3W UV Leds... heatsink and powering question - Page 1
Forum section: electronics / projects

author: robotic
author_rank: Contributor
timestamp: September 25, 2017, 12:54:54 am
content: I'm planning to buy 60 or so UV LEDs. I want to make about 10 units to spread them around the room. The forward voltage ranges from 3.2 to 3.8v. Is it possible to do 3 leds in series and 3 of those series in parallel work? so 3(12v), 3(12v), 3(12v). The current is 700ma so about 2.1A I have a bunch of old PC power supplies I could use which can do 13A on the 12V rail. Can probably power 2 of them if they are close enough to each other...Another option is to buy LED driver... There are two options AC to DChttp://www.ebay.ca/itm/85-265V-300mA-600mA-LED-Driver-Convertor-Transformer-Ceiling-Light-Power-Supply-/252064252556?var=&hash=item3ab033428c:m:mDeBfrvHc0FMBdbXGv7CAUgonly 650ma (I think that would still work right?)or a DC to DC step-up constant current LED driver.. like this 30W onehttp://www.ebay.ca/itm/10w-20w-30w-50w-Constant-Current-LED-Driver-DC12V-to-DC30-38V-For-high-power-led-/321461904029?var=&hash=item4ad89f629d:m:mzUySLY-DzUYpp_fJGWZGcgWill these work?Second question is will this heatsink be okay for 8, 10, or 12 3W UV LEDs?http://www.ebay.ca/itm/1x-Aluminum-Heatsink-300mm-25mm-10mm-for-Led-Emitter-Diodes-High-Power/191931474269?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2060353.m2763.l2649I could try to add fans to cool them as well. or I would go a cheaper route and get a L bracket aluminum bar and add a PC heatsink to it... not sure if that would work though.

author: Audioguru
author_rank: Super Contributor
timestamp: September 25, 2017, 01:32:50 am
content: 3W is probably the absolute maximum IF the heatsinks are perfect and the room is air conditioned. Yours might overheat at 2W or less.You must use a supply with a voltage high enough for a current-limiting resistor and 3.8V LEDs, maybe 14V or 15V and you must calculate the resistor to limit the current properly even if all the LEDs are 3.2V.

author: robotic
author_rank: Contributor
timestamp: September 25, 2017, 01:44:19 am
content: Well 3.5V will be my target i think. I'm buying some 2W resistors for 2.2ohm (based on the 'led' calculator')I'm thinking doing the 9 LEDs. Will that work?For the heatsink I might try something like what this guy didhttps://www.youtube.com/watch?v=MeV0ZpYeQ50.He only used 7 LEDs though =/. Is it possible to just add a heatsink onto the aluminum L-bracket with some thermal paste and screw it in and then use a cpu fan on it if needed. BAR -> attach a CPU heatsink -> attach a fan to the CPU heatsink. Will that dissipate enough heat? on the end LEDS if I place the heatsink in the middle of the bar.My other option is to mount 3 leds to a CPU heatsink and attach the three heat sinks together... to create a unit.

author: robotic
author_rank: Contributor
timestamp: September 25, 2017, 01:54:01 am
content: If I buy a led driver board like say this30W Driver:New and high quality, nice design, energy-saving, very strong brightness, waterproof, multifunctional, practical, durable, reusable, convenient.Driving power: 30wModel: 10series 3 in parallelInput Voltage: 85V~265VOutput Voltage: 33-35VCurrent:1050mAEfficiency > 88%Power Factor >0.98Operating Temperature: 20~80Does the 1050mA current matter? or do I need to find something with 700mA?