calc calls for 270ohm 1/8 watt??

Thread Starter

mvp

Joined Jan 21, 2014
9
Wiring 4 led parallel. calculator calls for 270 1/8 watt resistor. Is it ok to go 1/4? Cant find 1/8 locally.
4 led, 12v, 3.6, 20ma
 

shteii01

Joined Feb 19, 2010
4,647
Yes, it is fine, it gives you more "safety room".

1/8 W is 0.125 W.
1/4 W is 0.25 W. So, if for some reason you made a mistake somewhere and have more than 0.125 W power at the 0.125 W resistor, the resistor will break because it is not build to dissipate more than 0.125 W, but if you use 0.25 W resistor, then resistor will survive. Unless you exceed the 0.25 W also.
 

tshuck

Joined Oct 18, 2012
3,535
Yes, (c)..sorry, I'm new to this
No worries, but there are some nuances with LEDs. Actually putting them in parallel will cause them to share current differently, making some light and some dim. Then some melt and the others light, then they all become dim forever.
 

mcgyvr

Joined Oct 15, 2009
5,394
Always double (or triple) the calculated wattage for safety and to keep it from running so hot.
But yes always ok to go higher on the wattage.. never lower.
 

shteii01

Joined Feb 19, 2010
4,647
No worries, but there are some nuances with LEDs. Actually putting them in parallel will cause them to share current differently, making some light and some dim. Then some melt and the others light, then they all become dim forever.
Like the above said, in parallel there might or might not be some variation in brightness between the parallel branches. To even out the brightness, you may have to "play around" with resistors. Put a slightly larger resistor at the brighter branch or put slightly smaller resistor on the dimmer branch, or do that to both branches.
 
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