for loop help (turn on at a point and turn off when it drops to another point)

I need to make a for loop for a pump to turn on when a tank is 85% full, and then turn off when it gets down to 20%, but I can't figure out how to write this. Any help would be greatly appreciated.

so far I had this, with v being volume, a1 being 85% full, and a2 being 20% full. with how it is now, it will only be on if it is above 85%

if v>=(a1);
        a = 1;
   elseif v<=(a2);
        a = 0;
    else a = 0; 
  end

Answer 1

[Voss]

If I understand the situation, your code needs to have three outcomes: (1) turn the pump on, (2) turn the pump off, (3) leave the pump alone. When the tank is between 20% and 85% full, the pump may be on or off, but it should be left on if it's already on or left off if it's off.

So you'll need more than a=0 and a=1; perhaps another state a=2 that says to leave the pump alone. Or maybe more clear:

if v >= a1
    action = 'turn pump on';
elseif v <= a2
    action = 'turn pump off';
else
    action = 'do nothing';
end

Then if there's code that interacts with the pump, it may need to know whether the pump is already on:

is_pump_on = false;

if is_pump_on && strcmp(action,'turn pump off')
    % take the action of turning the pump off
elseif ~is_pump_on && strcmp(action,'turn pump on')
    % take the action of turning the pump on
end