230V AC switching

[haxan]

Hi.

I want to switch a 230V AC supply for bulbs using a 5 volt signal. I do not want to use relays, just triacs.

The problem is i dont know if the load is always going to be bulbs (resistive) or Energy Savers (inductors). For this reason i want to confirm that will the following circuit work for both?

 

[Hero999]

Energy savers use electronic ballasts these days.

Use an opto-isolator with a zero crossing unit such as the MOC3041 and there won't be any problems. If you're worried you can connect a snubber network across the TRIAC but I don't see any need for it.
https://www.electro-tech-online.com/custompdfs/2010/03/moc3041.pdf

EDIT:
Are you using a microcontroller?

You could use a pulse transformer (you can make this yourself with a ferrite bead) as an alternative to an opto-isolator, along with zero corssing of course.

 

[Dvinchy]

Look out for the circuit you brought. There really is not a great scheme above where a triac whose named like TIC 226 will supposed to carry out a dead short circuit.

 

[Gobbledok]

Look out for the circuit you brought. There really is not a great scheme above where a triac whose named like TIC 226 will supposed to carry out a dead short circuit.

LOL yes when the triac is turned on there will be a loud noise and a bit of smoke and your triac won't be there anymore.


If the connector is treated like the contacts of a SPST switch, rather than L & N, then that won't blow up.

 

[haxan]

Yes Hero999, the basic idea is to attach it with microcontroller. I can use MOC3041, no problem.

Here is a circuit i took out from the datasheet you recommended. What is a snubber circuit?



I have a TRIAC BT137 (600E), i hope it wont give me any problems. What should be the voltage rating of the capacitor and resistor wattages (.25, .5, 1).
Sorry Gobbledok, i didn't understand what you meant, please kindly explain a little bit

 

[Hero999]

It looked like you were going to just connect the TRIAC across the mains in the first schematic but I knew what you meant.

I also notice that both schematics both have a snubber network so even if the load is inductive, it won't be a big problem.

I've dug out my old thread about using a ferrite bead to make a pulse transformer. As you're dealing with real mains, you'll probably need to use properly insulated wire for both the primary and secondary, enamel isn't good enough to provide isolation so you'll probably need to use a slightly larger core than I did.

https://www.electro-tech-online.com...-transformer-using-a-ferrite-bead-core.36019/

 

[haxan]

Thank you hero999 but i do not understand the need of ferrite bead in the circuit.

If i use the exact setting as mentioned in the above post's image (**broken link removed**) wont it work alright?

 

[Hero999]

There's no need for the ferrite circuit, it's just an alternative way of solving the problem, it'll be cheaper but will be slightly harder to make, the choice is yours.

 

[haxan]

Thank you hero999, i will try without the ferrite bead for now, if there is a problem i will try it with the ferrite bead.

Is it possible to control the phase of an AC fan using the same circuit as well ? For example i use MOC3020 and use a controller to check for zero crossing and then firing the triac to control speed of AC Fan?

 

[Hero999]

Why didn't you say you wanted to do phase control before?

The MOC3041 contains a zero crossing unit so is not suited to phase control because it only turns on when the mains voltage is near 0V.

Use the MOC3021 or ferrite bead for phase control.

Zero crossing checking can be done by monitoring the AC voltage before the rectifier.

 

[haxan]

Why didn't you say you wanted to do phase control before?

I want to do both (switching, phase control) in two different projects. Just wanted to confirm if the circuit will remain same in both (other than the MOC IC of course)

 

[Hero999]

Look out for the circuit you brought. There really is not a great scheme above where a triac whose named like TIC 226 will supposed to carry out a dead short circuit.

No.

The TRIAC is supposed to be connected in series with a load such as a lamp and will never switch a dead short.

The original schematic may have appeared that way but it's obvious the plan is to connect it in series with the load.

 

[haxan]

I am going to make the PCB of the circuit above, any advice on the Trace size for (220V, triacs are for 4Amps)

 

[Hero999]

The CircuitCalculator.com Blog Current vs. Trace Thickness and Temperature vs. Copper Density

 

[haxan]

The above circuit (without the snubber) is working fine with simple bulb and energy saver both. Now my main concern is the heat the triac will generate. So far for 40W load, the triac stays at room temp. Should i put a heat sink just to be sure nothing will burn up.

The problem is i am trying to make a set of 8 triacs and put them in a small circuit box and place in the wall switch board. The heat sinks will take too much space, any idea how to reduce the circuit size into something like 3 x 5 x 1 inches (length x width x height).

 

[Hero999]

Look at the TRAIC's datasheet.

Note the voltage drop vs current.

Calculate the power dissipation.

Use the thermal resistances specified to calculate the temperature rise without a heat sink and add one if it exceeds the maximum temperature rating.

 

[haxan]

Another problem with the Energy Saver is that when i turn off the power (pull out the plug) the energy saver blinks and then turns off. Other bulbs turn off simply without glowing (blinking).

Can it be because i have not yet installed the snubber portion of the circuit?

Added: Sorry other bulbs also blink but with very less power so doesn't feel much.

 

[santosh gairhe]

please help me with moc3021

**broken link removed**hello haxan this is me santosh gairhe...
now i'm doing final year project in electrical engineering.
I need to switch on and off loads using thyristor/Triacs so i need opto isolator moc3021 for this purpose. I hab bought moc3o21 from the market and connected the same circuit as shown in the data sheet but i faced one problem. When i switch on moc3021 with vcc 5v and Rin 330 ohm the Triac output drive becomes conducting but now even if i cut off the vcc supply the output is still conducting ( output is latched). I dont know how to switch off the output.
will u please help me with this.....
I'll be very thankful if u help me..

>>gairhe

 

[Hero999]

You can't use image tags with files on your computer, unless you have it set up as a server.

You need to attach the file to the post.

And please use PNG, not JPG for images.

 

[ericgibbs]

**broken link removed**
hi hero,
This latest site ware does provide for IMAGE tags from your PC or a URL.

**broken link removed**