Design number 2

A project log for LED Light Rod

Battery powered led light that looks like a fluorescent tube light.

Mackenzie HauckMackenzie Hauck 05/31/2016 at 05:410 Comments

So after the first idea didn't pan out I went back to the drawing board. One of the biggest problems was trying to fit the battery inside of the metal framework for the leds, and thanks to geometry if I add more sides that means I can decrease the outer radius. Basically lets me make the metal structure fit more tightly around the batteries as well as having more lights around them to hopefully get me 360 degree light distribution a little easier.

Looking at the current renderings right now you would notice that there is a large gap between the battery and the metal. This is to allow room for a 1" OD acrylic pipe which will make up the outer shell of the battery module. I have a 3D printer so I was thinking I could 3D print it instead to add things like cable management right into the holder. Another limitation is the width of the actual led strips. With the current model the sides of the hexagon are almost at their smallest possible size. I could move down to the smaller SK6812 strips which you can get in strips that are something like 3 or 4 mm wide(!) but those strips don't come in rgbw, and I wanted to get a nice pure white from the rod since it is meant to sorta emulate a fluorescent bulb.

The power delivery method also changed. Originally was using 3 LM2596 modules from ebay which could theoretically get me 9A with good heatsinking, but since I'm using 720 leds now I need a bit more power... I am instead going to use Pololu's 5V 9A buck regulators, probably 2 or 3 of them for either 18A max or 27A max output with good heatsinking. I also needed to up the batteries to 6 18650 cells. I might upgrade the batteries in the future as the ones I bought a while ago can only do 2C max (around 6-7A per cell in my case) and they are starting to be a limiting factor in the power section. I figure I can get around 90W out of the 6 batteries I have right now so 2 buck regulators would be enough, but I was thinking of future proofing in case I move to better batteries and with more regulators to share the load they wouldn't heat up as much individually.

Of course I haven't tested the thermals of all this stuff yet so I will probably be under driving the leds and regulators to save on heat output. That's probably the biggest issue/unknown right now.