# Motor with ultrasonic sensor

I am new to programming so bear with me. I am writing a simple code to control a motor such that the motor will turn at full speed as long as the sensor does not detect an object within 5" of the sensor. If it does see something at 5 inches or less, then I want to motor to stop. My question is this: When using an IF statement, do you have to have the ELSE, or can you simply do two IF statements with no ELSE?

Here is my example:

``````int motorpin1 = 10 , motorpin2 = 11;
int trig = 12;
int echo = 9;
float distance;
float time;

void setup()
{
pinMode (motorpin1, OUTPUT);
//yellow wire
pinMode (motorpin2, OUTPUT);
//blue wire

pinMode (trig, OUTPUT);
pinMode (echo, INPUT);
Serial.begin (9600);

}

void loop()
{
// setup ultrasonic sensor to control
//motor
digitalWrite(trig, LOW);
delayMicroseconds(2);
digitalWrite(trig, HIGH);
delayMicroseconds(10);
digitalWrite(trig, LOW);
time = pulseIn(echo, HIGH);
distance = time/148.1;

Serial.println(distance);

if distance <5,digitalWrite (motorpin1, LOW);
digitalWrite (motorpin2, LOW);

if distance >=5, digitalWrite (motorpin1, HIGH);
digitalWrite (motorpin2, LOW);
delay (1000); //wait for 1 second
``````

Is there a better way to do this with an ELSE statement? I want to capture the parameter where the code controls the specific parameters of >5 and then <or=5. Also, my next thing is to pause, and reverse the motor if after 1 second, the sensor still sees an object <=5.

Definitely a learning curve for this old brain of mine!

• did you try to compile your code? Commented Sep 7, 2022 at 14:58
• start thinking about `if` statements in your everyday life ... they happen all the time ... for example `if (red light) {stop car};` ... then think if there would be an `else` block .... don't forget that you can put any command in the `else` block ... `else if` is useful Commented Sep 7, 2022 at 15:02

You can do something along the line of

``````if (distance < 5) {
digitalWrite (motorpin1, LOW);
}
else {
digitalWrite (motorpin1, HIGH);
}
``````

It seems like you only set `motorpin2` to `LOW` and never to `HIGH`. If you don't want to set it `HIGH`, move that line to the `setup()` section. There is no need to keep setting it `LOW`.

• you could use a C++ ternary operator ... replace your six lines with one line ... `digitalWrite (motorpin1, (distance < 5) ? LOW : HIGH );` Commented Sep 7, 2022 at 18:22
• @jsotola Well, if you're to bother going that route, the ternary operator is itself unnecessary: `digitalWrite (motorpin1, !(distance < 5));` or just `digitalWrite (motorpin1, distance >= 5);` Commented Sep 7, 2022 at 20:55
• it depends on if `HIGH` is equal to `true` and `LOW` is equal to `false` Commented Sep 7, 2022 at 21:13
• You could use a ternary operator and I do this myself, but since the question is asked by a beginner, I valued readability over reducing number of lines.
– jkp
Commented Sep 8, 2022 at 7:17
• @jsotola, something considered and discarded. No one in their right mind will design a core with LOW as truthy an vice versa. Anyway, particularly for new people it's okay the way it is. Commented Sep 8, 2022 at 17:18