Im wanting to use this in cab dome light insert from a truck (12v) to make a desktop lamp, but instead of adding a step down circuit, can i change something here to get it from 12v to 3v ?
Im pretty sure a resistor swap to a much lower value would work, not zero i wouldn’t think, but what about the other part, a google tickle says a shunt, should it be removed ?
And i have a small 5 amp pwm id like to use as the on/off and brightness adjustment, but it says for 5v-30v… would it be able to work at 3v-4v as for a 1s battery ? A simple try it and find out is a no brainer..
Again sorry if this should be in a different section of the forum.
I guess the simplest solution would be to use a 3s-4s pack… but id need to order a 3s-4s charging circuit.. that might be a better deal anyways as it would give a better platform to stand on ?
I was going to use a 3 slot 21700 holder, one battery in each outside slot in parallel and the 1s charging circuit and pwm in the center slot.. 2 steel rods bent and covered as the stalk and power leads, and this led board as the lamp..
It would be alot more than 3-4.2v
Ive hooked up just an cob led and it comes on at 2.9v and gets hot at 4.1v thats the highest it puts out.. got enough circuit to have a bit of power loss.
Yes i want to alter the pcb to be used with a 4.2v pack.. seems all of the leds are in parallel.. so should come on as normal, like 2.9v and go upto the 4.1v my output has.. so im basically just needing to remove and jump the resistors, or put in 0 ohm units..
mainly asking shoud i direct jump the resistor lines… ?
It needs a low value resistor… ?
And should i leave the 4 legged thing or remove it as well ?
I just like the shape/form factor of this led board and didnt want to run it at full 11-14v
This is not a good idea you need a way to regulate the current.
Its a rectifier. you don’t need it. you will loose around 0.5-1 volt in this part.
There are LEDs with 3 leds in series in one package.
this light would be a inefficient and wasteful design if they don’t put 3 leds in series.
To go from 12V to 3V in a resistor you waste 9V in the resistor
if they would uses 3 LEDs in series the resistor would only need to burn off 3V and the whole thing would stay way cooler.
Ok remove the rectifier, replace the 750 resistors with say 100 ?
And this pwm isnt a good fit for this, ill remove it and just put a simple on/off switch.. so to have it at the power level i want i need to just keep lowering the resistor value till i get the brightness i want with the voltage i have available (3-4.2v) correct ?
I honestly cant see the leds in anything but parallel, all of them are set in the same orientation to one another (as seen through the coating, and seems the top line (negative) runs all the way across.. definitely could be wrong about that tho..
And i thought a rectifier was only used to conver A.C. to D.C. ? Why would one be used in a 12v D.C. part ? Incase you installed it wrong ? It has to face down..
Google search suggests the rectifier is there to limit current to 0.8a -1amp.
ETA: if that is correct, that would math out to around 20ma per led, which sounds about right.
But I think google may be hallucinating. Hehe
