness. I used a lead acid jumper battery pack (for jump starting your car, of course). It was a small pack inside not rated for a whole lot of current. With this pack configuration, I got the whole cluster running at 7.3A (1.22A per LED bank) and the light was killer!
I was checking things out making sure the LED's made good thermal contact. I used thermal compound temporarily on an aluminum heatsink and I held them down with some strong tape. I have done things in the past this way with no problem. I wanted to save the two-part thermal epoxy for the nice copper heatsinks I need to build yet (waiting for the copper in the mail yet). None of the LED's really got hot. They were cool and I felt the giant heatsink warm up a little. All light was bright and uniform.
Anyway, when I had the LED's hooked to the lead acid battery (not fully charged), I had one LED stop working, turning off one bank. I freaked out a bit, but I found the issue with the one LED and the other two in series were fine. I had a spare of a slightly different tint K2 and I replaced that. It lit with no problem again. Bright! I have been getting pictures of the killer cluster and I decided to take it outside. It has no optics yet and it lights all the trees up outside for 50 or more feet. It lit up a flood with the same intensity all around as the beam of my 4XLuxIII 2DMAG mod with the 4 SO20 reflectors (really tight beam when untrimmed and used with joker Luxeon LED's)!!! Holy crap!
Here is some pics when indoors (my messy room). Here is a comparison of the ambient light (the Quad LuxeonIII flashlight shining up at the ceiling and my monitor) and with the K2 headlight cluster on a 7.3A. I had the same speed and amperature setting on my camera, so here:
As I was saying, I was outdoors and that is when the nail-biting crap happened. I saw after having it lit for about 10 seconds that another bank went out as another got dimmer! I quickly cut the power. The LEDs were still not hot or anything. I am left with a dead K2 in one bank with the others working fine and another bank with a dimm K2 with the others fine. The dim one was visibly damaged when you light it very dim. Part of the die doesnt light. Here is a picture of the cluster lit at a lesser intensity. You can see the problems clearly:
Okay, this is where I need help. How can I hook these up so this doesnt happen? Here is a diagram of how each light is wired:
I found when hooking the negative from a 6V battery pack to the negative of the cluster, then touch the positive of the battery pack to the alumunum heatsink, a certain few LEDs light up dimly. I believe that is a real problem when hooking the full voltage to the LED's for use in the car. Here is a small picture of how the few LEDs that lit up:
Notice how just the one LED at the end of each bank (the last one that is hooked to the main negative) are lit. The one labeled "1" was the one that was first replaced. LED "2" is currently not working but the others in the bank are.
How can I successfully isolate each LED (if I need to do this) while still providing good thermal contact? Would a thin sheet of anodized aluminim work? What about thinly painting a small spot underneath the slug of each LED? Would a thin sheet of mica work to isolate the LEDs? Hmmm.
Any help here would be appreciated. I am lost and this is holding me and the project back. Is there something I am missing? Thanks all. This is why I love CPF forums!
-Tony
https://www.candlepowerforums.com/threads/117661
I just got the LEDs today (36 TWOM K2's) along withg the optics. I could not resist getting a mock up ready for just one headlight. I have 18 of the K2's hooked up in 6 parallel banks of 3 series LEDs. This would work well. I was impatient and I was carefully driving the whole cluster with a little battery pack to see how it would light up. Everything looked awesome, untill a couple banks of LEDs turned off! Eeek!
I just discovered that the slugs on the bottom is very well connected to the negative leads! I never had problems making small clusters with LuxI's and LuxIII's using the same aluminum heatsink. I can hook up a continuity tester (built into my multimeter) to the slug and negative and it will beep at me for a K2, and not the older LED's (which I already knew about and dismissed a while back). I didnt know the K2's were built that much differently.
I hooked the whole cluster to the battery pack (two old standard 6V lantern batteries) and I made sure the current didnt go up too high (I measured current using the multimeter). It should run at 12.0V to 12.7V @9A max (1.5A x 6). It read about 2.5A or so with this pack.
I wanted to try the 9A a little to get these things going at full brightness. I used a lead acid jumper battery pack (for jump starting your car, of course). It was a small pack inside not rated for a whole lot of current. With this pack configuration, I got the whole cluster running at 7.3A (1.22A per LED bank) and the light was killer!
I was checking things out making sure the LED's made good thermal contact. I used thermal compound temporarily on an aluminum heatsink and I held them down with some strong tape. I have done things in the past this way with no problem. I wanted to save the two-part thermal epoxy for the nice copper heatsinks I need to build yet (waiting for the copper in the mail yet). None of the LED's really got hot. They were cool and I felt the giant heatsink warm up a little. All light was bright and uniform.
Anyway, when I had the LED's hooked to the lead acid battery (not fully charged), I had one LED stop working, turning off one bank. I freaked out a bit, but I found the issue with the one LED and the other two in series were fine. I had a spare of a slightly different tint K2 and I replaced that. It lit with no problem again. Bright! I have been getting pictures of the killer cluster and I decided to take it outside. It has no optics yet and it lights all the trees up outside for 50 or more feet. It lit up a flood with the same intensity all around as the beam of my 4XLuxIII 2DMAG mod with the 4 SO20 reflectors (really tight beam when untrimmed and used with joker Luxeon LED's)!!! Holy crap!
Here is some pics when indoors (my messy room). Here is a comparison of the ambient light (the Quad LuxeonIII flashlight shining up at the ceiling and my monitor) and with the K2 headlight cluster on a 7.3A. I had the same speed and amperature setting on my camera, so here:
As I was saying, I was outdoors and that is when the nail-biting crap happened. I saw after having it lit for about 10 seconds that another bank went out as another got dimmer! I quickly cut the power. The LEDs were still not hot or anything. I am left with a dead K2 in one bank with the others working fine and another bank with a dimm K2 with the others fine. The dim one was visibly damaged when you light it very dim. Part of the die doesnt light. Here is a picture of the cluster lit at a lesser intensity. You can see the problems clearly:
Okay, this is where I need help. How can I hook these up so this doesnt happen? Here is a diagram of how each light is wired:
I found when hooking the negative from a 6V battery pack to the negative of the cluster, then touch the positive of the battery pack to the alumunum heatsink, a certain few LEDs light up dimly. I believe that is a real problem when hooking the full voltage to the LED's for use in the car. Here is a small picture of how the few LEDs that lit up:
Notice how just the one LED at the end of each bank (the last one that is hooked to the main negative) are lit. The one labeled "1" was the one that was first replaced. LED "2" is currently not working but the others in the bank are.
How can I successfully isolate each LED (if I need to do this) while still providing good thermal contact? Would a thin sheet of anodized aluminim work? What about thinly painting a small spot underneath the slug of each LED? Would a thin sheet of mica work to isolate the LEDs? Hmmm.
Any help here would be appreciated. I am lost and this is holding me and the project back. Is there something I am missing? Thanks all. This is why I love CPF forums!
-Tony