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HOW TO USE 7805 AS VARIABLE VOLTGE REGULATOR

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sokrat

sokrat

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HI ALL

THIS IS SIMPLE METHOD TO USE 7805 AS VARIABLE VOLTGE REGULATOR WITH CONNECT VARIABLE RESISTOR(0 TO 5k) FROM PIN 2
TO GND THE OUT WILL BE 5V TO 22V WHEN YOU CHANGE THIS RESISTOR



I USE PROTEUS 6.1 SP1


THANKS

S 8O KART
 

As long as the DC input has no ripple it looks OK.

The problem is that the ripple rejection is not very good. You have to bypass the resistor to GND with a fairly large cap (100uF or so).

If you substitute your input batt with say a 100Hz sine source with say 1Vp-p amplitude and a DC offset of +24v and connect a scope on the output you will see a nice sinewave on the DC at the output.

E
 

I think that the input Vp-p should be large.
 

uses TL431 voltage reference replace the res on Pin2 to GND should better.
But the the Vout have to be 7.5v and above.
 

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