is it enable reduce 12v to 1.5v?

[AccordRacing]

just now i go to pasar malam,i saw a LED stuff like the branded PIAA 6 LED in line and cost around rm400,it plastic quite bright n got 2 option,1 is flashing and others is keep it on,5 LED in line,the purpose of this thing is let others ppl mention and its can bang at ur head,i just wonder wheither its can mod to car bumper which its using 3 AAA battery inside(1.5v) and car is 12v,can mod it?i c the price around rm20 still can nego i think,some 1 pls help me solve this problem

 

[acbc]

To reduce voltage to 3V from 12V (esp for LEDs), just put a 1k ohm resistor on the positive side. Or you can also use 330 ohm.

 

[AccordRacing]

how to call that thing n specific?wher to buy?

 

[acbc]

1k ohm resistor - most electronic stores will know.

 

[khguan]

de pasar malam thing with LED is using 3 batteries... but r u sure it is 1.5V?? dats true if it connects in parallel...

but i think it connect in series.. making 4.5V..

u mean u wanto use dat whole thing on ur bumper? well u can try n use 470 ohm 0.5W resistor connect in series then connect to ur car power supply... if too bright... use 1K ohm

 

[kruger]

waaa.... khguan, you quite good at ledeeeying thing ni ha...??? :)

 

[n305er]

Wait wait...
You mean you want to connect a 12V LED and power it up by using a 1.5V battery or use a 1.5V LED powered by 12V battery fom your car??

 

[cipan_supercas]

So,... u want to reduce the 12V car battery power supply to 4.5V...????
Easy... use a 5V voltage regulator.
part no of the ic is 7805.

what u need:
7805 power regulator ic.
470mF 25V capacitor
47mF 16V capacitor.

Want a precise 4.5V...???
no problem... use LM317T... but it's more complicated to built.

How to contruct?
See me... i'll show u how.

Do not use the serial resistor configuration as what been suggested by our friend... That is just a current limiting configuration which will surely fry your electronics. Unless... if u only want to light up the led directly using the 12V supply... yes u can drop the current by using a 1k2 resistor connect in series.

How to calculate?
Again... see me.

 

[khguan]

Originally posted by kruger@Mar 14 2005, 02:24
waaa.... khguan, you quite good at ledeeeying thing ni ha...??? :)

no lar... i onli know basics. hehe :lol:

 

[khguan]

cipan_supercas,

yes.. ur method also good.. but need more cost n time to build it...

it is not 470mF 25V and 47mF 16V capacitor... it is 470uf n 47uf..

"m"represents milli.. where "u" represents mikro.. actually "u" also wrong.. bcos we cant use de symbol "miu" in text.. so we use "u" B)

btw.. i dun think u need perfectly accurate 4.5v for de LED thing.. 5V also wil do... not much different from de margin..

 

[votech]

Originally posted by cipan_supercas@Mar 14 2005, 07:32
So,... u want to reduce the 12V car battery power supply to 4.5V...????
Easy... use a 5V voltage regulator.
part no of the ic is 7805.

what u need:
7805 power regulator ic.
470mF 25V capacitor
47mF 16V capacitor.

Want a precise 4.5V...???
no problem... use LM317T... but it's more complicated to built.

How to contruct?
See me... i'll show u how.

Do not use the serial resistor configuration as what been suggested by our friend... That is just a current limiting configuration which will surely fry your electronics. Unless... if u only want to light up the led directly using the 12V supply... yes u can drop the current by using a 1k2 resistor connect in series.

How to calculate?
Again... see me.

this is the most reliable method...although more complicated than using the series current limiting resistor.

by the way "m" is "miu" and not pronounced as "U"...its actually a small letter "m" widely used in science subject.

 

[khguan]

in sciece subjects.. de letter "m" is refered to milli... not micro..

de caps we use is micro farad... not milli farad... (1000 times bigger u know?)

 

[votech]

Originally posted by khguan@Mar 14 2005, 12:56
in sciece subjects.. de letter "m" is refered to milli... not micro..

de caps we use is micro farad... not milli farad... (1000 times bigger u know?)

i think my explaination is same as urs on the "m" thing lah...that's y i say its pronounced as "miu" and not "U". And trust me, i know very well that milli is 1000 times of a micro. ;) and "miu" looks like a small letter "u" and if u type on the keyboard, its small letter "m" which is also not wrong in this case :P

 

[drexchan]

talking to engineer and scientist? haha!! I think votech is correct..

 

[khguan]

ok... i get wat u mean... n wat u r trying to say...

anyway.. de character is "µ" dat represents micro.. n de symbol is pronouced as "miu" rite?

off topic liao.. :P

 

[votech]

yup..u got that right.

well, back to topic, i will still recommened the use of a simple regulator circuit to reduce the voltage instead of using current limiting resistor. a simple regulator only take 3 components to built (1 regulator IC and 2 capacitors to be used as filters).

 

[cipan_supercas]

elo bros....

1pc 7805 = RM1.50
1pc 470mF/uF what so ever u understood = RM 0.60
1pc 47 mF = RM 0.40

only RM2.50 for a guaranteed diy that will not smoke ur electronics.

how can u said very expensive one????

If u only put in a resistor in series ... i know for sure it will smoke....
how i know?
i know larrr....
u also got learn electronics what... how come u don't know....
if u put a resistor in series... i told u already... it's just a current limiting... it means that only the current is limited/dropped, but the voltage remain the same....
unless u do a voltage divider circuit which is not that reliable... u have to know the total power consumption of the whole circuit to be fired...
so, the most efficient one... use the power regulator...

 

[AccordRacing]

wow...tats mean really can make it lar..oh i gonna try it,coz the LED stuff is damn bright n not so costly,if compare to PIAA,even get stolen also wont cause heart broken,hehe :D

 

[sam1741]

i think..
cannot use resistor alone

cause the voltage and amp is different
when car idle and moving..

better use regulator.. easy to made only..

7805 is for 5v one

LM2937 one i think got 3v one.. (not sure)


if i not mistaken 78xx series regulator
can tolerance up to 30v
so no need to worried about input voltage..


but remember to supply your regulator with a heatsink

 

[khguan]

for low ampere usage like LEDs no need heat sinks....