Re: SCR gate controller circuit using arduino

Helloo to all... i need an urgent help for my project related to rectifier consist of 4 anti parallel SCR and i need to give a firing pulses to each thyristor. Firing pulses must on the basis of the analog voltage available at analog pin. it means that delay that are required should be according to to analog voltage availble. here i m posting my code for that. in output i only got a half wave in positive cycle. i want a help regarding my code whether it is correct or not. basically this is a controlled rectifier.

int INTpin= 2; int INTpin1= 3; volatile int ADCpin= A0; int SCRpin1= 9; int SCRpin2= 10; volatile int alpha; volatile int d;

void setup (){ pinMode (SCRpin1, OUTPUT); pinMode (SCRpin2, OUTPUT); analogReference (DEFAULT); attachInterrupt (0, positive, RISING); attachInterrupt (1, negative, FALLING); }

void positive(){ { ADC = analogRead(ADCpin); alpha = map(ADC, 1024, 0, 0, 180); d = (ADC*5/1000)*1.955; delay ((alpha*10)/180); digitalWrite(SCRpin1, HIGH); delay (d); digitalWrite(SCRpin1, LOW);

} }

void negative(){ { ADC = analogRead(ADCpin); alpha = map (ADC, 1024, 0, 0, 180); d = (ADC*5/1000)*1.955; delay ((alpha*10)/180); digitalWrite(SCRpin2, HIGH); delay (d); digitalWrite(SCRpin2, LOW);

} } void loop (){ }

i did this by assuming 2.5V at analog pin. thus it makes "ADC = 512, alpha=90, d= 5.00ms, delay=5ms."

but this is only correct for 2.5V. I am not able to do it for any other voltage at analog pin. i have attched my circuit in proteus and waveform. anytime suggestions... need help....

thanks..

. i have attched my circuit in proteus and waveform.

Where?

A schematic you could read would be way way better.

What is “4 anti parallel SCR”?

Weedpharma

What is proteus? waveform?

Please post schematics that we can read without whatever cad software you happen to know.

weedpharma: What is "4 anti parallel SCR"?

Weedpharma

= Connected as a standard rectifier bridge, each diode controlled by a gate.

To do this, you must use an optocoupler for each gate-cathode in the bridge SCR's to isolate the different cathode levels. The optocoupler inputs can be driven off a single Arduino digital output, using a series resistor to each optocoupler.

You will also need a zero crossing detector connected to the AC side, to get a start signal pulse input for the delay time. Then you can decide how much delay you want from each zero crossing, to fire all 4 SCR's at one time. Only the 2 SCR's that are forward biased on the incoming AC, will open for the rest of the cycle.

@ Admin/Mod : I believe this thread should be moved to the General electronics forum.

soorrryyy for last time. due to slow internet connection it were not uploaded. here it is.

and i used both ZCD for detect zero crossing and also using opto coupler i.i. moc3021,. but i am not getting any pulses.

can u give a me correct schematicof opto coupler. beacause i tried almost 4 to 5 optocoupler.

You need series resistors to the inputs of the optotriacs... Set for 20mA and most optocouplers will be happy. Without a resistor the optocoupler will fry (and possibly the Arduino pin too).

The configuration is an inverter/motor-driver/rectifier bridge, not antiparallel! Two antiparallel SCR's would be pointless as a triac is the obvious alternative.

It seems to be synchronous rectifier circuit?

Its confusing to draw schematics backwards - signals should flow left to right (OK, you could call the opto couplers a feedback path, but still).

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shahid1993:
soorrryyy for last time. due to slow internet connection it were not uploaded. here it is.

and i used both ZCD for detect zero crossing and also using opto coupler i.i. moc3021,. but i am not getting any pulses.

can u give a me correct schematicof opto coupler. beacause i tried almost 4 to 5 optocoupler.