firing angle control for an SCR

Projects General Guidance
1

Dear friends

I have an arduino mega board and I used an op-amp as a zero crossing detector, the signal generated by the op-amp is then injected into a digital pin to read it, but unfortunately the signal has dropped to a small value.

What I want is to read the signal from the op-amp then after some time"using delay command " I get a pulse.

By the way, I used a pull down and Pull up resistors.

What's wrong?

can anybody explain what happened?

2

Please post your schematic.
A picture of a hand-drawn circuit diagram is fine.

Pieter

3

Hi,
Welcome to the forum.

Please read the first post in any forum entitled how to use this forum.
http://forum.arduino.cc/index.php/topic,148850.0.html

Can you please post a copy of your circuit, in CAD or a picture of a hand drawn circuit in jpg, png?

Thanks.. Tom... :slight_smile:

4

I'm sorry because I've just subscribed .

5

int pi=30;
int po=26;

void setup() {

Serial.begin(9600);
pinMode(pi,INPUT);
pinMode(po,OUTPUT);
}

void loop() {
int m=digitalRead(pi);
if(m==HIGH)
{

delay(5);
digitalWrite(po,HIGH);
Serial.println("5V");
delay(2);
digitalWrite(po,LOW);
}
else
{
digitalWrite(po,LOW);
Serial.println("0V");
delay(500);
}}

6

It seems you didn't read the link in #2 (or you would have known how to post code properly - i.e. use code tags around it - and please format it properly, do CTRL-T in the IDE), and you also didn't post the circuit diagram as requested, without which it's pretty hard to see what's going on.

7

We also need to see you schematic.

but unfortunately the signal has dropped to a small value.

How do you know that? i.e. Do you have an oscilloscope? ...That 5mS pulse could measure very-low on a multimeter, especially if it's followed by a 500mS delay.

Are you seeing any indication of any switching on the serial monitor? (BTW - The serial.print statements take-up time and could possibly mess-up your timing.)

Your code should be enclosed in code tags which you can get by clicking the menu icon that looks like this: </>

Then your code will look like this:

int pi=30;
int po=26;

void setup() {

  Serial.begin(9600);
pinMode(pi,INPUT);
pinMode(po,OUTPUT);  .....

Re: firing angle control for an SCR

Angle relative to what? ...That 500mS delay is awfully long relative to 50/60Hz line frequency. And, if we're talking about power line voltage it needs to be electrically isolated (optically with a transformer) from the Arduino on both the phase-sensing input and the SCR-controlled output. And, an SCR only conducts in one direction so it only works on half of the AC waveform. (Light dimmers & motor speed controllers usually use TRIACs.)