Totally Lost

Projects Programming
1

I'm trying to help my 10 year old son with a project and I know nothing about C++.

We want to cycle a motor if the temp >= 80 degrees and reverse the motor if the temp <= 80 degrees. I tried to create a variable that toggled based on whether the motor had run or not. I keep getting the following error:

"exit status 1
lvalue required as left operand of assignment"

What does that mean? When I search for that error in other topics, I don't even understand the issues they're dealing with. I've tried reading through Language Reference page but I still can't piece it together.

Here's the portion of the code that keeps getting errors:

{
if (temp >= 80 && RunVariable = 0); //temperature equal or above 80F

small_stepper.setSpeed(500); //Max seems to be 500
Steps2Take = 2048; // Rotate CW
small_stepper.step(Steps2Take);
delay(2000);
RunVariable = 1;
break;
}

{
if (temp <= 80 && RunVariable = 1); //temperature equal or above 80F

(small_stepper.setSpeed(500)); //Max seems to be 500
Steps2Take = -2048; // Rotate CCW
small_stepper.step(Steps2Take);
delay(2000);
RunVariable = 0;
break;
}

If you have an answer, please explain like I'm a complete newbie (which I am). Thank you!

2

if (temp >= 80 && RunVariable = 0); <---<<< NO ;

if (temp >= 80 && RunVariable = 0); <---<<< NO ;

Read this:

Always show us the complete sketch, use the code tags icon in the posting menu </>

if (condition)
{
//statement(s)
}

Why are you using break; ?

3

Ah! Thank you!

4

larryd:
if (temp >= 80 && RunVariable = 0); <---<<< NO ;

if (temp >= 80 && RunVariable = 0); <---<<< NO ;

BOTH of those if statements are not testing IF RunVariable is equal to 0. They are BOTH SETTING RunVariable to 0.

'=' is the arithmetic assignment operator
'==' is the arithmetic equality operator

Regards,
Ray L.

5

Was hoping the OP would have discovered = vs == from the url given.

6

RayLivingston:
They are BOTH SETTING RunVariable to 0.

and return 'true' as a test value (assignments always do) mind you, this code does compile though doesn't it ?

7

taichichick:
We want to cycle a motor if the temp >= 80 degrees and reverse the motor if the temp <= 80 degrees.

So, if the temperature is exactly 80 degrees, then what happens?

8

Deva_Rishi:
and return 'true' as a test value (assignments always do) mind you, this code does compile though doesn't it ?

In the case of if (RunVariable = 0), no, the assignment returns 0, or a "false" test value. An assignment always "returns" the value that's assigned to the variable.

9

You can get explanations and examples (not Arduino oriented but still useful) of the instructions and language usage at http://www.cplusplus.com/reference/