Close or Esc Key

Arduino Projects   |   Raspberry Pi   |   Electronic Circuits   |   AVR   |   PIC   |   8051   |   Electronic Projects

Smart Capacitor power supply



Thank you for your valuable information.

i expect more isolation in this case . that is this is tfr less supply . But why we give a small tfr use here at low cost that is i think input voltage is if less than 100V b/w the capacitor after droping the voltage across the it.

Pls . give me your valuable suggestion .....


Shibu AS

Pachalam. Ernakulam

what is the rating of capacitor ?

also please tell how to convert it to 5 v power supply ?

Hi, the above cap has a value 225. This means (2200000/1000000) ?F or 2.2 ?F. For 5v low current transformerless power supply, simply built a circuit using a 474k x rated cap with voltage rating 400v. Then use a 7805 ic to get a regulated 5v output. I have built a couple of transformerless powersupplies. You can have a look at ]]>]]> For any queries, doubts please feel free to mail me at

1.what is a smart capacitor? 

what are its applications?

please explain its working?


2.Please explain how MOSFET can be used as a switch.

Thank you for you work


I have some issues i will be appriciated if you kindly help with


1- What is the Bridge Ractifier output voltage ,is it calculated based on the following equation:


Vout = Vpk X 0.637 = Vrms X 1.414 X 0.637 or Vout = Vrms X 0.9 where Vrms = 230/3 = 115 thus

output voltage of the bridge = 115 X 0.9 = 103.5V where you said


voltage rating of the smoothing capacitor should be three times higher than that of the rectified voltage. Here 60 volt capacitor is used. Smoothing of DC which mean the ractified voltage = 60/3 = 20V how we get this voltage, I understand that this related to the capacitance property for C1 and C2 how this value calulated.


2-how we calculate the value of R3


sorry for any inconvinince but i am new in this aspect and i am just a hobbiyst and there is no good information regarding this type of circuits on the web.



Dear Mr. Mohankumar,


It may mislead readers to suggest that the capacitor supply with series caps in both line and neutral is safe.  Although the dual capacitors provide DC isolation, they do not provide AC isolation.  The AC neutral line is typically at earth-ground potential; a grounded user touching the supply output will receive as much current as the supply can deliver.  By contrast, a grounded user touching the output of a galvanically isolated (transformer) supply would be safe and would receive no current.

If I have misunderstood, please correct me; either way, thank you for the interesting articles, I've read several of your posts and enjoyed them immensely.



thank u sir,

can i use two x rated capacitor in paralell to increase the output current

Yes, two parallel capacitors will increase the output current.

Can we provide isolation from ac supply in capacitor based supply. I mean get rid of electric shock.

sir i connected this circuit but i getting one problem that in the circuit we have provided one indicator light for main supply to indicate whether charge is getting or not but my problem is after connecting battery that led is continuous glowing. what to do

i have tried this circuit for one application but facing zener diode heating problem please help.,

please use zener is higher wattage such as 12v 3watt

Sir how to calculate output voltage available across filter capacitor (ie output) and how to calculate voltage available across bridge rectifier input. 


As David Albert already pointed out, this circuit is *not* to be considered isolated. It should never be constructed so that a person may touch the "low voltage"end of the circuit, since each of the capacitors can pass a lethal amount of AC current.