1watt 350MA led drive by 12v battery, circuit required.

[drbizzarow]

Dear All
I need circuit or help for 1watt 350MA led drive by 12v battery. Pls share yr help

Thx and Regards

 

[poorchava]

Have a look at LM317T datasheet. There is an excellent application circuit for driving led diode

 

[mishra12]

are you looking for microcontroller based led driver circuit ?

 

[drbizzarow]

i think LM317 circuit is not effeicent in term of heat and long life.
if it is reliable then it can be through microcontroller also.

 

[ZASto]

Why do you think that LM317T is not efficient?
You can then try 7805 (beware that then you will be cooking come coffee on the 7805, that is inefficient)

If, on the other hand, you need more efficient stuff, take look at the A1314S (Aimtron) or AP8802 (Diodes INC)

 

[poorchava]

LM317T is a simple solution, but there is simpler - a resistor. 1W diodes usually have about 3.5V forward voltage drop, adding a 33 ohm resistor in series limits current to 350mA.

More complicated solution is using ne555 as pwm generator + power transistor + feedback based on voltage drop on reference resistor connected in series with diode.

Why would anyone want to use a microcontroller for such a simple task? It's and epic overkill to use microcontroller for limiting diode current (especially that in that case u need a power transistor anyway)

 

[pranam77]

I have implimented and have circuits working with LM317. I never faced any problems. Afterall you need 350Ma which will be delivered even without any heatsink to a TO220 Package. Cheers

 

[drbizzarow]

ok pal i will try lm317 circuit and update

 

[Fragrance]

Hi

here you go it is good to used this circuit hope you will find it useful

 

[drbizzarow]

thx for every one who gave thier inputs

 

[alexan_e]

Why do you think that LM317T is not efficient?
You can then try 7805 (beware that then you will be cooking come coffee on the 7805, that is inefficient)

7805 can't regulate the output current unless an external circuit is used, in that case with the same output they would also have the same power consumption.
I assume that the previous poster meant that a pulse driver would be more efficient compared to a linear regulator.

I have implimented and have circuits working with LM317. I never faced any problems. Afterall you need 350Ma which will be delivered even without any heatsink to a TO220 Package. Cheers

It depends on the input voltage, in this case it is 12v and with an output of about 3.5v this leaves a voltage drop of 8.5v on the regulator,
8.5v*0.35=2.975W, he'll need a heat sink for that.

Alex

 

[poorchava]

The datasheet confirms what Alex wrote:
1. calculate power dissipated in regulator. In this case ~3W
2. calculate difference between maximum junction temperature and ambient temperature. Let's say 125 *C - 25*C =100*C (i assume that the device owill operate in room temperature)
3. calculate theta (or other greek letter. anyway - thermal resistance) which is ratio of temperature difference to power dissipated. In your case it's about 33 *C/W
4. check if the calculated thermal resistance value is greater than bare package thermal resistance (50 *C/W in case of lm317 in to-220 package). If it is, then u don't need a heatsink, otherwise u do. In your case you need some small heatsink thermally coupled to regulator with silicon sheet and silicon thermoconductive paste.

U can salvage an appropriate heatsink from broken PC power suplies which u can get for free or for some symbolic sum of money (like $20 for 10 broken PSU's - seen it like 2 days ago on ebay)

 

[Fragrance]

7805 can't regulate the output current unless an external circuit is used, in that case with the same output they would also have the same power consumption.
I assume that the previous poster meant that a pulse driver would be more efficient compared to a linear regulator.



It depends on the input voltage, in this case it is 12v and with an output of about 3.5v this leaves a voltage drop of 8.5v on the regulator,
8.5v*0.35=2.975W, he'll need a heat sink for that.

Alex

The best and good sulotion is o used LM2575 adjustable version from national semiconductor less part required switch mode effeciency 85% and plused out put i have done this with chip if required i can share schematic (there is also another chip they made which have capbility to adjust out put current and volt also i forget the part number but i can give it tomorow from my data sheet record)

regards
Fragrance

 

[drbizzarow]

i agree with FRAGRANCE sugestion....that is LM2575 adjustable version + very low resistence as a current limit.

 

[ZASto]

@Fragrance: LM2575 is purelly voltage regulator, 350 mA LEDs may vary in forward voltage from one to other specimen (even from the same batch).

A1314S from Aimtron
or
AP8802 from Diodes INC

are constant current regulators designed for LEDs in mind.

 

[Fragrance]

hi

this the best solution drive wide variety of led from 20ma 5amp which i mentioned in my previous post

regards
Fragrance

 

[MANAS R. PANIGRAHI]

Dear All
I need circuit or help for 1watt 350MA led drive by 12v battery. Pls share yr help

Thx and Regards

Well as these LED's require 3.6 to nearly 3.8 volts d.c so i've tried by combining three 1 watt LED's in series with a 2.2 ohm 5 watt resistor and a 5watt diode. its working perfectly in an alluminium encasing that acts an heat sink and it runs directly from 12.0 volt motorcycle battery.

 

[kak111]

Cheap, small led driver for 12 Vdc
https://www.onsemi.com/pub_link/Collateral/NUD4001-D.PDF

 

[mishra12]

KIA34063AF chip is the best solution so far i have used working perfectly