Welcome to EDAboard.com

Welcome to our site! EDAboard.com is an international Electronics Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.

Circuit for detecting the zero-crossing of a 240V line

Status
Not open for further replies.

ZeleC

Full Member level 5
Joined
Dec 18, 2002
Messages
261
Helped
3
Reputation
6
Reaction score
1
Trophy points
1,298
Activity points
2,173
i m searching for an easy and efficient circuit to detect the zero-crossing of a 240V line so that it can be feed to a microcontroller(i want to control a thyristor)
any help from yu guys will be great
thanks
 

cozturk

Advanced Member level 4
Joined
Apr 2, 2002
Messages
105
Helped
3
Reputation
6
Reaction score
3
Trophy points
1,298
Activity points
904
application note zero crossing detector microchip

You need only 3meg resistor to mcu pin which used in pic12c508 non-isolated dimmer project. Look this.
**broken link removed**
 

papyaki

Advanced Member level 2
Joined
Apr 13, 2002
Messages
539
Helped
38
Reputation
76
Reaction score
18
Trophy points
1,298
Location
France
Activity points
5,346
hcpl3700 240v

Hi,

Look at HCPL-3700 optocoupler : h**p://www.fairchildsemi.com/ds/HC/HCPL-3700.pdf

look also this topic : h**p://

* = t
 

Henrico

Member level 2
Joined
Aug 25, 2004
Messages
45
Helped
1
Reputation
2
Reaction score
0
Trophy points
1,286
Activity points
398
240v isolated zero cross detection

ZeleC said:
i m searching for an easy and efficient circuit to detect the zero-crossing of a 240V line so that it can be feed to a microcontroller(i want to control a thyristor)
any help from yu guys will be great
thanks

Google for MOC 3041 (Motorola).Single chip solution with built in Z/Crossing detection.
 

ZeleC

Full Member level 5
Joined
Dec 18, 2002
Messages
261
Helped
3
Reputation
6
Reaction score
1
Trophy points
1,298
Activity points
2,173
hcpl3700 zero crossing

hello
my main object was to transform the sin wave of a ac line phase to a microcontroller in other words when the i have positive it will be logic 1 and when the phase is negative it will be 0 logic , so that i would have a square wave with a freq as same as the AC line (50Hz) coming to the microcontroller , im not seeing a way of doing that with the above ICs
thx you
 

Taro

Full Member level 2
Joined
Jun 28, 2001
Messages
143
Helped
8
Reputation
16
Reaction score
5
Trophy points
1,298
Activity points
1,195
mains zero crossing schmitt

Dear Zelec
You can make Zero crossing detection many in ways, such as Optoisolate that include Zero-crossing output pin, use NPN transistor get un-filtered signal that come from bridge rectified, etc. But in my opinion I think cozturk's idea is suitable for your demand.

BTW you have to know before that inside PIC'port structure they have diode clamp up to +Vcc and clamp down with GND, so your PIC port is not demaged by 220V voltage. So before use this method, be careful to check your port structure of your microntroller.

Hope it can help
TARO :)
 
  • Like
Reactions: atheer

    atheer

    Points: 2
    Helpful Answer Positive Rating

seven_segment

Member level 2
Joined
Aug 23, 2004
Messages
44
Helped
0
Reputation
0
Reaction score
0
Trophy points
1,286
Activity points
540
mains zero crossing diode

Using an OptoCoupler would probably be the easiest (and safest) solution. Simply keep polling one of your input pins, when the state of the input is reversed (ie logic 1 to 0, or vice versa) you know that zero crossing has just occured. This should be accurate enough, I've done dimming this way without problems.
 

amraldo

Advanced Member level 4
Joined
Aug 29, 2004
Messages
1,185
Helped
145
Reputation
290
Reaction score
40
Trophy points
1,328
Location
Egypt
Activity points
5,880
signal zero crossing detector +microchip

here is a suggestion and it might work:
1-u have to step down the voltage level to an acceptable one (say 5V)
2-use a comparator circuit configuring opamps to produce the logic levels u want.
3-choose the supplies of the comparator propely to produce the required voltage levels representing ur logic levels
 

ZeleC

Full Member level 5
Joined
Dec 18, 2002
Messages
261
Helped
3
Reputation
6
Reaction score
1
Trophy points
1,298
Activity points
2,173
moc3041motorola

pic is a good idea
but currently im using hc11,
i tried to used a transformer to step down , and then used a couple of buterworth filters and a comparator at the end its working but im having a small problem , the line signal and the one that i got after the comparator are not in phase (~pi/6 difference and not stable sometimes less sometimes greater) a part of this is getting from the transformer some from the filters.
And that is not suitable to control the thyristor because its not the same image as the main line input.
 

metal

Full Member level 6
Joined
Dec 21, 2004
Messages
364
Helped
19
Reputation
38
Reaction score
6
Trophy points
1,298
Activity points
3,834
zero crossing detection pic

Hello

You can use schmitt-trigger gate to generate clock signals, as long as mains insulation is not important.

A resistor has to be used to reduce the mains voltage.

Anothre thing onmind, search motorola App. Notes, I have downloaded long time ago, it uses logic gate opto-coupler.

Regards
 

VVV

Advanced Member level 5
Joined
Nov 26, 2004
Messages
1,582
Helped
384
Reputation
768
Reaction score
88
Trophy points
1,328
Activity points
19,971
microchip zerocrossing

I used the voltage from the transformer and fed it directly to a PIC, through a resistor. The PIC input diodes clamp the voltage, the current is limited by the resistor. Got the idea from Microchip's AN521: ww1.microchip.com/downloads/en/AppNotes/00521c.pdf Although, as I said, I did not connect to the AC line directly, but through a 12Vac transformer and a 47K resistor.
Then I wrote a short adjustable delay routine. With that I was able to predict accurately the next zero-crossing. It worked much like a PLL.
 

lojz100

Junior Member level 1
Joined
Feb 12, 2002
Messages
17
Helped
0
Reputation
0
Reaction score
0
Trophy points
1,281
Activity points
55
zero crossing microchip

I use this and it works fine

:spoko:
 

Status
Not open for further replies.

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Top