Hi.... I have one AC dimming circuit which is working fine when i am checking for a components in that i found Diac. If i want to select Diac for same AC dimming circuit what all the parameters i have to check in the datasheet. Please suggest suitable Diac for me(Voltage: 230V AC)

Thank You

 

Most diacs are 30V, with different Wattages.

 

One method is to look at the manufacturer's literature for the SCR or triac you plan to use and see what diac they are using in their circuit examples.

You might obtain a more detailed response if you mention the SCR or triac you plan to use. If you have a limited selection of diacs available it may be helpful if you listed them too so we don't recommend things you can' t get.

 

One method is to look at the manufacturer's literature for the SCR or triac you plan to use and see what diac they are using in their circuit examples.

You might obtain a more detailed response if you mention the SCR or triac you plan to use. If you have a limited selection of diacs available it may be helpful if you listed them too so we don't recommend things you can' t get.

Thanks for your reply..... Triac i am using is BTA416

 

I think you will have pretty good luck with an arrangement like this.



Just substitute the 1K resistor with a pot. The important thing is to use about 1 uf capacitor and an approximately 30 volt diac (Hey, this is analog!) That should give you a plenty good gate pulse for your BTA416.

http://www.es.co.th/detail.asp?Prod=008300485

 

No- the timing cap and resistor depend on the mains voltage. If you want a say 45 degree delay, you have to check the math for R/C as well as make sure the cap can supply enough gate current.
BTA41 is not sensitive-gate. Another dimmer circuit uses extra diodes to getr better control at the low end, by discharging the timing cap every cycle.

 

Yes. The thread starter stated that his mains voltage is 230 VAC.

 

I find your circuit has a large timing cap at 1uF. It would mean the potentiometer has to be high(er) power and you need more than 4.1msec delay I would think? If you could note intended mains voltage/frequency on your schematic so 120VAC use doesn't give sad results. This schematic for a cheapola eBay "4000W dimmer" after I did a few mods. It uses the extra diodes to reset the timing capacitor after each mains cycle, which gives better control.
More can be found in figure AN1003.12 Teccor App note AN1003 pdf which is a very good read.
I ended up doing LTSpice simulations to get the original to work over a decent range and to not roast the potentiometer.