EEVblog Electronics Community Forum
Electronics => Beginners => Topic started by: MMDuino on April 21, 2015, 06:31:14 am
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Dear All
How 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.
(http://i61.tinypic.com/243566w.jpg)
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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 * c
so
Assuming your mains is 50hz and your 486 cap is 48uf
1/ (2x 3.14 * 50Hz * 0.000048F)
Xc = 66 ohms
220V / 66 ohms = I
So the max current though that cap is 3.33A
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That circuit did not work at all.
What are you looking for?
And I'm not sure what you mean by the current output of the Capacitors connected with AC 220 V?
There is no current output at a capacitor.
The way you have connected the diodes results in a direct current. And therefor not current is flowing at all.
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PSR B1257 raises a good point
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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 * c
so
Assuming your mains is 50hz and your 486 cap is 48uf
1/ (2x 3.14 * 50Hz * 0.000048F)
Xc = 66 ohms
220V / 66 ohms = I
So the max current though that cap is 3.33A
Gee let the guy do "some" of his own homework ;)
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Thank you very much Psi
I 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?
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 * c
so
Assuming your mains is 50hz and your 486 cap is 48uf
1/ (2x 3.14 * 50Hz * 0.000048F)
Xc = 66 ohms
220V / 66 ohms = I
So the max current though that cap is 3.33A
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Do your self a favor and and use a transformer.
What you are trying to build is obviously a http://en.wikipedia.org/wiki/Capacitive_power_supply (http://en.wikipedia.org/wiki/Capacitive_power_supply) capacitive power supply. But these supplies are only safe, if you are aware of what you are doing.
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As others have said, your circuit isn't correct. And the type of powersupply you're building is not for 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.
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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.
Do your self a favor and and use a transformer.
What you are trying to build is obviously a http://en.wikipedia.org/wiki/Capacitive_power_supply (http://en.wikipedia.org/wiki/Capacitive_power_supply) capacitive power supply. But these supplies are only safe, if you are aware of what you are doing.
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Really i'm very sorry for my mistake,,, it's not 486,,,,it's 684......it's small ceramic capacitor...
As others have said, your circuit isn't correct. And the type of powersupply you're building is not for 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.
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It's unlikely you have a ceramic cap which is rated for mains.
The cap needs to be a X2 rated mains film capacitor.
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i used this one...
(http://i57.tinypic.com/eia2w6.jpg)
You cannot use a ceramic cap.
It has to be a X2 rated film capacitor
https://www.google.co.nz/search?q=X2+film+capacitor (https://www.google.co.nz/search?q=X2+film+capacitor)
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That most likely is a film cap, but it's only rated from 250V DC not 220V AC which is ~315VDC.
And it's not X2 rated.
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Dear PSi
my 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).
(http://i58.tinypic.com/2d793k3.jpg)
That most likely is a film cap, but it's only rated from 250V DC not 220V AC which is ~315VDC.
And it's not X2 rated.
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Dear PSi
My idea in future is to use PIC16F690 ;), but i'm still under beginner with microcontrollers |O |O...
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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.
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Dear Hero 999
Please read all comments ,, then you will get my point...
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.
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I did read all of your comments and you've not said anything about where you got the circuit from or a complete schematic.
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Before this guy knows what he is doing and fully understand it, let's NOT teaching him how to kill himself. A capacitive divider can easily kill if not used properly, and even used properly, inadequate loading can still results in excessive voltage, and even everything works well, you can be zapped by the residual charge.
Before knowing what you are doing, go get a xfmr is a better choice.
I agree but whether he'll listen or not is another thing.
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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...
I did read all of your comments and you've not said anything about where you got the circuit from or a complete schematic.
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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...
What regulates/limits the voltage across the 1000µF capacitor?
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Please see what i built...
(http://i62.tinypic.com/27y936f.jpg)
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...
What regulates/limits the voltage across the 1000µF capacitor?
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Oh dear...That's a whole nother story. This circuit works since there is a resistor across the capacitor.
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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.
It 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. :-)
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Please see what i built...
(http://i62.tinypic.com/27y936f.jpg)
The 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.pdf (http://ww1.microchip.com/downloads/en/AppNotes/00954A.pdf)
http://www.designercircuits.com/DesignNote1a.pdf (http://www.designercircuits.com/DesignNote1a.pdf)
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Thanks Hero999
It's very helpful PDFs..
Please see what i built...
(http://i62.tinypic.com/27y936f.jpg)
The 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.pdf (http://ww1.microchip.com/downloads/en/AppNotes/00954A.pdf)
http://www.designercircuits.com/DesignNote1a.pdf (http://www.designercircuits.com/DesignNote1a.pdf)
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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 (http://www.daycounter.com/Circuits/Transformerless-Power-Supplies/Transformerless-Power-Supplies.phtml)
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Ohh, it is very good site, :clap:
Thank you very much matseng..
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 (http://www.daycounter.com/Circuits/Transformerless-Power-Supplies/Transformerless-Power-Supplies.phtml)
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i used this one...
(http://i57.tinypic.com/eia2w6.jpg)
You cannot use a ceramic cap.
It has to be a X2 rated film capacitor
https://www.google.co.nz/search?q=X2+film+capacitor (https://www.google.co.nz/search?q=X2+film+capacitor)
:palm:
I predict a new Darwin award winner.