A schematic from Colin e book.

[koolguy]

hello,
can we build this ?
how to calculate current from capacitor? as show in note?

 

[ericgibbs]

Hi,
Initially calculate the impedance of the capacitor for a 50hZ supply, using Xc = 1/[2*pi*50*C]
eg:
a 1uF at 50hz is 3183 Ohms, say 3800R, so with a 230Vac 50hz supply the current would be 230/3800 = 60mA RMS

a 0.22uF would be 14470R, giving ~16mA. RMS

NOTE: these figures are for an non rectified AC input

EDIT:
For safety, it is common practice to add a 10R to 100R resistor in series with the cap and also have 1meg ohm resistor across the cap.

 

[Willen]

For safety, it is common practice to add a 10R to 100R resistor in series with the cap and also have 1meg ohm resistor across the cap.

Yes, I saw in some devices as you said. Maybe series R is to minimise accidental spikes but what is the purpose of 1Meg across the cap?

 

[ericgibbs]

what is the purpose of 1Meg across the cap?

Just in case at the time of disconnection from the mains supply the capacitor is fully charged.
To avoid a possibility of a shock its advisable to place a high value discharge resistor across the cap.

EDIT:
Look at page #10 of this pdf.

Also:
https://en.wikipedia.org/wiki/Bleeder_resistor

 

[DerStrom8]

Ritesh, your previous thread that involved running LEDs from mains was closed because you have shown you cannot take direction and are endangering yourself and others/property. This thread is being closed for the same reason. Please do not start another.