MOC3041

[zika1212]

what is the function of the zero-crossing in the MOC3041 and what it is its effect on the AC signal ?? and what is the name of the part that is similar to MOC3041 but without zero-crossing ??

 

[Sebi]

Firing a triac (or SCR in AC circuit) nearby the sinus zerocross is a good idea to avoid high switching transients. MOC3021 not contain zerocross circuit.

 

[sivankls]

How to know the MOC3041 switches @ Zerocross ?

 

[Hero999]

Yes, the MOC3041 contains a zero crossing unit; what's your question?

 

[Papabravo]

How to know the MOC3041 switches @ Zerocross ?

You look at the datasheet.

 

[sivankls]

how to know that the triac fired thru MOC3041 is @ zero crossing of mains ? I have a pulse charger switching circuit, which makes thumb like sound when the triac fires..have a feeling that the MOC is not working properly or is it because of inductive load...any suggestions to make it soft switch ? Thanks in advance..

 

[Nigel Goodwin]

how to know that the triac fired thru MOC3041 is @ zero crossing of mains ? I have a pulse charger switching circuit, which makes thumb like sound when the triac fires..have a feeling that the MOC is not working properly or is it because of inductive load...any suggestions to make it soft switch ? Thanks in advance..

Check with a scope to see where it's firing - however if you've wired it correctly it WILL be zero switching!.

What is the load you're switching?.

 

[sivankls]

Thanks Nigel Goodwin
The load is the primary of a 300 Watts power transformer the secondary is bridge rectified and fed to a battery.
Please find the circuit...attached..
The problem is the site that i work doesn't have access to a Oscilloscope..

 

[Nigel Goodwin]

A 300W transformer will 'thump' as it turns on, even at zero-crossing.

 

[sivankls]

how ? I don't understand...If voltage is near zero..and current follows the same..how come the "Thumb"...high current occurring ?
Then whatz the use of Zero cross-witching ?

 

[Nigel Goodwin]

how ? I don't understand...If voltage is near zero..and current follows the same..how come the "Thumb"...high current occurring ?
Then whatz the use of Zero cross-witching ?

The 'thump' occurs as the mains voltage rapidly increases from zero to peak - with out zero-crossing switching it may instantly have full peak mains across it, resulting in a MUCH greater thump, and a massively greater mains surge.

It also prevents high levels of mains interference being generated every time it switches.

To prevent the thump altogether you need a soft-start system.

 

[sivankls]

The 'thump' occurs as the mains voltage rapidly increases from zero to peak

..If thats the case...this thumb will occur when ever the mains wave form cross zero to Peak !!

 

[Nigel Goodwin]

..If thats the case...this thumb will occur when ever the mains wave form cross zero to Peak !!

No, because it's 'buzzing' all the time then, as the AC swings from negative to positive and back - it's the sudden new surge of current that makes the 'thump', with the core not already magnetised.

 

[sivankls]

Ok..thanks for ur replies,,,,BY the way did u see the circuit i posted ? can we replace CD4060 & 555 with a dual 555 ie 556 ?

 

[Nigel Goodwin]

No, the CD4060 is there to give a MUCH longer time than a 555 can manage.

 

[Hero999]

There is nothing wrong with the circuit as connected.

The thump will occur whether you like it or not as I assume there is a large capacitor connected to the rectifier on the transformer's secondary which will cause a huge current surge when it charges up. This huge current surge will cause the transformer's windings to vibrate and emit a thump sound.

 

[hotwaterwizard]

So why not put a bleeder resistor across the Capacitor like they do on Electric Motors?

 

[Nigel Goodwin]

So why not put a bleeder resistor across the Capacitor like they do on Electric Motors?

How would that help?, it's to discharge the capacitor!.

 

[sivankls]

Nigel Goodwin Wrote:

No, the CD4060 is there to give a MUCH longer time than a 555 can manage.

Longer time?...but in this case its only few seconds....2 to 4 seconds at the most

 

[sivankls]

Hero99:
The thumb occurs even when the transformer secondary is left unconnected !!