//Electronics utility. Finds parallel resistor pairs to match close tolerance values. // based on the original: // Copyright (C) 2001 Dave Gough // This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; version 2. // This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. // // You should have received a copy of the GNU General Public License along with this program; if not, write to the Free Software Foundation, Inc., // 675 Mass Ave, Cambridge, MA 02139, USA. // COMPLETED IMPROVEMENT // Adding support for more than two paralleled. by JamesNewton@massmind.org 2005/06/09 // POTENTIAL IMPROVEMENTS // Adding support for more resistance series. // Adding support for series connection & possibly more complicated networks // Adding result sort. // Set up arrays of answers var aResult_t=new series(145,0); var aResult_a=new series(145,0); var aResult_b=new series(145,0); var aResult_c=new series(145,0); var aResult_percent=new series(145,100); // Set up list of percentage deviation var isNav, isIe, isOther; if (parseInt(navigator.appVersion)>=4){ if (navigator.appName=="Netscape"){ isNav=true; } else{ isIe=true; } } if (!isNav && !isIe) { isOther=true; } function core_process (fTargetAmp,fTolerance) { // main number crunching routine var aVoltage = 1; //assume 1 volt for easy calculation var fTarget = aVoltage/fTargetAmp; // R = E/I var esqr = 1; //aVoltage ^ 2 //ready for P = E^2 * E var sOut=''; var fUp_limit; var fLow_limit; //upper&lower limits to target resistance var fRes; //target resistance var fDiff_percent=null; var sPolarity_temp=""; var isAnswer=false; //has a match been found? var iAnswer_tally=null; var iBest_diff_index=null; var fBest_diff_value=100; var win2=window.open("","","menubar,scrollbars,status"); sOut = ''; sOut += '\n\n'; sOut+= '\\n'; sOut+='Resistor pairs which parallel to give '+fTarget+' Ohms\n '; sOut+='\n\n'; sOut+= '

Results of resistor set search.

'; sOut+= '

Target Resistance for your current requirement of '+fTargetAmp+' Amps is '+fTarget+' Ohms\n'; // sOut+= '
That resistance, at the full current, will result in a voltage of '+aVoltage+' Volts over all the resistors

\n'; // no point since it is always 1 volt. sOut +='
At the full current, this will dissipate a total of ' + Math.floor( ( fTargetAmp * aVoltage) * 1000 ) / 1000 + ' Watts over all the resistors, but each resistor will dissipate a different amount, shown in (), depending on it\'s value.

\n'; sOut+= '

Tolerance on search = '+fTolerance+'% '; win2.document.write(sOut); sOut = null; fUp_limit=(1.0*fTarget)+(fTarget*(fTolerance/100)); fLow_limit=(1.0*fTarget)-(fTarget*(fTolerance/100)); // Look for solutions with only one resistor. for (var iX = 1; iX <=aResistance_series.length; iX++) { if (aResistance_series[iX]>=fLow_limit & aResistance_series[iX]<=fUp_limit){ isAnswer=true; iAnswer_tally++; //Increment the quantity of answers found aResult_t[iAnswer_tally]=aResistance_series[iX]; aResult_a[iAnswer_tally]=aResistance_series[iX]; //Add first resistor to answer list aResult_b[iAnswer_tally]=0; aResult_c[iAnswer_tally]=0; fDiff_percent=(((aResistance_series[iX]-fTarget)/fTarget)*100); //calculate the percentage difference between target and search result. aResult_percent[iAnswer_tally]=fDiff_percent; if (Math.abs(fDiff_percent)=fLow_limit & fRes<=fUp_limit & aResistance_series[iX]!=fTarget & aResistance_series[iY]!=fTarget){ //Check found pair within spec and not equal to the target resistance! if (aResistance_series[iX] > aResistance_series[iY]){ // Stop loop if repeat pairs found iX=aResistance_series.length;iY=iX; break break } isAnswer=true; iAnswer_tally++; //Increment the quantity of answers found aResult_t[iAnswer_tally]=fRes; aResult_a[iAnswer_tally]=aResistance_series[iX]; //Add first resistor to answer list aResult_b[iAnswer_tally]=aResistance_series[iY]; //Add second resistor to answer list aResult_c[iAnswer_tally]=0; fDiff_percent=(((fRes-fTarget)/fTarget)*100); //calculate the percentage difference between target and search result. aResult_percent[iAnswer_tally]=fDiff_percent; if (Math.abs(fDiff_percent)=fLow_limit & fRes<=fUp_limit & aResistance_series[iX]!=fTarget & aResistance_series[iY]!=fTarget & aResistance_series[iZ]!=fTarget){ //Check found pair within spec and not equal to the target resistance! if (aResistance_series[iX] > aResistance_series[iY] || (aResistance_series[iX] > aResistance_series[iY] && aResistance_series[iY] > aResistance_series[iZ])) { // Stop loop if repeat pairs found iX=aResistance_series.length;iY=iX;iZ=iY; break break break } isAnswer=true; iAnswer_tally++; //Increment the quantity of answers found aResult_t[iAnswer_tally]=fRes; aResult_a[iAnswer_tally]=aResistance_series[iX]; //Add first resistor to answer list aResult_b[iAnswer_tally]=aResistance_series[iY]; //Add second resistor to answer list aResult_c[iAnswer_tally]=aResistance_series[iZ]; //Add second resistor to answer list fDiff_percent=(((fRes-fTarget)/fTarget)*100); //calculate the percentage difference between target and search result. aResult_percent[iAnswer_tally]=fDiff_percent; if (Math.abs(fDiff_percent)200000){ sOut+='

This could be because your target resistance is very high.

'; } if (fTarget<2) { sOut+='

This could be because your target resistance is very low.
You may need to parallel more than three resistors together.
This is more than the Linistepper is designed for.

'; } } else { sOut +='\n (Found '+(iAnswer_tally)+' sets within tolerance)
' +'The closest match is '+aResult_a[iBest_diff_index]+' Ohms @' + (Math.floor((esqr/aResult_a[iBest_diff_index])*1000)/1000) + 'W'; if (aResult_b[iBest_diff_index]>0) sOut +=' paralleled with '+aResult_b[iBest_diff_index]+ ' Ohms @' + (Math.floor((esqr/aResult_b[iBest_diff_index])*1000)/1000) + 'W'; if (aResult_c[iBest_diff_index]>0) sOut +=' paralleled with '+aResult_c[iBest_diff_index]+ ' Ohms @' + (Math.floor((esqr/aResult_c[iBest_diff_index])*1000)/1000) + 'W'; if (aResult_percent[iBest_diff_index]==0){ sOut += ' which is perfect.'; } else { sOut +='\n which is only '+is_positive(decimal(aResult_percent[iBest_diff_index]))+'% out'; } sOut += '

'; sOut +='

Please note: The component selected should aways be rated for double or more of the wattage it is expected to handle. For 1 Watt dissipation, please us 2 or 3 Watt rated resistors.

\n' sOut += '' +''; var bgcolor = "#FFFFFF"; for (var iC = 1; iC <= iAnswer_tally; iC++){ //the minus one is stop the first repeat sOut +='\n'; sOut +='' if (aResult_b[iC]>0) sOut +=''; else sOut +=''; if (aResult_c[iC]>0) sOut +=''; else sOut +=''; sOut +='' +'' +''; if (bgcolor == "#FFFFFF") { bgcolor="#F0F0F0"; } else { bgcolor = "#FFFFFF"; } } sOut +='\n

First (Ohms)	Second (Ohms)	Third (Ohms)	Paralleled result (Ohms)	Deviation (%)
' + aResult_a[iC] + 'Ω @' + (Math.floor((esqr / aResult_a[iC])*1000)/1000) + 'W	' + aResult_b[iC] + 'Ω @' + (Math.floor((esqr/aResult_b[iC])*1000)/1000) + 'W	none	' + aResult_c[iC] + 'Ω @' + (Math.floor((esqr/aResult_c[iC])*1000)/1000) + 'W	none	' +Math.floor(aResult_t[iC]*1000)/1000 +'Ω	' + is_positive(decimal(aResult_percent[iC])) + '

'; } sOut+='

Close this window

'; sOut+='

Release notes

'; sOut+='

Based on the parallel resistance finder from http://www.computertorture.com/noncompliant/parallel/index.html

'; sOut+= '

© Copyright James Newton 2006
This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; version 2.\nThis program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.\nYou should have received a copy of the GNU General Public License along with this program; if not, write to the Free Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.

\n'; sOut+='\n\n\n\n'; win2.document.write(sOut); win2.document.close(); win2.status = 'done'; return true; // Calculation complete } function old_core_process (fTarget,fTolerance){ // main number crunching routine var sOut=''; var fUp_limit; var fLow_limit; //upper&lower limits to target resistance var fRes; //target resistance var fDiff_percent=null; var sPolarity_temp=""; var isAnswer=false; //has a match been found? var iAnswer_tally=null; var iBest_diff_index=null; var fBest_diff_value=100; fUp_limit=(1.0*fTarget)+(fTarget*(fTolerance/100)); fLow_limit=(1.0*fTarget)-(fTarget*(fTolerance/100)); for (var iX = 1; iX <=aResistance_series.length; iX++) { for (var iY = 1; iY <=aResistance_series.length; iY++) { fRes=paracalc_go(aResistance_series[iX],aResistance_series[iY]); if (fRes>=fLow_limit & fRes<=fUp_limit & aResistance_series[iX]!=fTarget & aResistance_series[iY]!=fTarget){ //Check found pair within spec and not equal to the target resistance! isAnswer=true; iAnswer_tally++; //Increment the quantity of answers found aResult_a[iAnswer_tally]=aResistance_series[iX]; //Add first resistor to answer list aResult_b[iAnswer_tally]=aResistance_series[iY]; //Add second resistor to answer list fDiff_percent=(((fRes-fTarget)/fTarget)*100); //calculate the percentage difference between target and search result. aResult_percent[iAnswer_tally]=fDiff_percent; if (Math.abs(fDiff_percent)aResistance_series[iX]){ // Stop loop if repeat pairs found iX=aResistance_series.length;iY=iX; break break } // } } } var fTemp_result=null; sOut = ''; sOut += '\n\n'; sOut+= '\\n'; sOut+='Resistor pairs which parallel to give '+fTarget+' Ohms\n '; sOut+='\n'; sOut+='\n\n'; sOut+= '

Results of resistor pair search.

'; sOut+= '

Target Resistance = '+fTarget+' Ohms

\n'; sOut+= '

Tolerance on search = '+fTolerance+'% '; if (isAnswer!=true) { //Check if any answers found sOut+='

Sorry, could not find a match for your target resistance.

'; if (fTarget>200000){ sOut+='

This could be because your target resistance is very high.

'; } if (fTarget<2) { sOut+='

This could be because your target resistance is very low.
You may need to parallel more resistors together.
Please do not ask me to do it. I cannot be bothered.

'; } } else { sOut +='\n (Found '+(iAnswer_tally-2)+' pairs within tolerance)
' +'The closest match is '+aResult_a[iBest_diff_index] +' Ohms paralleled with '+aResult_b[iBest_diff_index]+ ' Ohms'; if (aResult_percent[iBest_diff_index]==0){ sOut += ' which is perfect.'; } else { sOut +='\n at only '+is_positive(decimal(aResult_percent[iBest_diff_index]))+'% out'; } sOut += '

'; sOut += '' +''; for (var iC = 1; iC < iAnswer_tally-1; iC++){ //the minus one is stop the first repeat fTemp_result=decimal(paracalc_go(aResult_a[iC],aResult_b[iC])); sOut +='\n' +'' +'' +'' +'' +''; } sOut +='\n

First (Ohms)	Second (Ohms)	Paralleled result (Ohms)	Deviation (%)
' + aResult_a[iC] + '	' + aResult_b[iC] + '	' +fTemp_result +'	' + is_positive(decimal(aResult_percent[iC])) + '

'; } sOut+='

Close this window

'; sOut+='

Release notes

'; sOut+='

The latest version of this utility can be found at http://www.computertorture.com/noncompliant/parallel/index.html

'; sOut+= '

© Copyright Dave Gough 2001
This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; version 2.\nThis program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.\nYou should have received a copy of the GNU General Public License along with this program; if not, write to the Free Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.

\n'; sOut+='

'; sOut+='\n\n\n\n'; var win2=window.open("","","menubar,scrollbars"); win2.document.write(sOut); win2.document.close(); return true; // Calculation complete } function is_positive(fQuery){ var sQuery=null; var isPos=true; /* if(isNav){ // Explicit branching used to circumvent the lack of zero's in NN decimal numbers... if (fQuery>=0){ // Adds a plus sign to positive percentage deviation if (fQuery<1){ if (fQuery>0.1){ sQuery='+0'+decimal(fQuery); }else{ sQuery='+'+decimal(fQuery); } }else{ sQuery='+'+decimal(fQuery); } }else{ sQuery=Math.abs(decimal(fQuery)); if (fQuery>-1){ if (fQuery>=-0.1){ sQuery='-0'+decimal(fQuery); }else{ sQuery='-'+decimal(fQuery); } }else{ sQuery='-'+sQuery; } } }else{ if (fQuery>=0){ // Adds a plus sign to positive percentage deviation if (fQuery<1){ sQuery='+'+decimal(fQuery); }else{ sQuery='+'+decimal(fQuery); } }else{ sQuery=Math.abs(decimal(fQuery)); if (fQuery>-1){ sQuery='-'+sQuery; }else{ sQuery='-'+sQuery; } } } */ fQuery=decimal(fQuery); if (fQuery>0){ sQuery='+'+fQuery; }else{ sQuery=fQuery; } return sQuery; } function series(iHow_many, sInitial) { // Sets array values to sInitial this.length = iHow_many; for( var i = 1; i <= iHow_many; i++ ) { this[i] = sInitial; } } function button1_onclick() { // Validate values before processing request var sOut=''; if (document.calc.target_amperage.value<0.001 || document.calc.target_amperage.value>10 ) { alert("Target amperage must be between 0.001 and 10 amps, please change and try again."); return false; } else { if (isNaN(document.calc.target_amperage.value)) { alert('Could not recognise the format of your target amperage. Please try again.'); return false; } if (isNaN(document.calc.tolerance_percent.value)) { alert('Could not recognise the format of search tolerance. Please try again.'); return false; } core_process (document.calc.target_amperage.value,document.calc.tolerance_percent.value); //call main function passing target amperage and tolerance percentage } } function window_onload() { // Initialises resistance series // aResistance_series=new series(145,4.0); aResistance_series=new series(48,4.0); // following fills resistor values aResistance_series[1]=1;aResistance_series[2]=1.1;aResistance_series[3]=1.2;aResistance_series[4]=1.3; aResistance_series[5]=1.5;aResistance_series[6]=1.6;aResistance_series[7]=1.8;aResistance_series[8]=2; aResistance_series[9]=2.2;aResistance_series[10]=2.4;aResistance_series[11]=2.7;aResistance_series[12]=3; aResistance_series[13]=3.3;aResistance_series[14]=3.6;aResistance_series[15]=3.9;aResistance_series[16]=4.3; aResistance_series[17]=4.7;aResistance_series[18]=5.1;aResistance_series[19]=5.6;aResistance_series[20]=6.2; aResistance_series[21]=6.8;aResistance_series[22]=7.5;aResistance_series[23]=8.2;aResistance_series[24]=9.1; for (var i=1;i<=24;i++){ aResistance_series[i+24]=(aResistance_series[i]*10); // aResistance_series[i+48]=(aResistance_series[i]*100); // aResistance_series[i+72]=(aResistance_series[i]*1000); // aResistance_series[i+96]=(aResistance_series[i]*10000); // aResistance_series[i+120]=(aResistance_series[i]*100000); } // aResistance_series[145]=1000000 // aResistance_series[50]=110;aResistance_series[57]=220;aResistance_series[66]=510;aResistance_series[71]=820; // aResistance_series[122]=110000;aResistance_series[129]=220000;aResistance_series[138]=560000;aResistance_series[143]=820000; return true; } function resistname_convert( sResistance ) { //Converts named resistance to float var iDecimal_position=null; //where in string the decimal point is var iMultiplier_position=-2; //where in the string the multiplier is var iMultiplier_value=1; //multiplier value var iDecimal_part=0; //Decimal part of resistance var iMajor_part=0; //Most significant part of resistance iDecimal_position=sResistance.indexOf("."); //find decimal if there is one if (sResistance.indexOf("R")!=-1) {iMultiplier_value=1; iMultiplier_position=sResistance.indexOf("R");} //find multiplier if (sResistance.indexOf("r")!=-1) {iMultiplier_value=1; iMultiplier_position=sResistance.indexOf("r");} if (sResistance.indexOf("K")!=-1) {iMultiplier_value=1000; iMultiplier_position=sResistance.indexOf("K");} if (sResistance.indexOf("k")!=-1) {iMultiplier_value=1000; iMultiplier_position=sResistance.indexOf("k");} if (sResistance.indexOf("M")!=-1) {iMultiplier_value=1000000; iMultiplier_position=sResistance.indexOf("M");} if (sResistance.indexOf("m")!=-1) {iMultiplier_value=1000000; iMultiplier_position=sResistance.indexOf("m");} if (iDecimal_position>-1) {iMultiplier_position=iDecimal_position;} //if decimal prescent put multiplier there numerilogically if (iMultiplier_position < -1.5) { iMultiplier_position=sResistance.length; } if (iDecimal_position=-1) {iDecimal_position=iMultiplier_position;}//if no decimal then make multiplier position iMajor_part=sResistance.substring(0,iDecimal_position); //find bit before decimal point iDecimal_part=sResistance.substring((iDecimal_position+1),sResistance.length); //find bit after decimal sResistance=((iMajor_part+"."+iDecimal_part)*iMultiplier_value); //produce numerical version of resistance return sResistance; } function para3calc_go (fResistance_one,fResistance_two, fResistance_three) { // Calculates parallel resistance of three values return 1/((1.0/fResistance_one)+(1.0/fResistance_two)+(1.0/fResistance_three)); } function paracalc_go (fResistance_one,fResistance_two) { // Calculates parallel resistance of two values var fProduct; var fResult; var fSum; fProduct = fResistance_one*fResistance_two; fSum =((1.0*fResistance_one)+(1.0*fResistance_two)); fResult=fProduct/fSum; return fResult; } function decimal(fFloat) { //converts float value to 2 figure decimal var fStripped=null; fStripped=Math.floor(fFloat*100); fStripped=(fStripped/100); return fStripped; }