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led n00b here, need a little help

hey guys i am new to electronics and figured id start with leds, my first project will be to make a torth from a penguin caffinated mints tin using some domestic batteries, some Super bright (17000mcd) 3v Green LEDs and 10 resistors only described as "Used to operate a 3.3v LED on a 5v Power Line. " and the same for the 10 12v resistors. now can anyone tell me. when would i need a resistor in my circuit? (i know the one for the 12v line would be perfect for arraching to a car battery and not killing the led.) but the 5v resistors? when would i use them? when i make this torch i will be using 2 or 3 aa batteries, 2 aa batteries make 3v and these leds are meant for 3.3 so im assuming i wont need a resistor however if i used 3 aa (4.5v) would i need the 5v resistor or would it be to much? im sorry im confusing thanks

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Gjdj38 years ago
Cew27 (author)  Gjdj38 years ago
"Since you know these terms you can remember that electricity flows easily from the anode to the cathode but not the other way around." quoted from one of the above instructables, this is backwards thanks
electrons (negative current) flow from K to A he direction of electricity flow (positive current) is opposite to that of electrons
Cew27 (author)  110100101108 years ago
oh right, my mistake
yea thats confusing (not that it bothers you when pikachu attempts to wake you up)
Gjdj3 Cew278 years ago
I'm pretty sure that I'm right about the anode cathode thing. Just google it.
Cew27 (author)  Gjdj38 years ago
also can i ask when making an led that blinks, why is a microchip needed? is this so that when the capacitor is charged the circuit is broken?
not necessary a chip. any circuit that switches on its own as wanted is ok this circuit can be 555 / 2 transistors / frequency divider from line ac voltage / thermal relay / relay / motor powered mechanical switches and other possibiitis
Gjdj3 Cew278 years ago
It's not exactly a microchip. It's an integrated circuit, and I believe the one you are referring to is a 555 timer. A 555 is normally used to make an astable circuit with pulses. By changing the capacitance and resistance of the circuit, you change the frequency (ie. How quickly the led blinks, The pitch of the noise from the speaker, etc.).
Cew27 (author) 8 years ago
wait, just remembered why i got confused, i wasnt told the current rating of my leds just the operating voltage and the brightness
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