# Help pls

Discussion in 'The Projects Forum' started by haree87, Jan 26, 2009.

1. ### haree87 Thread Starter Member

Jan 19, 2009
16
0
can anyone give me some source for TRIAC with controlled firing angle with AC voltage.

Apr 20, 2004
15,815
283
3. ### haree87 Thread Starter Member

Jan 19, 2009
16
0
hi

the point is i read this already. but i am not able to design a driver circuit using this. i am trying to control a heater coil with a 1-5v with rating of 220v and 5 amps. can someone help me with this????

4. ### haree87 Thread Starter Member

Jan 19, 2009
16
0
hi

the point is i read this already. but i am not able to design a driver circuit using this. i am trying to control a heater coil with a 1-5v with rating of 220v and 5 amps. can someone help me with this???? i've tried few drivers but am not able to get a proper control output to the heater

5. ### beenthere Retired Moderator

Apr 20, 2004
15,815
283
You must think a bit about how triacs are controlled. From the article, you can see that pulsing the gate at a point relative to the phase of the applied voltage waveform is necessary.

The problem for you is to determine how to synchronize the control voltage with the voltage waveform, so a signal of 2.5 volts DC resulted in the triac conducting for 50% of the waveform. That means that you also need a circuit to detect the moment the waveform crosses 0 volts, and use the time between crossings to determine the time that the trigger is applied. Since it's a triac, the trigger will need to be applied on the positive and the negative excursions of the AC voltage waveform.

Doing all this is pretty bulky using discreet components. But little microprocessors like the ATtiny or any small device can do the timing with ease. Then all you need is a zero corssing detector as an input, and use the control voltage input to determine how long after each crossing to trigger the triac.

6. ### haree87 Thread Starter Member

Jan 19, 2009
16
0
hi
i got a driver circuit for my application. but i still have probs.
check the site
http://www.techlib.com/electronics/power_control.htm

let me tell my probs.
1) can someone tell me a different triac tats equalent to the rcat2710 in the circuit becos in my multisim software i do not have this???
2)the resistors r1 and r4 blow off for some reason.
3) the opto coupler does not seem to effectively affect the circuit even wen the dc supply to it is changed.

i've attached the circuit and the output

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7. ### haree87 Thread Starter Member

Jan 19, 2009
16
0
someone pls help