doubt in rc circuit about charging time

[Bhuvanesh Nick]

is my above circuit correct

!my idea is to to on the led after some times..to do so how to calculate the time

 

[phobos1]

h**p://www.electronics-tutorials.ws/rc/rc_1.html
hope this helps u to some level. good luck

 

[Bhuvanesh Nick]

https://www.electronics-tutorials.ws/rc/rc_1.html
hope this helps u to some level. good luck

thanks PHOBOS1 it helped me

 

[vyomax]

charging equation of RC series circuit.
vc = v(1 - e-t/rc)

In this case capacitor will never charge more than 0.7 V that is LED's forward voltage drop.

 

[Bhuvanesh Nick]

charging equation of RC series circuit.
vc = v(1 - e-t/rc)

In this case capacitor will never charge more than 0.7 V that is LED's forward voltage drop.

from what i learned capacitor charges 60% of supply voltage and then it supplies for led .am i right

 

[kripacharya]

charging equation of RC series circuit.
vc = v(1 - e-t/rc)

In this case capacitor will never charge more than 0.7 V that is LED's forward voltage drop.

Actually that equation works only upto the point where LED current is very very low. Once the voltage reaches the diode knee, this is no longer valid.
Secondly, I know of no LED whose knee is as low as 0.7v. LED's are typically 1.6v .. 3.2v depending on the colour.

 

[vyomax]

Actually that equation works only upto the point where LED current is very very low. Once the voltage reaches the diode knee, this is no longer valid.
Secondly, I know of no LED whose knee is as low as 0.7v. LED's are typically 1.6v .. 3.2v depending on the colour.

Actually u r right. LED produce around. 1.3v
I just considered it as a pn junction diode.

- - - Updated - - -

from what i learned capacitor charges 60% of supply voltage and then it supplies for led .am i right

The equation is just for reference
in your circuit it is not valid for all t (time)

Capacitor will charge only upto forward drop across LED. remain there forever
It will not charge upto 60%

 

[Bhuvanesh Nick]

Actually that equation works only upto the point where LED current is very very low. Once the voltage reaches the diode knee, this is no longer valid.
Secondly, I know of no LED whose knee is as low as 0.7v. LED's are typically 1.6v .. 3.2v depending on the colour.

Sir,capacitor has infinite resistance.so in that way,why dont it charges first and then supply it to led