/* This script and many more are available free online at
The JavaScript Source!! http://javascript.internet.com
Created by: Curt Turner :: http://www.turner3d.net
Modified for use at vk3khb.gak.net.au 02-2010 */

ohmStr=String.fromCharCode(937);
base10=Math.log(10);
function preLoad(){
  // preload color-band images
  arrCols=new Array();
  srcBase=document.getElementById('sel1');
  for(i=0;i<srcBase.length;i++){
    arrCols[i]=srcBase.options[i].value;
  }
  arrImg=new Array();
  for(i=0;i<arrCols.length;i++){
    for(j=0;j<3;j++){
      arrImg[i*3+j]=new Image();
      arrImg[i*3+j].src='images/resistor/band_'+arrCols[i]+(j+1).toString()+'.jpg';
    }
  }
  pre1=new Image();
  pre1.src='images/resistor/band_d3.jpg';
  pre2=new Image();
  pre2.src='images/resistor/band_s3.jpg';
  pre3=new Image();
  pre3.src='images/resistor/band_mult_s.jpg';
}
function selCol(what,band){
  // display color-band image
  eval("document.getElementById('band"+band+"').src='images/resistor/band_"+what.value+band+".jpg';");
}
function selTol(){
  // display tolerance band, set tolerance numeric dropdown
  document.getElementById('mult').src='images/resistor/band_mult_'+document.getElementById('tolerance').value+'.jpg';
  document.getElementById('tolNum').selectedIndex=document.getElementById('tolerance').selectedIndex;
  calc();
}
function tolRev(){
  // display tolerance band, set tolerance color dropdown
  document.getElementById('tolerance').selectedIndex=document.getElementById('tolNum').selectedIndex;
  document.getElementById('mult').src='images/resistor/band_mult_'+document.getElementById('tolerance').value+'.jpg';
  calc();
}
function calc(){
  // calculate values from color selections
  pow=document.getElementById('sel3').selectedIndex;
  if(pow==10)pow=-1; //gold
  if(pow==11)pow=-2; //silver
  //note: Multiplied resistance value by 100 (pow+2), rounded to nearest integer, then divided
  //  result by 100 to compensate for Javascript exponentiation errors (only need 2 significant digits)
  res=Math.round((document.getElementById('sel1').selectedIndex*10+document.getElementById('sel2').selectedIndex)*Math.pow(10,pow+2))/100;
  if(res>990000){
    document.getElementById('multSel').selectedIndex=2;
    res/=1000000;
  }else if(res>990){
    document.getElementById('multSel').selectedIndex=1;
    res/=1000;
  }else{
    document.getElementById('multSel').selectedIndex=0;
  }
  if(res>999){
    res=res.toString();
    res=res.substr(0,res.length-3)+','+res.substr(res.length-3,3);
  }
  tolOut=5*Math.pow(2,document.getElementById('tolerance').selectedIndex)
  document.getElementById('txtNum').value=res;
}
function calcRev(){
  // calculates color selections from numeric input
  // convert input to ohms
  document.getElementById('errSpan').innerHTML='';
  base=document.getElementById('txtNum').value;
  if(parseFloat(base).toString()=='NaN')return false;
  if(base==0)return false;
  multBy=Math.pow(1000,document.getElementById('multSel').selectedIndex);
  res=base*multBy;
  if((res>99000000000)||(res<.1)){
    inputError();
    return false;
  }
  raisedTo=Math.floor(Math.log(res)/base10);
  res=Math.round(res/Math.pow(10,raisedTo-1))/10;
  d1=Math.floor(res);
  d2=Math.round((res-d1)*10);
  if(d1==10){
    d1=1;
    d2=0;
    raisedTo+=1;
  }
  mIndex=raisedTo-1;
  if(mIndex==-1)mIndex=10;
  if(mIndex==-2)mIndex=11;
  document.getElementById('sel1').selectedIndex=d1;
  selCol(document.getElementById('sel1'),1);
  document.getElementById('sel2').selectedIndex=d2;
  selCol(document.getElementById('sel2'),2);
  document.getElementById('sel3').selectedIndex=mIndex;
  selCol(document.getElementById('sel3'),3);
}
function inputError(){
  for(i=1;i<4;i++){
    eval("document.getElementById('sel"+i+"').selectedIndex=0;");
    eval("document.getElementById('band"+i+"').src='band_k"+i+".jpg';");
  }
  document.getElementById('errSpan').innerHTML="out of range";
}