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[SOLVED] Current limiting resistor

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umashankar

umashankar

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Dear All,

Why we need a current limiting resistor for a LED circuit ?

i am using a LED Circuit for Standby purpose , Which can be controlled by a transistor switch .
i kept the LED and a current limiting resistor on collector side of the transistor, once if the transistor is ON
the LED will glow , if its in OFF the LED remains in OFF.

Here the LED is in front of the resistor,the other end of the LED has been tied to VCC.

will it cause any issue, can you pls help me to sort out this ?

Ref : Schematic attached
 

Hello
first something wrong with your attachment because i cannot see it ,
as a matter for the limiting resistor , we use it so the LED wont burn due to over current , also to protect the outputs of the connected devices at time when it does not support large current
as far as i know , your LED will not need resistor if the applied voltage is just above the forward bias voltage, however it is not recommended to use a LED without a current limiting resistor.
Regards
 

umashankar said:
Dear All,

Why we need a current limiting resistor for a LED circuit ?

i am using a LED Circuit for Standby purpose , Which can be controlled by a transistor switch .
i kept the LED and a current limiting resistor on collector side of the transistor, once if the transistor is ON
the LED will glow , if its in OFF the LED remains in OFF.

Here the LED is in front of the resistor,the other end of the LED has been tied to VCC.
i
will it cause any issue, can you pls help me to sort out this ?

Ref : Schematic attached
Click to expand...

Hi, resistor is used to control the input current into the LED. High current will damage LED.
 

umashankar said:
Dear All,

Why we need a current limiting resistor for a LED circuit ?

i am using a LED Circuit for Standby purpose , Which can be controlled by a transistor switch .
i kept the LED and a current limiting resistor on collector side of the transistor, once if the transistor is ON
the LED will glow , if its in OFF the LED remains in OFF.

Here the LED is in front of the resistor,the other end of the LED has been tied to VCC.

will it cause any issue, can you pls help me to sort out this ?

Ref : Schematic attached
Click to expand...

ThanX for the reply,
 

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