Hi folks. Sorry for butting in like this. I’m trying to build a small mason jar aquarium and looking to house a 3w cob led like this: https://www.ebay.co.uk/itm/113886781401

in the lid of a jar and have it powered via micro USB using a breakout board like this: https://www.ebay.co.uk/itm/123257921572

I’m really struggling to find out how to set up a resistor etc on this breadboard prototype. I am not good at this. Can anyone give me a steer? I feel like this is very basic but perhaps I’m missing something.

everything I try (220?) my Mac tells me to unplug whatever I just tried because it’s using too much power.

I am so over my head and appreciate any guidance. I have a decent selection of various resistors and am completely colourblind. Theyre labelled up which helps but yeah. I’m defeated.

 

hi Battt,
Welcome to AAC.

3Watts/3.2V = ~0.9Amps.

5Vusb-3.2Vled = 1.8V..... 1.8V/0.9A = 2 Ohms .. 1.6Watt resistor, say 3Watts.
E

 

The LED will fail in probably less than 1 minute unless you cool it properly with a heatsink that is designed for it.
But old USB will not provide enough current for the LED to operate anywhere near its max current.

 

Thank you both - so in terms of the original idea, a 2ohm resistor is preferable.
Taking into consideration the advice above around the current etc - I am not set on the design - what would be optimal? My only real requirement is that it’s fairly discreet as I want to mount it on top of a jar. Appreciate your time - thank you.

 

hi B,
Without a Heat sink, the LED will run over-hot.
Buy a 5Vdc 2A Wall Wart Power supply.
E