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[on:]

Kindly, im writing a code for my voltage divider control circuit .....i have :
1)  analog input pin A0  (signal +1v or -1v or 0v) square wave
2)  two digital outputs  (+ 5v or 0v) for each one ... so i hv 4 states 0 0,0 1,1 0,1 1
Now :
if A0 =   0 v =====>output pins = 0 0
if A0 = +1 v =====>output pins = 1 1
if A0 = -1 v ======>output pins =1 0  or 0 1
------------------------------------------------------

 int analog_in = A0;
 int dig1_out = 9;
 int dig2_out = 10;

void setup () {
serial.begin (9600);
delay (5000);
}

void loop () {
int value=analogRead(analog_in);

if (value = 0) {
  digitalWrite(dig1_out,LOW);
   digitalWrite(dig2_out,LOW);
}
    else   if (value = 1000) {
digitalWrite(dig1_out,HIGH);
digitalWrite(dig2_out,HIGH);
}
else if (value < 0){
digitalWrite(dig1_out,HIGH);
digitalWrite(dig2_out,LOW);
}
delay(20);
}

[Reply #1 on:]

Code:

f (value = 1000) {

Should be ==
Same for the comparison with zero.

If an analogRead returns less than zero, I'd be very worried.

Code:

serial.begin (9600);

The compiler has probably already told you about that one, and your digital pins need to have their pinMode set to OUTPUT.

Please use code tags when posting code.

[Reply #2 on:]

AnalogRead will never return a negative number. If you try and feed -1V into an analog pin you will damage the Arduino.

Secondly, there is always a margin for error with ADC's. The value will not reliably be 1000, for example it may be 997, 999, 1003 - You should allow a range of numbers to be included.

Next, where did 1000 come from? The analogRead value returns a number between 0 and 1023 which represent equal steps between 0v and AREF. If you are using the default reference voltage then 1023=5v, 0=0v, and approximately 204=1v.

[Reply #3 on:]

see now ... but less than zero ... i do not have solution about it

Code:

int analog_in = A0;
 int dig1_out = 9;
 int dig2_out = 10;

void setup () {
serial.begin (9600);
pinMode(dig1_out, OUTPUT);
pinMode(dig2_out, OUTPUT);
delay (5000);
}

void loop () {
int value=analogRead(analog_in);

if (value >= 0) {
    if (value < 5) {     // less than 200 mv
  digitalWrite(dig1_out,LOW);
   digitalWrite(dig2_out,LOW);
} }
    else   if (value <= 209) {
       if (value >= 200) {
digitalWrite(dig1_out,HIGH);
digitalWrite(dig2_out,HIGH);
} }

else if (value < 0){
digitalWrite(dig1_out,HIGH);
digitalWrite(dig2_out,LOW);
}
delay(20);
}

[Reply #4 on:]

but less than zero ... i do not have solution about it

It can't happen, so don't worry about it.

This

Code:

} }

shouldn't happen either.
Always put closing braces on their own line.

[Reply #5 on:]

Would you please at least try to compile your code before re-posting it ?

Code:

sketch_dec29a.ino: In function ‘void setup()’:
sketch_dec29a:6: error: ‘serial’ was not declared in this scope

Also, please hit CTRL-T to correct the code indentation.

[Reply #6 on:]

now ???

Code:

int analog_in = A0;
 int dig1_out = 9;
 int dig2_out = 10;

void setup () {
Serial.begin(9600);
pinMode(dig1_out, OUTPUT);
pinMode(dig2_out, OUTPUT);
delay (5000);
}

void loop () {
int value=analogRead(analog_in);

if (value >= 0) {
    if (value <= 5) {     // less than or equal 200 mv
  digitalWrite(dig1_out,LOW);
   digitalWrite(dig2_out,LOW);
} }
    else   if (value <= 209) {    //about 1 v
       if (value >= 200) {
digitalWrite(dig1_out,HIGH);
digitalWrite(dig2_out,HIGH);
} }

else if (value < 0){              // here is the problem right ?? i need -1 v what i do pls?
digitalWrite(dig1_out,HIGH);
digitalWrite(dig2_out,LOW);
}
delay(20);
}

[Reply #7 on:]

You will find that the way you have built your if-elseif statements won't work quite as you expect:

Code:

if (value >= 0) {
    //value is always greater than zero, so code always reaches here
    if (value <= 5) {
       ...
    }
} else if (value <= 209) {    //about 1 v
    //The first if statement is always true, therefore this bit of code never executes.
    if (value >= 200) {
       ...
    }
}

You are along the right lines though. You just need to consider what you are looking for. For the first if statement you want the value to be >=0 AND <= 5. So based on that you get this:

Code:

if ((value >= 0) && (value <= 5)) {
... //will execute if the value meets both conditions
} else if ((value >= 200) && (value <= 209)) {    //about 1 v
...
}

The problem of negative values however still remains. What you need to do is to take your +/-1v signal and add a bias so that it is within the range of the ADC.

There is one such method which uses just two equally sized resistors. I have attached a schematic.

What the circuit does is att 2.5v onto the signal meaning that when you have -1v, the ADC sees 1.5V, when you have +1v, the ADC sees 3.5v.

How successful this method will be depends on what is driving the +/-1V signal.

[Reply #8 on:]

now ???

A question mark is enough.

I see you didn't press CTRL-T.

Code indentation is key to readability.

You also didn't put each } on its own line, as suggested.

If you ask for help, at least follow the directions. Otherwise why should others bother to help ?

[Reply #9 on:]

 CTL+T .... it is perfect thnx bro

Code:

int analog_in = A0;
int dig1_out = 9;
int dig2_out = 10;

void setup () {
  Serial.begin (9600);
  pinMode(dig1_out, OUTPUT);
  pinMode(dig2_out, OUTPUT);
  delay (5000);
}

void loop () {
  int value=analogRead(analog_in);

  if (value >= 0) {
    if (value <= 5) {     // less than 200 mv
      digitalWrite(dig1_out,LOW);
      digitalWrite(dig2_out,LOW);
    }
  }
  else   if (value <= 209) {
    if (value >= 200) {
      digitalWrite(dig1_out,HIGH);
      digitalWrite(dig2_out,HIGH);
    }
  }

  else if (value < 0){
    digitalWrite(dig1_out,HIGH);
    digitalWrite(dig2_out,LOW);
  }
  delay(20);
}

[Reply #10 on:]

The problem of negative values however still remains. What you need to do is to take your +/-1v signal and add a bias so that it is within the range of the ADC.

There is one such method which uses just two equally sized resistors. I have attached a schematic.

What the circuit does is att 2.5v onto the signal meaning that when you have -1v, the ADC sees 1.5V, when you have +1v, the ADC sees 3.5v.

How successful this method will be depends on what is driving the +/-1V signal.

good idea ....i will try to make the input range 1.5v  ,  2.5v , 4v instead of -1 , 0 , 1

[Reply #11 on:]

Good

Just one more suggestion:

this

Code:

if (value >= 0) {
    if (value <= 5) {     // less than 200 mv

IMHO is clearer if written as:

Code:

if ( (value >= 0) && (value <= 5)) {

[Reply #12 on:]

voltage shifted to (2 v,3v,4v) where 3v is the reference ... see the code and tell me

Code:

int analog_in = A0;
int dig1_out = 9;
int dig2_out = 10;

void setup () {
  Serial.begin (9600);
  pinMode(dig1_out, OUTPUT);
  pinMode(dig2_out, OUTPUT);
  delay (5000);
}

void loop () {
  int value=analogRead(analog_in);

  if  ((value >= 428 ) && (value <= 618))   // refrence range (2.8v - 3.2v)
  {

    digitalWrite(dig1_out,LOW);
    digitalWrite(dig2_out,LOW);
  }

  else   if ((value >= 812) && (value <= 818)) {   //up range (3.8v - 4 v)


    digitalWrite(dig1_out,HIGH);
    digitalWrite(dig2_out,HIGH);
  }



  else  if ((value >= 404) && (value <= 410)) {  //down range (2v - 2.2v)
    digitalWrite(dig1_out,HIGH);
    digitalWrite(dig2_out,LOW);
  }
  else {                                    // for none of the above states

    digitalWrite(dig1_out,LOW);
    digitalWrite(dig2_out,LOW);
  }

  delay(20);
}

[Reply #13 on:]

You may want to check the values you are using for analog in.

If you assume a reference of 5V, and 1024 possible analog values, then you get:

value= 1024 * voltage / 5

If you allow around a +/-200mV from those points you get the following value ranges for your if statements:

Code:

2V = 408 ----->   368 to 451
3V = 614 ----->   573 to 656
4V = 819 ----->   778 to 860

[Reply #14 on:]

Perhaps you could use a multimeter and a simple analog-to-serial sketch, so you can directly check voltage and analog reads.

There should be an example in the ide, anyway it's as simple as:

Code:

void setup() {
    Serial.begin(9600);    // or whatever speed you prefer
}

void loop() {
    int value;

    value = analogRead(0);     // use the correct number for your hardware
    Serial.println(value);
    delay(1000);
}

Upload and open the serial monitor, then keep watching the multimeter readings and the serial values on the screen.

Hope this helps...