hello ,
i am in the process of making an AC dimmer circuit , the problem i encountered is that the zero cross detection section isnt working , it works well on isis proteus but in practical it only shows a a direct voltage of 1v in the oscilloscope .
here is the schematic and the result that it shows :
any help would be great, we're out of ideas.
best regards,
Hi,
Why are you using a sine AC supply voltage on the output of the 4N35?
It should be a DC voltage suitable for the controller to have as its input.
This might help.
Tom.. 
thank you TOM , i tried it and it worked . it now gives me a square signal wich i can use in my program with attachinterrupt(0,zerocross,CHANGE).
Never mind, you happy, I'm happy.
Could you back out bit and show a complete schematic?
This is the kind of thing I see when I google to learn more:
TIA
a7
this is the same schematic i work with now just the value of the resistance in the left is 1k ohm
Can't see which pins U1 and U2 are connected to.
Please post a screen capture of the entire circuit or a pdf
volatile int dimming = 128;
attachInterrupt(0,acon,CHANGE); waits for interrupt on pin 2 on Uno/Nano/Mini.
are you sure you want a go high, then stay low pulse?
Also, you should use RISING on interrupt, change will trigger it twice.
the signal the zero cross gives me is square so i used change to have itriggered twice with every rising and falling edge
yes the triac only needs a small pulse until the next zero is detected
Your code outputs the pulse on pin 3 but you have the TRIAC connected to pin 8
Please post an image that shows the entire schematic
yes that was a mistake on my part i did change the code to pin 8 but forgot to change it in the code . i now re examined both and put it on 3
So is there now a signal on pin 3?
I guess you have a "square" pulse of <1ms of length. Why would you want to trigger it twice?
The reverse voltage on that 4N35 emitter is pretty low.
i am using an oscilloscope to display the signal from pin 3 but it shows nothing . the zero cross signal is delivered without a problem
beacause every edge signals a zero cross
does that mean i should decrease the value of the resistance ?
