how to convert 12V to 3V for LED light in car !

[limandy]

All Sifu,

Can teach me how to do.

 

[kruger]

All Sifu,

Can teach me how to do.

i tought this topic has already been discussed. try search it lar... :) btw if you put 1k resistor is enough already at your led...

 

[khguan]

yep.. just use a 1K resistor.. kau tim...

 

[sam1741]

ya... use 1k
very cheap also
few cent only... :D

 

[kage2099]

guys... the 1K Ohm resistor got many many different watts... got 1/2W, 1W...........etc... last time i wana put LED on my VS i ask the electronic shop for 1K resistor and they asked me wat watt u wan... i duno wat to answer...

so... sifoo sifoo sekalian... which watt is ideal to be used lehh??

 

[khguan]

for LED... 1/4W is more than enough..

 

[jswong]

Wa lau eh! Put 1k resistor is good enough? Hmmm.. so that means the resistor will soak up all the rest of the voltage? (3 volts for LED, 9 volts for resistor).

I think we can also make a 5-volt regulator using a single 7805 IC.. safer that way. Besides, direct 12 volt in car wiring can run high currents also.

 

[jaywat]

like that not really cost effective...some more add up complexity...being using 1k resister on my LED in VS so long already ...now still as bright as ever.

 

[khguan]

jswong,
no prob lar dude... dun worry... LED taking very little current onli.. therefore the current that pass tru de resistor also very little.... go n learn more about basic electronics then u know y...

 

[sam1741]

if u wan regulator...
got one for 3.3v also..
but forgot what code...
something like 7829 or something

 

[lcchong]

jswong,
no prob lar dude... dun worry... LED taking very little current onli.. therefore the current that pass tru de resistor also very little.... go n learn more about basic electronics then u know y...

the resistor will heat up or not?

 

[sam1741]

wow... such an old thread
anyway, since that time (4 years ago) until now
there is a better solution

using LM317 regulator
(the sample circuit is inside the data sheet)

u can limit the current for the LED (normal one, 20mA is more than enough, i have high power LED running at 300mA which is very hungry beast)
or , can limit the voltage (e.g. 3v for normal LED)

and best thing about LM317 is u just set the limit
no matter the input voltage goes until how much (but there is a limit, i think 37volt)
the limit u set will be the same

 

[lcchong]

instead of the LM317, can we connect 4 pcs of LED (3v) in series?

----(+)LED(-)--(+)LED(-)--(+)LED(-)--(+)LED(-)---(+)LED(-)----

then can directly connect to car (+) power????

Bump: find the suitable resistor for your LED...........

using this online calculator.....!

http://metku.net/index.html?sect=view&n=1&path=mods/ledcalc/index_eng

http://www.theledlight.com/ledcircuits.html

Bump: find the suitable resistor for your LED...........

using this online calculator.....!

http://metku.net/index.html?sect=view&n=1&path=mods/ledcalc/index_eng

http://www.theledlight.com/ledcircuits.html

 

[khguan]

if 1 LED kaput.. then all wont light up...

 

[lcchong]

aiya.........