Optically Isolated Phase Controlling Circuit

[dhanush]

I got a schemetic from fairchild for Optically Isolated Phase Controlling. I modified a little bit on that schemetic before the Optoisolator. Please check my schemetic and reply any problem on my modified schemetic.

I attached both schemetic, one is from fairchild and the other one I modified.

[Melanie]

In your version, what is the point of the H11L1 opto?

[dhanush]

In your version, what is the point of the H11L1 opto?

I cant understant what u r asking. Point means? Please explain your question.

I am going to develop this circuit for fan regulator and it is not for one, i want to attach upto 25 fan regulator by adding same circuit (after optoisolator) again. So i am scare about lightning, thats why i am using optoisolator with transformer (not directly connect to main supply). This project is developing for large office purpuse.

And please mention, what transistor I need to use for trigering upto 25 LM555 IC, instead of MPSA40. Is MPSA40 have enough current for trigger pin of LM555, if I attach 25 LM555. I am not an expert please help.

[aratti]

In the first schematic H11L1 trigger LM555 at every zero crossing, in the second schematic H11L1 is on all the time (so it is useless). Second schematic will not work!

Zero crossing happens when the sin wave of your main, cross the zero line.

Al.

[dhanush]

In the first schematic H11L1 trigger LM555 at every zero crossing, in the second schematic H11L1 is on all the time (so it is useless). Second schematic will not work!

Zero crossing happens when the sin wave of your main, cross the zero line.

Al.

What is the problem on second schemetic? Please resolve the problem on second schemetic, I dont need to connect directly on main, I need to connect via transformer, please help me.

I have an another circuit that was published on EFY Magazine, that circuit is connected via transformer, I will give you that pdf link http://www.electronicsforu.com/EFYLi...-01_July06.pdf and recorrect my error on second schemetic. I need to work second schemetic same like newly given schemetic. Please resolve it.

Thanks for reporting the error.

[Melanie]

Actually my point was that in the first schematic the H11L1 is providing isolation from the supply to the 555, in the second it is provided by the Transformer - which makes it kind of pointless having it still in circuit. Also that Transformer is 12-0-12... is there a reason you want to run your Trigger circuit at 24v?

Blindly copying other peoples schematics is one thing... but modifying them without actually knowing what they do is another (kinda like all the cut & paste that goes on in this forum I suppose)...

[dhanush]

Actually my point was that in the first schematic the H11L1 is providing isolation from the supply to the 555, in the second it is provided by the Transformer - which makes it kind of pointless having it still in circuit. Also that Transformer is 12-0-12... is there a reason you want to run your Trigger circuit at 24v?

Blindly copying other peoples schematics is one thing... but modifying them without actually knowing what they do is another (kinda like all the cut & paste that goes on in this forum I suppose)...

I am developing a remote control system using microcontroller, my project is not only control fan regulators, its also control lamps etc. So I add more than 10 relays for switching lamps. My all relays are using 12v. So the 12volt transformer is using for other purpose also like relays etc not only for above mentioned schemetic.

[aratti]

Try this way it should work.

Than place an oscilloscope on pin 2 of LM555 and you should see a pulse every 8,3 milliseconds (if your main is 60 Hz) or every 10 milliseconds ( if your main is 50 Hz)

Al.

[dhanush]

Try this way it should work.

Than place an oscilloscope on pin 2 of LM555 and you should see a pulse every 8,3 milliseconds (if your main is 60 Hz) or every 10 milliseconds ( if your main is 50 Hz)

Al.

Thank you so much aratti.

Ok I am going to build with your way, but I like know that what are the problems in my circuit, you said H11L1 is on all time, so zero crossing detecter should not work. When I am looking your way, the main differents is you are not avoiding zener diode (D5) and H11L1 parallel resistor (R2) right? On EFY Magazine circuit both components are not using, but that is working circuit. For getting knowlege, can you please explain why zener diode (D5) and resistor (R2) is used in this circuit?

And also please tell me, if I want trigger upto twenty five LM555 for controlling upto 25 fan, which transistor I need to use instead of MPSA40. Is this transistor has enough current to trigger upto 25 LM555?

[aratti]

For getting knowlege, can you please explain why zener diode (D5) and resistor (R2) is used in this circuit?

Detecting the zerocrossing correctly (without delay) is not a simple metter. Here we have got to thrust Fairchild engineers.

When you have got a working circuit, with the proper zerocrossing pulse detected by your oscilloscope, then tray to remove some components you judge useless and see the result on your scope. If pattern doesn't change you were right otherwise you will have to resolder the component in its original position.

This is the best way to learn.

And also please tell me, if I want trigger upto twenty five LM555 for controlling upto 25 fan, which transistor I need to use instead of MPSA40. Is this transistor has enough current to trigger upto 25 LM555?

I don't recommend to use this solution having a long wire connected to pin 2 of LM555 will works as an antenna with unpredictable results.

You should have 25 complete circuits, you can supply the 12 Vac directly to all 25.



Al

[dhanush]

Detecting the zerocrossing correctly (without delay) is not a simple metter. Here we have got to thrust Fairchild engineers.

When you have got a working circuit, with the proper zerocrossing pulse detected by your oscilloscope, then tray to remove some components you judge useless and see the result on your scope. If pattern doesn't change you were right otherwise you will have to resolder the component in its original position.

This is the best way to learn.

Al

I am not trusting EFY Magazine schemetic that why I am using Fairchild schemetic. EFY Mag is Indian edition. I am developing this project is for business purpose, so I need quality product. Good reply and thanks.