Transformerless Power Supply

[kadunk]

First i got to thank all who helped me out with the 7 segment LED counter. I made it and it was my first project ever. So far loving Electronics.

I found another project mentioned in the topic but before i start i would like to know what each component does. And don't worry I know the dangers in making this and im well aware.

basically this is the circuit https://www.aaroncake.net/circuits/supply5.asp
just wonder what each component acts in this circuit like

Capacitor
Electrolytic Capacitor
Zener Diode
Bridge Rectifier

if someone could help me out and describe what each component does in this circuit.
And I was also wondering why doesn't this circuit have resistors?

Thanks in advance,

 

[kchriste]

Capacitor
C1 drops the incoming AC voltage via capacitive reactance. Basically it does the job of a dropping resistor without the heat.
Electrolytic Capacitor
Smooths the pulsating DC from the bridge rectifier.
Zener Diode
Regulates the output voltage.
Bridge Rectifier
Turns AC into pulsating DC.

And I was also wondering why doesn't this circuit have resistors?

It really should have a small value resistor ( Say 220hm in series with C1 to guard against inrush current damaging the bridge rectifier.

 

[ericgibbs]

hi kadunk,
The psu is NOT isolated from the mains supply and I would recommend that you dont build it.
They are mainly used in enclosed devices where the 'user' cannot come into contact with any part of the wiring.

If you ever plugged it into an incorrectly wired mains socket, ie reveresed wired, the psu and the circuit
its powering would be at the mains potential

Buy a simple 'wall wart' , with an output voltage of say +15V, 1A and use two regulators on your board
to give +12Vdc and +5Vdc, it much safer to have the mains isolating transformer.