need variabl dc voltage of 24volts ....... urgentlyyyyyyyyy..... pls

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nirmal kumar

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need variabl dc voltage of 24volts circuit...... urgentlyyyyyyyyy..... pls

need variabl dc voltage of 24volts circuit ....... urgentlyyyyyyyyy..... pls pls its very urgent....pls
 

You can use LM317 if 1.5A covers your need, **broken link removed**
Use the datasheet schematic (increase the adj pot to get 28V) or search google for LM317

Alex
 
Hi,
It depends on your specifications. For 1.5A, LM317 is the easiest. For 3A check LM350. If you need an efficient power supply, you need to use switching regulators. In that case, you can use LM2576 or the L49xx series of regulators from ST.



This is a very easy circuit using an 8-pin L4971.

L4971 datasheet
LM317 datasheet
LM350 datasheet

Hope this helps.
Tahmid.
 
which is the variable resistor ...... and can u explain the how circuit works ....
 

The lm317 datasheet has all the details,
on the typical application schematic it has one resistor 240 ohm between the out and adj pin and one variable resistor (trimmer or pot) between adj and gnd.
The output voltage is calculated using these two resistors, it is 1.25v * (1 + Rtrimmer/Rout_adj)
use a calculator if you want **broken link removed**

Alex
 

Hi,
In the circuit provided, (using L4971), R3 can be replaced with a 30k resistor to obtain a variable output voltage from 3.3v to 24v with max 1.5A.

In this circuit, it's quite clear:


The original formula is Vout = Vref * (1 + R2/R1) + IadjR2, but IadjR2 is small so won't make a hell of a difference, so can be omitted. Vref = 1.25v

Hope this helps.
Tahmid.
 

@alex ..... thanks yar ...... it works ......
 

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