i have previosly played around with a couple of LEDs from radio shack and the bulbs are 3.7volts min and 4.5 volts max and i did the equation that Illusion had on his website:thumbup:, and he recomended 470-Ohm resistors and i got the ½ watt ones and used them and they came out fine
i went to radio shack yesterday and i saw that they had 470-Ohm ¼ watt ones so i picked up both

so my question is do i use the ¼ watt ones or the ½ watt ones

Thank you,
RY2K

here is a picture, it's hard to read so i drew on the pic


i want to do this the correct way, and not mess up my car so i apreciate any input

 

wattage is a measurement of power. the wattage rating on a resistor is basically how many watts/milliwats it can safely dissipate as heat. i'd go with the 1/2 watt ones. better to be safe than sorry.

 

Whats the equation you used to figure this out?

 

I usually use 220 ohm.....but da jus me.

If anything is to get screwed up by using the wrong resistor, it would be the LED itself and nothing else....feel free to correct me if im wrong

 

Ohm's law E=I/R :dunno:

 

ok so i'll use the 1/2 watt, i didn't know about the heat

what is the voltage of the LED you use the 220 ohm resistor with, and does it make it brighter


thats good to know cause my friend got me worried, i hope you're correct:happysad:

E = I*R so R = E/I



check out the web page it's explained really well
http://www.igd4u.com/modules.php?op=...=article&sid=2

 

:doh: i knew that.... it's been a while since i used it though

here's the extended equation to calculate power in a circuit.



using W=E^2/R you'll see that the 1/4 watt resistors won't cut it. and a burning resistor don't smell good at all.

 

thanks for the equation picture

my car smells like cucumber melon, and a burnt resistor would not be very :grinpimp:

 

yeah, that ish smells like ass... i used to burn one every morning in electronics class in high school just to be an asshole:thumbup:

 

I go with the 220 ohms with the 3.5v. It's the best combo 4 leds and resistors.