TRIAC AC switch , need some info

Hi, i am using TRIAC(Bt138-800) as 220AC switch. To arduino board are connected shift registers(74HC595), and and they are sending signals to turn on switch. Using moc3061. R5 is 1W 39R resiztor, instead of R7 would be capacitor 0.01uF 630W ( coulnd find needed size capacitor on proteus to make pcb, so putted resistor, cos they are the same size). R6 and R8 are 1W 330R resisotors. Scheme works fine.
My questions are:

  1. Resistors R6 and R8, their value, what that value gives, can i put lover or higher R resistors, and would be a problem if i put one resistor 1W second 2W?
  2. there would be about 10 switches, current would be from 0.5A and on some swithces might be about 2A. They would be turned up to 12 hours. Do i need some radiators for TRIAC, or they would be fine?

AC switch.BMP (489 KB)

R5 & R7 seem to be very low. They will draw 7.5A and dissipate 1.8 Kw. To top that they do not do anything.

Please crop and resample. Makes it easier for people trying to help you.

Better than that, replace the diagram with one with the actual components and values you are talking about. Its counter-productive to provide the wrong diagram, everyone will get confused.

Agreed. You can always just sketch it on a sheet of paper and take a picture of it, but please, crop the white space and resample to something about 600 to 800 pixels wide.

R6 and R7 or more precise C7, standard values are 100 ohm and 100 nF. Google for[ PMR 209 MC ] RC unit from RIFA / Kemet

R6 and R8 can be higher resistans, together 1 k? or so, not lower than 2x330

Also an resistor Gate to T1 would be fine to avoid false triggering

See figure 10 in the MOC3061M datasheet (http://www.fairchildsemi.com/ds/MO/MOC3061M.pdf) for a typical 220V AC circuit.

Grumpy_Mike: R5 & R7 seem to be very low. They will draw 7.5A and dissipate 1.8 Kw. To top that they do not do anything.

on forum i read that they are needed (R and C at the end) if load is inductive

Pelleplutt: R6 and R7 or more precise C7, standard values are 100 ohm and 100 nF. Google for[ PMR 209 MC ] RC unit from RIFA / Kemet

R6 and R8 can be higher resistans, together 1 k? or so, not lower than 2x330

Also an resistor Gate to T1 would be fine to avoid false triggering

Okej, i am putting resistor from gate to T1.

one more question, if the is no signal, triac is not treigered, how much this switch will consume energy. and what about cooling for triac?

loretka112:

Grumpy_Mike: R5 & R7 seem to be very low. They will draw 7.5A and dissipate 1.8 Kw. To top that they do not do anything.

on forum i read that they are needed (R and C at the end) if load is inductive

That's a snubber network, but you drew two resistors, which is completely different circuit. Yes snubber networks are needed for AC inductive switching (be it a triac or a relay or even just a mechanical switch).

Note that you have R8 drawn incorrectly - it should go between the gate and T1 of the Triac.

Refer to the datasheet. R6 probably should be more like 470 ohms.

The duplication of the series resistor from the MOC to the Triac is a common oddity in “example” or “instructable” circuits. It seems to be largely of decorative value.

The only real reason for the duplication would be where the resistors used are not adequately rated individually for the operating voltage, so putting two in series (which might just as well be on the same connection of the MOC device) effectively doubles their voltage rating.

That is drawn a bit strangely. The point between the Load and 220Vac should be the Neutral line, and the line coming out the bottom of 220Vac should be the Hot line.