After putting together the LEDs for the grow lamp, and having initial success the next problem was that the LEDs themselves would heat up to be too hot to touch within about 40 seconds. If I left them switched on, I am sure they would have melted :( The stock heat-sinks they recommend to use are woefully under size.
I have procrastinated about this for ages and yesterday got around to doing something about it. So I went with the traditional solution and got a big heatsink :)
Step 1 - was to re-wire the LEDs into a more compact configuration than the straight line they were in before. I thought this would be easy with the hexagon design of the star LEDs, but actually they don’t lend themselves to be hooked up in serial – this was the pattern I came up with:
Notice the top-left LEDs don’t mate correctly :( – So I added a wire link to get around it.
Once cleaned up and soldered into the new configuration – I got the largest heatsink I could without making it look completely over the top:
With some hand-drilling, mica paste and the final of Masterchef later I had it all put together:
I ran it last night for about 1hr 20min and while it did steadily get hotter, it was still cool enough to pick up and didn’t melt the solder or kill any of the diodes which is good enough for me :)
Now this is only 12watts of LEDs running through a ~700ma current limiting device.
The next step is to hook it up to a 20watt halogen lamp that I got at Cheap as Chips for $15. I have removed the bulb assembly and will use the lamp base as the power supply and the will make it easier to position and direct the light a bit more. In theory the 20watt lamp should be able to handle the 12watts of LEDs – however I will take more photos just in case it all bursts into flames :)
Continues in Part 3