Current through Capacitor connected with 220VAC - Page 1
Forum section: electronics / beginners

author: MMDuino
author_rank: Regular Contributor
timestamp: April 21, 2015, 06:31:14 am
content: Dear AllHow can i know the current output of the Capacitors connected with AC 220 V? please see attached diagram and reply if there is mistakes or there is a design better than what i attached.

author: Psi
author_rank: Super Contributor
timestamp: April 21, 2015, 06:42:46 am
content: You need to calculate the reactance of the capacitor (Xc).Basically this gets you a resistance in ohms that the cap will "appear" to be at a given frequency and capacity.Xc = 1/ 2 * pi * f * csoAssuming your mains is 50hz and your 486 cap is 48uf1/ (2x 3.14 * 50Hz * 0.000048F)Xc = 66 ohms220V / 66 ohms = ISo the max current though that cap is 3.33A

author: PSR B1257
author_rank: Frequent Contributor
timestamp: April 21, 2015, 06:46:21 am
content: That circuit did not work at all.What are you looking for?And I'm not sure what you mean byQuoteThere is nocurrent outputat a capacitor.The way you have connected the diodes results in a direct current. And therefor not current is flowing at all.

author: Psi
author_rank: Super Contributor
timestamp: April 21, 2015, 06:48:15 am
content: PSR B1257 raises a good point

author: Simon
author_rank: Unknown
timestamp: April 21, 2015, 06:49:07 am
content: Quote from: Psi on April 21, 2015, 06:42:46 amGee let the guy do "some" of his own homework

author: MMDuino
author_rank: Regular Contributor
timestamp: April 21, 2015, 06:54:27 am
content: Thank you very much PsiI want to use this circuit to operate timer (by using LM339) & Relay 24V - 0.040 Amp, finally when i built this circuit and connect 2 relays, the current was not enough to switch on the 2 relays, so do you advice me to use 2 capacitors connected in parallel to increase the current?Quote from: Psi on April 21, 2015, 06:42:46 am

author: PSR B1257
author_rank: Frequent Contributor
timestamp: April 21, 2015, 07:00:55 am
content: Do your self a favor and and use a transformer.What you are trying to build is obviously ahttp://en.wikipedia.org/wiki/Capacitive_power_supplycapacitive power supply. But these supplies are only safe, if you are aware of what you are doing.

author: Psi
author_rank: Super Contributor
timestamp: April 21, 2015, 07:03:16 am
content: As others have said, your circuit isn't correct. And the type of powersupply you're building isnotfor beginners. Even experienced engineers usually stay away from those things.I also question if you cap really is 486 (48uf).A 48uf 220VAC cap would be the size of a large coffee cup.

author: MMDuino
author_rank: Regular Contributor
timestamp: April 21, 2015, 07:06:52 am
content: I can't use a transformer for 2 reasons the space inside the plastic box is not enough and if use a transformer the total cost will change the idea of my project.Quote from: PSR B1257 on April 21, 2015, 07:00:55 am

author: MMDuino
author_rank: Regular Contributor
timestamp: April 21, 2015, 07:09:09 am
content: Really i'm very sorry for my mistake,,, it's not 486,,,,it's 684......it's small ceramic capacitor...Quote from: Psi on April 21, 2015, 07:03:16 am

author: Psi
author_rank: Super Contributor
timestamp: April 21, 2015, 07:10:36 am
content: It's unlikely you have a ceramic cap which is rated for mains.The cap needs to be a X2 rated mains film capacitor.

author: MMDuino
author_rank: Regular Contributor
timestamp: April 21, 2015, 07:15:27 am
content: i used this one...Quote from: Psi on April 21, 2015, 07:10:36 am

author: Psi
author_rank: Super Contributor
timestamp: April 21, 2015, 07:16:58 am
content: That most likelyisa film cap, but it's only rated from 250V DC not 220V AC which is ~315VDC.And it's not X2 rated.

author: MMDuino
author_rank: Regular Contributor
timestamp: April 21, 2015, 07:30:03 am
content: Dear PSimy circuit its works well with 1 relay (one trip), my idea to use same circuit (unused comparator of LM324 or LM339) with CT + Relay (my circuit it will be timer, under/overVoltage and overload protection with 220vAc 50Hz).Quote from: Psi on April 21, 2015, 07:16:58 am

author: MMDuino
author_rank: Regular Contributor
timestamp: April 21, 2015, 08:04:39 am
content: Dear PSiMy idea in future is to use PIC16F690, but i'm still under beginner with microcontrollers...

author: Zero999
author_rank: Super Contributor
timestamp: April 21, 2015, 08:20:48 am
content: You wrote the capacitor code incorrectly on your schematic. 684 is 680nF.It isn't unusual for capacitors designed to operate off AC to be marked with the RMS voltage rating, another possibility is it's just junk and they've undersized the parts.Where did you get this circuit board from? It's not very good quality.There should also be a zener diode or other kind of shunt regulator in parallel with the 1000µF capacitor, otherwise the voltage will exceed its maximum rating, causing it to explode.

author: MMDuino
author_rank: Regular Contributor
timestamp: April 21, 2015, 08:27:51 am
content: Dear Hero 999Please read all comments ,, then you will get my point...Quote from: Hero999 on April 21, 2015, 08:20:48 am

author: Zero999
author_rank: Super Contributor
timestamp: April 21, 2015, 09:03:48 am
content: I did read all of your comments and you've not said anything about where you got the circuit from or a complete schematic.

author: Zero999
author_rank: Super Contributor
timestamp: April 21, 2015, 09:08:56 am
content: Quote from: blueskull on April 21, 2015, 09:06:44 amI agree but whether he'll listen or not is another thing.

author: MMDuino
author_rank: Regular Contributor
timestamp: April 21, 2015, 09:10:53 am
content: its not big idea Hero, it's only LM339, 4 comparators , use 1/4 - under voltage comparator, 2/4 - over voltage , 3/4 - timer, 4/4 - overload,,but i used the Capacitor as a power source cause it's cheaper and smaller than the transformer..thats it...Quote from: Hero999 on April 21, 2015, 09:03:48 am

author: Zero999
author_rank: Super Contributor
timestamp: April 21, 2015, 09:17:18 am
content: Quote from: MMDuino on April 21, 2015, 09:10:53 amWhat regulates/limits the voltage across the 1000µF capacitor?

author: MMDuino
author_rank: Regular Contributor
timestamp: April 21, 2015, 09:35:06 am
content: Please see what i built...Quote from: Hero999 on April 21, 2015, 09:17:18 am

author: PSR B1257
author_rank: Frequent Contributor
timestamp: April 21, 2015, 09:49:52 am
content: Oh dear...That's a whole nother story. This circuit works since there is a resistor across the capacitor.

author: matseng
author_rank: Frequent Contributor
timestamp: April 21, 2015, 10:03:50 am
content: Quote from: Hero999 on April 21, 2015, 08:20:48 amIt seems like even big brands like Panasonic are using crap parts or marginal specs. I have replaced the 'dropping caps' for the transformerless powersupplies on the control board in 8 out of my 9 Panasonic ceiling fans. They lasted between three to four years before they gave up the ghost. The first I replaced is soon coming up on its third birthday, so maybe they will start dying again soon. :-)

author: Zero999
author_rank: Super Contributor
timestamp: April 21, 2015, 12:03:34 pm
content: Quote from: MMDuino on April 21, 2015, 09:35:06 amThe 0.68uF capacitor doesn't do anything but charge up, since it has two diodes in series with it, so the current will be limited by the 560k resistor.I suspect you've drawn the bottom diode in the wrong place.Read the documents linked to below for information on how to properly design transformerless power supplies:http://ww1.microchip.com/downloads/en/AppNotes/00954A.pdfhttp://www.designercircuits.com/DesignNote1a.pdf

author: MMDuino
author_rank: Regular Contributor
timestamp: April 21, 2015, 12:21:05 pm
content: Thanks Hero999It's very helpful PDFs..Quote from: Hero999 on April 21, 2015, 12:03:34 pm

author: matseng
author_rank: Frequent Contributor
timestamp: April 21, 2015, 12:53:06 pm
content: Here's a nice online calculator for determining the max current and power losses in some different types of transformerless PSUs.http://www.daycounter.com/Circuits/Transformerless-Power-Supplies/Transformerless-Power-Supplies.phtml

author: MMDuino
author_rank: Regular Contributor
timestamp: April 21, 2015, 01:04:23 pm
content: Ohh, it is very good site,Thank you very much matseng..Quote from: matseng on April 21, 2015, 12:53:06 pm

author: macboy
author_rank: Super Contributor
timestamp: April 21, 2015, 05:05:16 pm
content: Quote from: MMDuino on April 21, 2015, 07:15:27 amI predict a new Darwin award winner.