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Controlling a triac BTA12 using 89c2051

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microlab

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hai all
i would like to controll a triac BTA12 using the 89c2051
which will switch on the triac when an interrupt is occured
i want this triac to be on for both the cycles as i am connecting
the triac to switch on a bulb
could anyone please provide the schematic for that?
should i use optocouplers for isolation?
or any other method is there?

thanking you

ml
 

triac switch with led

Hello

Use an Moc 3020 and an bc 547 an few componets and you have the problem solved.

Use similar circuit and just changing the resistor of 470 ohm tow lower if you use 5 V supply.
You can remove the led that indicates the output is on and change the value of the resistor.




Regards
 

Re: triac switch

dear ave
thank you for the reply
when i am using AC for the bulb,i heard that
the triac will be off on the -ve half cycle
is it so?
if so there will be the problem of power loss
and i want to switch on the bulb continously
not to controll the intensity


pls help

ml
 

Re: triac switch

Hello

Int this configuration the triac is on in all cicle becouse the tension that is on the gate is the tension on the main supply an not an dc tensio.
The optoacupler is able to let the triac be fired in the positive cicle and negative

The gate is syncronized with the Main and the triac conduct all the wave.
Just need to put a tensio on the gate of thr transistor and its all ok

Regards
 

Re: triac switch

hai all

thank you for your reply
what should be the value of resistors R1/R2/R3 ?
which is connected from the main to the optocoupler?
i think i can connect the 89c2051 pin directly to the opto coupler
without the transistor to the optocoupler as the 89c2051 can source
current up to 10 mA
i think i have to provide a resistor of 220 ohm from +5v to the opto coupler


thanking you


ml
 

Re: triac switch

dear ave
i could not determine the values of the components
pls specify the value of resistors the optocoupler and triac
should i use snubber circuit?

thanking you

ml
 

Re: triac switch

Hello

the resistor is an 1.2k and the triac can be an bt139.

The snuber is no need becouse there gate is syncronized with the main and the noise is minimal.

Regards
 

Re: triac switch

hai
thank you for your reply
BT 139 is not available here
can i use BTA12 insted?
i am using MOC3021 will it be ok?
should i make any modifications to the circuit?
please reply

regards

ml
 

Re: triac switch

The is no problem
You may need to calculate the reistor to the gate depending the courrent the gate need but no problem

Regards
 

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