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IC that detects the zero cross directly from the ac line 85~265

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veioloko

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hello
does anybody know an ic that detects the zero cross directly from the ac line 85~265?
without transformer? because i don´t want to use transformer and neither big resistors.
i wan´t to do a digital dimmer.
thanks and sorry for my english
 

zero crossing moc

Not sure if there are discrete ICs that operates in the voltage range that you want.
National Semiconductor's LM1815 allows you to operate upto 120V using external resistors.
 

why we use fuse

thanks but i don´t want to use moc....i just want to detect the zero cross and pick a low or high digital signal, that the microcontroler will use.
does anyone knows how is the circuit that is inside moc? that detects the zero?
 

zero crossing 110 220v

Hi Veioloko,

What about a discrete solution ? The width of the output pulse is
200 µS, the steep trailing edge is the reference.
Be careful, it could be a shocking experience! :D

on1aag.
 

zero cross detect optocouplers

you can detect zero crossing using amplifiers connect (-)pin to ground and the(+) to the signal u want when the wave be zero as ground the output will be zero other will give -VCC or +VCC as the signal move in the negative part or possitive one
 

Re: Zero crossing

HV Zero crossing detection is almost always done with simple optcoupler circuits and then maybe some other passives to tailor the waveform to your needs.

Please see the picture for a simple example of how to do crossover detection with very few components.

Hope it helps
 

Re: Zero crossing

Hello
thanks but i´m using a full wave rectifier.....
The ideia that you give is good becuase it use only a half..consequently less power....
However the power in both circuits are very high...
I made a circuit using the 6n139 that requires only 1mA at imput...so i could turn the circuit in 110 and 220. But i used two 22k 7w in series. I get +- 40ºC ....
How can i reduce the size of the circuit and the heating?
I want a 120hz signal in the microcontroler....
 
Re: Zero crossing

BigBenG said:
HV Zero crossing detection is almost always done with simple optcoupler circuits and then maybe some other passives to tailor the waveform to your needs.

Please see the picture for a simple example of how to do crossover detection with very few components.

Hope it helps
Click to expand...


Can you explain me how this circuit works? I didn't understand why we use fuse and another devices. there is anyone to help me in this subject? Thanks so much.


8)
 

Re: Zero crossing

The circuit is simple to understand

The fuse is there only for security.
Resistors are used to "limit" the voltage in the optocoupler.
When we have less than +-1.2v,the optocoupler will not work, so we have the zero cross
 

Re: Zero crossing

BigBenG said:
HV Zero crossing detection is almost always done with simple optcoupler circuits and then maybe some other passives to tailor the waveform to your needs.

Please see the picture for a simple example of how to do crossover detection with very few components.

Hope it helps
Click to expand...

but the diode reverse-peak voltage is about 3V.so 220 ac damages the opto-coupler.Am I wrong?does the circuit in the picture work?
 

Re: Zero crossing

Just use a high value resistor, something like 4M7 and feed it into one of your micro input ports. Use clamping diodes to supply and ground on the input pin.
 
Re: Zero crossing

btbass said:
Just use a high value resistor, something like 4M7 and feed it into one of your micro input ports. Use clamping diodes to supply and ground on the input pin.
Click to expand...

secondly a normal opto-transistör input current 60-80 mA.if 120 K resistor is used
then opt-coupler input current will be very low to operate opt-coupler.(120K resistor in picture ).for example at 22v ac voltage level,about 300 ohm resistor must be used for acquiring 60-80 mA.But at peak level (220 volt ) this resitor will be too low.Consequently there is a dilemma.

I think the curcuit in the picture is not a good idea.Do you agree?If not why?
 
Re: Zero crossing

btbass said:
Just use a high value resistor, something like 4M7 and feed it into one of your micro input ports. Use clamping diodes to supply and ground on the input pin.
Click to expand...

How does that work with 60Hz slow moving waveforms? Is it possible to detect just the falling edge zero cross?

I’ve read of doing it using the internal ESD diodes in PIC’s never tried it yet though.

If I get sometime this weekend I'll try it on a low voltage AC.
 
Re: Zero crossing

max0412 said:
btbass said:
Just use a high value resistor, something like 4M7 and feed it into one of your micro input ports. Use clamping diodes to supply and ground on the input pin.
Click to expand...

How does that work with 60Hz slow moving waveforms? Is it possible to detect just the falling edge zero cross?

I’ve read of doing it using the internal ESD diodes in PIC’s never tried it yet though.

If I get sometime this weekend I'll try it on a low voltage AC.
Click to expand...

of course resolution will be low.because 220v volt will be reduced 5,1 v.
at low level ac it can ce useful.A/D of pic should be used.under zero level detection can not be done without op-amp curcuit or etc.
 

Re: Zero crossing

If the pic is supplied by a rectified ground ref. from a single supply, the ac swings above and below this. The input is just pulled high and low on the crossings and clamped by the diodes.
A dimmer is a hot circuit anyway, just be careful, make sure the whole thing is isolated!
 

Zero crossing

u can use opamp in open loop configuration for zero crossing
 

Re: Zero crossing

Here is some example. GP3 is the input for sensing zero crossing.You can use the part connected to it for your project.Or the whole project.Have fun:D
 

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