START OF THE JOURNAL

dumping my brain

inspired by this

issues with the existing ones

battery is fairly small 40w max power with a 4000mah battery isnt great 4000mah * 3.7v = 14.7Wh 14.7/40 *60= 22min battery life at max power

bms? diy or something else

couple of rotary encoders for brightness and temp

rp2040 mcu perhaps custom pcb for everything???

perhaps i do

power, charging, mcu, pots and all that on one pcb then have that connect to another PCB with the other PCB only being LEDs

with the intent of that being the front pcb

part selection

• what ic to use for usb pb? HUSB238

  • allows for selection of voltage and current with simple resistors, no need for i2c
  • not sure on availability
    • look for alternatives??

• 18650 cell with 4000mah capacity

  • assuming worse than the worst case, and the circuit draws 120w
    • (planned max draw is 80w)
    • then 120w/3.7 = 32a
    • split that between 6 cells
    • 5.5a per cell
    • https://www.fogstar.co.uk/collections/18650-batteries/products/fogstar-energy-4000-18650-battery
    • these are rated for 10a per cell
    • nominal v = 3.6
    • 10a x 6 x 3.6 = max theoretical power of 216w, ample

• use a relay for the first power stage

  • relay defaults to being powered by battery
    • once mains is connected, it powers relay and switches over to the usb power
    • add diodes to prevent back powering the relay from the battery

• which LEDs to use

  • needs to be fairly high power
    • rules out neopixels since would need a larger number
  • also needs to be fairly high CRI, 70+, ideally 80+
  • not a massive footprint, i need to be able to have a grid of them so they blend nicely without massive hotspots
  • found the lumileds, LUXEON SunPlus 5050
    • available in 6v or 24v , current would start getting ridiculous at 6v 24v seems smarter
      • the 24v have cri of 80 instead of 90, but 80 is already good
  • ideally i want some warm, and some cold so i can blend
    • 2200-3000k for the warm, 9000k for the cold
      • those lumileds are available above 6500k, but i think thats good enough, i tend to like warm lights anyway
  • this lands us with the following LEDs

  https://www.mouser.co.uk/ProductDetail/997-L150228050240H - specs - 6500k - 24v @ 160ma , 3.8w - 650 lm - 80 CRI

  https://www.mouser.co.uk/ProductDetail/997-L150658050240H - specs - 2200k - 510 lm - 24v @ 160ma , 3.8w - 80 CRI

• mosfet for switching the LEDs

  • https://www.mouser.co.uk/ProductDetail/771-PMV20XNER
    • power disipation of 1.2w
    • 30v max power
    • sustained current @ 25c = 5.7a
    • sustained current @ 100c = 3.6a
      • 3.6a @ 24v --> 86.4w
      • i will have the current split across two of these anyway, one for the warm LEDs, one for the cool LEDs
  • https://www.mouser.co.uk/ProductDetail/511-STD17NF03L
    • NEW MOSFET significantly more expensive,
      • 0.621 vs 0.145
    • sustained current @ 25c = 17a
    • sustained current @ 100c = 12a
      • 12a @ 24v --> 288w

if i did 24 of each thats 48 total 24 * 3.8 = 91.2w of each temp total power = 182.4w 55680 lumens of light :skull: max

using 6, 18650 cells gives me 88.8Wh of capacity which is alot better than the default similar battery life at max power, but max power would be very rarely used

start of the cad and PCB

just got my 18650 battries modeled