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Help me for simple led drive circuit

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mastertushar

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i have 6 volt 4.5Ah battery and want to drive 30 White LED 5mm each LED @ 40mA current with constant current .

but my problem is that i have not to use any inductor in the circuit. plz suggest me any circuit.

see image i have to give regulated 4 volt to this array from 6 volt battery

40_1313168569.jpg
 

Without an inductor or transformer you're not going to be able to make an efficient converter, so you might as well just feed them all with as simple 1.2A linear current source, as they are in your schematic.
 

Hey my friend!
Hi
I confused ! in this circuit you don't need an inductor. why you want to use an inductor in this circuit?
i think you want 4 volts from 6 volt for your LED's . is it right? if it is right , and if you don't want to use resistor for your aim, you will have many way to obtain your purpose! in first step please say to me that my thinks are right?
Goldsmith
 

Basically you are asking for a 4V regulator. If you can't use inductors you can still use a PWM regulator which would be fairly efficient. If you are starting with a known 6V and the current is a constant 1.2A you can just use a single series resistor of (R=V/I) (6-4)/1.2 which makes 1.66 Ohms rated at 2.5W It wont be as efficent as a switching regulator but it is only one component and it isn't an inductor!

Brian.
 

Without an inductor or transformer you're not going to be able to make an efficient converter, so you might as well just feed them all with as simple 1.2A linear current source, as they are in your schematic.
thats what i need.

---------- Post added at 06:23 ---------- Previous post was at 06:13 ----------

Hey my friend!
Hi
I confused ! in this circuit you don't need an inductor. why you want to use an inductor in this circuit?
i think you want 4 volts from 6 volt for your LED's . is it right? if it is right , and if you don't want to use resistor for your aim, you will have many way to obtain your purpose! in first step please say to me that my thinks are right?
Goldsmith
as i need consatnt 4 volt from 6 volt so most preferred ck is of converter using inductor but i don't want to use it .. that's why i m asking

---------- Post added at 06:25 ---------- Previous post was at 06:23 ----------

can be that like this?
10_1313179039.gif

ya this one is write but i dont have this ic in my local market . and actually that reason of not using any inductor is same..

---------- Post added at 06:28 ---------- Previous post was at 06:25 ----------

Basically you are asking for a 4V regulator. If you can't use inductors you can still use a PWM regulator which would be fairly efficient. If you are starting with a known 6V and the current is a constant 1.2A you can just use a single series resistor of (R=V/I) (6-4)/1.2 which makes 1.66 Ohms rated at 2.5W It wont be as efficent as a switching regulator but it is only one component and it isn't an inductor!

Brian.

u are right but i want 4 volt from 6 volt battery as battery voltage is not constant at all but i want to drive led with same intensity. so battery voltage may become 5 volt or may 4.9 but i want 4 v at LED panel.. that's why only resistors not be solution.. i want to make linear regulator from transistors.
 

Oh my friend!
Hi
Why you don't use from LM39 14 IC ithink it can being useful for you.
But if the number of your leds are more i can send you a simple circuit that can help you.
With lucks
Goldsmith
 
Ok . you can use your leds on RL terminal. my mean is if you open RL you can put your leds in this terminal.led.JPG
If you rotate the multi turn (R7)., you can select your out put voltage precision= 4 volts. your transistors don't need heat sink.
I hope being helpful.
All the best
Goldsmith
 
@goldsmith
thanx a lot for that. i will try and reply here . but as how much minimum possible voltage across the 3055 as suppose my battery voltage is 4.2volt then i think its not possible to have 0.2 voly across transister
 

in first topic you said that you have 6 volts battery. not 4.2 volts.

---------- Post added at 11:12 ---------- Previous post was at 11:10 ----------

if your battery is 4.2 volts and you want 4 volts , you can use From this IC: lm3914
 

in first topic you said that you have 6 volts battery. not 4.2 volts.

---------- Post added at 11:12 ---------- Previous post was at 11:10 ----------

if your battery is 4.2 volts and you want 4 volts , you can use From this IC: lm3914

ya ya u r rite my battery is 6volt.. but after use of its voltage starting decreases .. i m saying when it's volyage becomes 4.2 volt :)
 

You have re-specified different design parameters and still left the most important one out. Initially you said you had 6V available, now it's 6V maximum. What is the MINIMUM battery voltage you need it to work at? Knowing the range of input voltage determines the type of regulator you choose. Also, how critical is the 4V LED supply, why does the LED brightness have to be kept constant?

As for inductors, if you can't buy one in the local market, why not make your own? Of all the hundreds of component types, inductors and low value resistors are probably the only ones you can make at home!

Brian.
 

You have re-specified different design parameters and still left the most important one out. Initially you said you had 6V available, now it's 6V maximum. What is the MINIMUM battery voltage you need it to work at? Knowing the range of input voltage determines the type of regulator you choose. Also, how critical is the 4V LED supply, why does the LED brightness have to be kept constant?

As for inductors, if you can't buy one in the local market, why not make your own? Of all the hundreds of component types, inductors and low value resistors are probably the only ones you can make at home!

Brian.

battery max vol 6 volt ,,, minumun volt 4.5 volts, output voltage of regulator 4 v . @1A .

and i cannot make inductor bcoz i dont have anything to measure inductance.. as i m engineering student
 

Why you dont want to buy a simple lcr meter?
Do you have oscilloscope?
with oscilloscope and one capacitor you can guess the value of L.
 

Then can be that in this sort? Vcc for NE555 4,5 - 18V.

(taken from http://www.reuk.co.uk/LED-Dimmer-Circuit.htm )
and i cannot make inductor bcoz i dont have anything to measure inductance..
So this not in principal..
MC 34063 for functioning is not required accuracy in selecting the inductor.
And it is uncomplicated, do meter for aproximate estimation of inductances
 
Last edited:
I think you are going to use the 6v 4.5Ah rechargeable battery. Right?

But are you sure that it is safe to use that battery when it's voltage become as down as 4.5v?
But I doubt it is not good for the life of a rechargeable battery ...Any way, I am not sure, but just confirm it before doing it..
 
Last edited:

I think you are going to use the 6v 4.5Ah rechargeable battery. Right?

But are you sure that it is safe to use that battery when it's voltage become as down as 4.5v?
But I doubt it is not good for the life of a rechargeable battery ...Any way, I am not sure, but just confirm it before doing it..

ya u are right i m using 6v 4.5Ah battery .. but tell me how much minimum voltage at which i can use that battery?
 

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