/* * This program source code file is part of KICAD, a free EDA CAD application. * * Copyright (C) 2011 jean-pierre.charras * Copyright (C) 1992-2011 Kicad Developers, see change_log.txt for contributors. * * 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; either version 2 * of the License, or (at your option) any later version. * * 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, you may find one here: * http://www.gnu.org/licenses/old-licenses/gpl-2.0.html * or you may search the http://www.gnu.org website for the version 2 license, * or you may write to the Free Software Foundation, Inc., * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA */ /* see * http://www.desmith.net/NMdS/Electronics/TraceWidth.html * http://www.ultracad.com/articles/pcbtemp.pdf * for more info */ #include #include #include #include #include #include #include extern double DoubleFromString( const wxString& TextValue ); // Key words to read/write some parameters in config: #define KEYWORD_TW_CURRENT wxT( "TW_Track_Current" ) #define KEYWORD_TW_DELTA_TC wxT( "TW_Delta_TC" ) #define KEYWORD_TW_TRACK_COPPER_THICKNESS wxT( "TW_Track_CopperThickness" ) #define KEYWORD_TW_TRACK_LEN wxT( "TW_Track_Len" ) #define KEYWORD_TW_TRACK_COPPER_THICKNESS_UNIT wxT( "TW_Track_CopperThickness_Unit" ) #define KEYWORD_TW_TRACK_LEN_UNIT wxT( "TW_Track_Len_Unit" ) #define KEYWORD_TW_EXTTRACK_WIDTH_UNIT wxT( "TW_ExtTrack_Width_Unit" ) #define KEYWORD_TW_INTTRACK_WIDTH_UNIT wxT( "TW_IntTrack_Width_Unit" ) void PCB_CALCULATOR_FRAME::TW_WriteConfig() { // Save current parameters values in config: m_Config->Write( KEYWORD_TW_EXTTRACK_WIDTH_UNIT, m_TW_ExtTrackWidth_choiceUnit->GetSelection() ); m_Config->Write( KEYWORD_TW_INTTRACK_WIDTH_UNIT, m_TW_IntTrackWidth_choiceUnit->GetSelection() ); m_Config->Write( KEYWORD_TW_TRACK_COPPER_THICKNESS_UNIT, m_TW_CuThickness_choiceUnit->GetSelection() ); m_Config->Write( KEYWORD_TW_TRACK_LEN_UNIT, m_TW_CuLength_choiceUnit->GetSelection() ); m_Config->Write( KEYWORD_TW_CURRENT, m_TrackCurrentValue->GetValue() ); m_Config->Write( KEYWORD_TW_DELTA_TC, m_TrackDeltaTValue->GetValue() ); m_Config->Write( KEYWORD_TW_TRACK_COPPER_THICKNESS, m_TrackThicknessValue->GetValue() ); m_Config->Write( KEYWORD_TW_TRACK_LEN, m_TrackLengthValue->GetValue() ); } void PCB_CALCULATOR_FRAME::OnTWCalculateButt( wxCommandEvent& event ) { // Prepare parameters: double current = std::abs( DoubleFromString( m_TrackCurrentValue->GetValue() ) ); double thickness = std::abs( DoubleFromString( m_TrackThicknessValue->GetValue() ) ); double deltaT_C = std::abs( DoubleFromString( m_TrackDeltaTValue->GetValue() ) ); double track_len = std::abs( DoubleFromString( m_TrackLengthValue->GetValue() ) ); double extTrackWidth; double intTrackWidth; // Normalize units: thickness *= m_TW_CuThickness_choiceUnit->GetUnitScale(); track_len *= m_TW_CuLength_choiceUnit->GetUnitScale(); extTrackWidth = TWCalculate( current, thickness, deltaT_C, false ); intTrackWidth = TWCalculate( current, thickness, deltaT_C, true ); // Display values: wxString msg; msg.Printf( wxT( "%g" ), extTrackWidth / m_TW_ExtTrackWidth_choiceUnit->GetUnitScale() ); m_ExtTrackWidthValue->SetValue( msg ); msg.Printf( wxT( "%g" ), intTrackWidth / m_TW_IntTrackWidth_choiceUnit->GetUnitScale() ); m_IntTrackWidthValue->SetValue( msg ); // Display areas: double scale = m_TW_ExtTrackWidth_choiceUnit->GetUnitScale(); double ext_area = thickness * extTrackWidth; msg.Printf( wxT( "%g" ), ext_area / (scale * scale) ); m_ExtTrackAreaValue->SetValue( msg ); wxString strunit = m_TW_ExtTrackWidth_choiceUnit->GetUnitName(); msg = strunit + wxT( " x " ) + strunit; m_ExtTrackAreaUnitLabel->SetLabel( msg ); scale = m_TW_IntTrackWidth_choiceUnit->GetUnitScale(); double int_area = thickness * intTrackWidth; msg.Printf( wxT( "%g" ), int_area / (scale * scale) ); m_IntTrackAreaValue->SetValue( msg ); strunit = m_TW_IntTrackWidth_choiceUnit->GetUnitName(); msg = strunit + wxT( " x " ) + strunit; m_IntTrackAreaUnitLabel->SetLabel( msg ); // Display resistance (assuming using copper ): double rho = 1.72e-008; // In Ohms*meter double ext_res = rho / ext_area * track_len; msg.Printf( wxT( "%g" ), ext_res ); m_ExtTrackResistValue->SetValue( msg ); double int_res = rho / int_area * track_len; msg.Printf( wxT( "%g" ), int_res ); m_IntTrackResistValue->SetValue( msg ); // Display drop voltage double ext_drop_volt = ext_res * current; msg.Printf( wxT( "%g" ), ext_drop_volt ); m_ExtTrackVDropValue->SetValue( msg ); double int_drop_volt = int_res * current; msg.Printf( wxT( "%g" ), int_drop_volt ); m_IntTrackVDropValue->SetValue( msg ); // Display power loss double loss = ext_drop_volt * current; msg.Printf( wxT( "%g" ), loss ); m_ExtTrackLossValue->SetValue( msg ); loss = int_drop_volt * current; msg.Printf( wxT( "%g" ), loss ); m_IntTrackLossValue->SetValue( msg ); } /* calculate track width for external or internal layers * * Imax = 0.048 * dT^0.44 * A^0.725 for external layer * Imax = 0.024 * dT^0.44 * A^0.725 for internal layer * with A = area = aThickness * trackWidth ( in mils ) * and dT = temperature rise in degree C * Of course we want to know trackWidth */ double PCB_CALCULATOR_FRAME::TWCalculate( double aCurrent, double aThickness, double aDeltaT_C, bool aUseInternalLayer ) { double scale = 0.048; // We are using normalize units (sizes in meters) if( aUseInternalLayer ) scale *= 0.024 / 0.048; // aThickness is given in normalize units (in meters) and we need mil aThickness /= UNIT_MIL; /* formula is Imax = scale * dT^0.44 * A^0.725 * or * log(Imax) = log(scale) + 0.44*log(dT) * +(0.725*(log(aThickness) + log(trackWidth)) * log(trackWidth) * 0.725 = ln(Imax) - ln(scale) - 0.44*log(dT) - 0.725*log(aThickness) */ double dtmp = log( aCurrent ) - log( scale ) - 0.44 * log( aDeltaT_C ) - 0.725 * log( aThickness ); dtmp /= 0.725; double trackWidth = exp( dtmp ); trackWidth *= UNIT_MIL; // We are using normalize units (sizes in meters) and we have mil return trackWidth; // in meters } void PCB_CALCULATOR_FRAME::TW_Init() { int tmp; wxString msg; // Read parameters values: m_Config->Read( KEYWORD_TW_EXTTRACK_WIDTH_UNIT, &tmp, 0 ); m_TW_ExtTrackWidth_choiceUnit->SetSelection( tmp ); m_Config->Read( KEYWORD_TW_INTTRACK_WIDTH_UNIT, &tmp, 0 ); m_TW_IntTrackWidth_choiceUnit->SetSelection( tmp ); m_Config->Read( KEYWORD_TW_TRACK_COPPER_THICKNESS_UNIT, &tmp, 0 ); m_TW_CuThickness_choiceUnit->SetSelection( tmp ); m_Config->Read( KEYWORD_TW_TRACK_LEN_UNIT, &tmp, 0 ); m_TW_CuLength_choiceUnit->SetSelection( tmp ); m_Config->Read( KEYWORD_TW_CURRENT, &msg, wxT( "1.0" ) ); m_TrackCurrentValue->SetValue( msg ); m_Config->Read( KEYWORD_TW_DELTA_TC, &msg, wxT( "10.0" ) ); m_TrackDeltaTValue->SetValue( msg ); m_Config->Read( KEYWORD_TW_TRACK_COPPER_THICKNESS, &msg, wxT( "0.035" ) ); m_TrackThicknessValue->SetValue( msg ); m_Config->Read( KEYWORD_TW_TRACK_LEN, &msg, wxT( "20" ) ); m_TrackLengthValue->SetValue( msg ); // Init formulas text m_htmlWinFormulas->AppendToPage( _( "
The formula (from IPC 2221) is:
" ) ); m_htmlWinFormulas->AppendToPage( _( "
I = K * dT0.44 * (W*H)0.725
" ) ); m_htmlWinFormulas->AppendToPage( _( "
Internal traces : K = 0.024
" ) ); m_htmlWinFormulas->AppendToPage( _( "
External traces: K = 0.048
" ) ); m_htmlWinFormulas->AppendToPage( _( "
where:
" ) ); m_htmlWinFormulas->AppendToPage( _( "
I = maximum current in Amps
" ) ); m_htmlWinFormulas->AppendToPage( _( "
dT = temperature rise above ambient in deg C
" ) ); m_htmlWinFormulas->AppendToPage( _( "
W,H = Width and Thickness in mils
" ) ); }