var maxSets = 1;
var idRows = new Array("a","b","c","d");
var mySet = "set1";
var counter = 1;
var pathToImg = "";
var intervalID;

var randomVar1 = 0;
var randomVar2 = 0;
var randomVar3 = 0;

function changeImg(id,target) {
	 document.getElementById(id).src = target; 
}

function getRandomSet() {
  randomVar1 = Math.random().toString().substring(2,3);
  if (maxSets > 10) {
    randomVar2 = Math.random().toString().substring(2,3);
  }
  if (maxSets > 20) {
    randomVar3 = Math.random().toString().substring(2,3);
  }
	 counter = parseFloat(randomVar1) + parseFloat(randomVar2) + parseFloat(randomVar3);
	 if (counter > maxSets || counter == 0) {
		  getRandomSet();
		}
}

function changeGrid() {
 	getRandomSet();
	 mySet = "set" + counter; 
  for (i = 0;i < idRows.length;i++) {
    for (k = 1; k <= 5; k++) {
      changeImg(idRows[i]+k,pathToImg+"images/grid/"+mySet+"/"+idRows[i]+k+".jpg");
		  }
  }
}

intervalID = setInterval("changeGrid()",5000);