Continuing the discussion from COB LED Strips:
Pictures will follow!
I received the COB LED strips last Saturday and started working with them immediately. I want to share some insight w.r.t. saber building with this kind of strip. Don’t have any pictures as of this moment but I might post some in the coming days as I finish my current build. For reference, I ordered 3x1m 240LEDS/m RGB COB strips. Strips are 10mm wide and have a white silicon diffuser pre-applied. IP30 rated, protocol is WS2812B.
Power consumption and temperature
From my measurements the power consumption seems to be the same as what QuinLED showed in his spreadsheet (link to vid in previous post). A 1m strip consumes about 7.8W to 8.3W at full brightness for pure red, green and blue light. Compared to my SMD5050 144LEDS/m WS2812B, the power consumption is very uniform. At full brightness white, a 1m strip draws 5.3A at 5V, so about 26W. For reference, 1m of the 5050 strip draws ~4A at 5V for 100% red, while this COB strip draws ~1.8A at 5V for 100% red. Given the brightness I observed, I would argue that the COB LEDs are more efficient (again, see QuinLEDs video for more details on this).
In my design, I bent a 10mm x 11.5mm x 1000mm aluminium profile into a triangular shape with a pipe wrench. I attached a strip on every side. With a PT-100 element hooked up to my multimeter and shoved inside of the triangular profile (30cm in), I saw an increase in temperature from 22C to 58C over the course of about 15 minutes at ~75% brightness, switching between red, green and blue every 3 seconds. I estimate that when the strips are packed in diffuser inside a PC tube, they will not overheat if you only use them at 80%-100% brigthness (single color) for no more than 5 minutes in between cooling down.
Brightness and light characteristics
Given the smaller size of the LEDS on the COB strip, their lower power consumption and the pre-applied diffuser, the brightness of the COB strip for any color is dimmer than that of my SMD5050 144L/m strip. Where 100% green on a bare 5050 strip is unpleasantly bright to look at directly (it feels like it would hurt your eyes), the COB strip can be looked at directly for ~10 seconds before your eyes start to adjust and your peripheral vision starts to fade out. This is the main negative compared to the traditional strips, but again can be attributed to the lower power usage.
There are several advantages I have noticed, though:
- There is little cobbing (‘hotspots’ in the diffuser as a result of where the LEDs are located). At higher L/m (332, 480, 720) I expect this to be fully gone. This means that you need less diffusion material in your saber to make it look uniformly lit, resulting in less light being absorbed.
- The arc at which light is emitted is arguably 180 degrees with the pre-applied silicon diffuser. In any case, it is significantly better than SMD leds due to their well design.
- In terms of individual colors’ brightness, I rate them from highest to lowest in this order: green, red, blue. For the brightest sustainable result, you should probably go with 100% green, 10% red and 10%-20% blue.
The strips I linked are sold by TNALANT LED store on Aliexpress (no affiliation or sponsorship (sadly)). The build quality is decent: inter-strip connections are neat, the silicon diffuser contains no opague spots or defects, the adhesive underside sticks well. For about 13,- euro/m these strips are very good. While I have not tested any rainbow patterns or mixed colors (except white), I expect that due to the slightly dimmer blue and brighter green your color gammut might not be perfect, so keep this in mind if your build requires specific colors. As each LED is individually addressable, I am quite excited to try out some moving patterns.
Yesterday, I sanded my clear PC tube using a scotch brite pad for the first time (inside and out, length-wise movements, no twisting) after reading about it here. I was amazed at the effect this gave: I can only compare it to polished selenite. When I inserted the bare tri-strip light I built into the tube, the effect was quite unique and beautiful. You could clearly see the effect of the cobbing on the tube, but I would dare to say that if you eliminate that with 332L/m (or even 480 or 720L/m strips for single color), you will not need any diffusers anymore, because you can’t see the COB LED strips inside the tube. I’m quite excited about this and would like to investigate this further, although at this moment I don’t want to spend the money to get the higher-density COB strips (332L/m costs about 36,-).