electronics-led-volts-nm

#!/usr/bin/perl
use v5.24; use strict; use warnings;
use bansi; # Used for colors (whi, rst, etc. yel, bmag, bgmag (background))

# Todo:
# * Add additional units if needed to usage() and our support
# * If frequency given in a hz unit convert to needed wavelength first
# * Perform calc() which evaluates number, units, and calculation
#   (Which I believe is (1240/nm)
# * Output result to user

sub usage {
	print <<~"EOT";

		${whi}Shows voltage needed for producing light at a given wavelength$rst
		led-volts-nm [#]                - Plain number taken as nm
		led-volts-nm [#[nm,um,mm,m,km]] - Units provided
		led-volts-nm [#[M,k]hz]         - User provides frequency
		led-volts-nm -e                 - Give explanation
		led-volts-nm -E                 - Give explanation without utf8
		
		Options:
		  -e - Output explanation/derivation
		  -E - Output explanation without utf8
		EOT
}

our $sym_lambda = 'λ';
our $sym_nu = 'ν';
our $sym_e = 'E';
our $sym_h = 'h';
our $sym_c = 'c';

# Subroutine to switch symbols to ASCII
sub syms_to_ascii {
	$sym_lambda = 'lambda';
	$sym_nu = 'nu';
	$sym_e = 'E';
	$sym_h = 'h';
	$sym_c = 'c';
}

sub str_help { # String of full explanation
	my $sect = "$bgblu$whi";  # Section headings
	my $nums = "$yel";        # Numbers
	my $sym = "$bcya";        # Symbols
	my $equ = "$whi";         # Equations
	my $unit = "$bmag";       # Units
	return <<~"END_HELP";

		${sect} The Planck-Einstein Relation ${rst}
		The energy ($equ$sym_e$rst) of a photon is given by the Planck-Einstein relation:
		   $equ$sym_e = $sym_h * $sym_nu$rst
		where $equ$sym_h$rst is Planck's constant (${nums}6.626 x 10^-34 ${unit}Js$rst)
		and $equ$sym_nu$rst is the frequency of the photon.

		The frequency ($sym$sym_nu$rst) can be related to the wavelength ($sym$sym_lambda$rst)
		by the speed of light ($sym$sym_c$rst): $equ$sym_nu = $sym_c / $sym_lambda$rst

		Therefore, the energy of a photon can also be written as: $equ$sym_e = ($sym_h * $sym_c) / $sym_lambda$rst

		${sect} Conversion to Electron Volts ${rst}
		The energy calculated from the Planck-Einstein relation is in joules ($equ${unit}J$rst)
		when using SI units. However, it is often more convenient to express
		photon energy in electron volts (${unit}eV$rst).

		${sect} The Simplified Formula ${rst}
		By substituting $sym$sym_h$rst, $sym$sym_c$rst, and the conversion factor from joules to electron volts
		into the equation, and setting $sym$sym_lambda$rst in nanometers (${unit}nm$rst) for practical use, we
		derive a simplified formula: $equ$sym_e (eV) = 1240 / $sym_lambda (nm)$rst

		${sect} Application to LEDs ${rst}
		For LEDs and other semiconductor devices, the energy calculated by this
		formula represents the photon energy corresponding to the band gap of
		the material, which determines the color (wavelength) of the light emitted.

		END_HELP
}

sub calc {
	my ($us) = @_; # User-provided string (number or number with units)
	my $wavelength_nm; # Wavelength in nanometers

	# Regular expressions for detecting units and converting to nm
	if ($us =~ /^(\d+\.?\d*)\s*(nm)?$/i) {
		$wavelength_nm = $1; # Directly in nm
	} elsif ($us =~ /^(\d+\.?\d*)\s*um$/i) {
		$wavelength_nm = $1 * 1000; # Micrometers to nm
	} elsif ($us =~ /^(\d+\.?\d*)\s*mm$/i) {
		$wavelength_nm = $1 * 1_000_000; # Millimeters to nm
	} elsif ($us =~ /^(\d+\.?\d*)\s*m$/i) {
		$wavelength_nm = $1 * 1_000_000_000; # Meters to nm
	} elsif ($us =~ /^(\d+\.?\d*)\s*km$/i) {
		$wavelength_nm = $1 * 1_000_000_000_000; # Kilometers to nm
	} elsif ($us =~ /^(\d+\.?\d*)\s*(M|k)?hz$/i) {
		my $frequency = $1;
		my $prefix = $2 // '';
		$prefix = lc $prefix;
		$frequency *= 1_000_000 if $prefix eq 'm';
		$frequency *= 1_000 if $prefix eq 'k';

		# Convert frequency to wavelength
		my $speed_of_light_m_s = 299_792_458; # Speed of light in m/s
		my $wavelength_m = $speed_of_light_m_s / $frequency;
		$wavelength_nm = $wavelength_m * 1_000_000_000;
	} else {
		print "Invalid input or unsupported units.\n";
		return;
	}

	# Perform calculation (1240 / wavelength in nm)
	my $voltage = 1240 / $wavelength_nm;
	my $vfmt;

	if ($voltage > -.05 && $voltage < .05)      { $vfmt = "%E eV"; }
	elsif ($voltage > -1 && $voltage < 1)       { $vfmt = "%.5f eV"; }
	elsif ($voltage > -2 && $voltage < 2)       { $vfmt = "%.4f eV"; }
	elsif ($voltage > -5 && $voltage < 5)       { $vfmt = "%.3f eV"; }
	elsif ($voltage > -1000 && $voltage < 1000) { $vfmt = "%.2f eV"; }
	else                                        { $vfmt = "%E eV"; }

	printf "Voltage needed: ".$vfmt."\n", $voltage;
}

if (@ARGV<1 || grep {/^-(h|-help)$/} @ARGV) { usage(); exit; }
if (grep {/^-E$/} @ARGV) { syms_to_ascii(); }
if (grep {/^-e$/i} @ARGV) {
	print str_help();
} else {
	my $s = shift @ARGV;
	calc($s);
}