Module: Resistor::ColorCode

Defined in:
lib/resistor/color_code.rb

Constant Summary collapse

DIGIT =
4-Band-Code

The 1st and 2nd digit of a resistance value

5-Band-Code

The 1st, 2nd and 3rd digit of a resistance value

{
  :black  => 0,
  :brown  => 1,
  :red    => 2,
  :orange => 3,
  :yellow => 4,
  :green  => 5,
  :blue   => 6,
  :purple => 7,
  :gray   => 8,
  :white  => 9
}.freeze
MULTIPLIER =
4-Band-Code

The 3rd color band indicates the multiplier.

5-Band-Code

The 4th color band indicates the multiplier.

{
  :black  => 0,
  :brown  => 1,
  :red    => 2,
  :orange => 3,
  :yellow => 4,
  :green  => 5,
  :blue   => 6,
  :gold   => -1,
  :silver => -2
}.freeze
TOLERANCE =
4-Band-Code

The 4th color band indicates the tolerance.

5-Band-Code

The 5th color band indicates the tolerance.

{
  :brown  => 1.0,
  :red    => 2.0,
  :orange => 0.05,
  :green  => 0.5,
  :blue   => 0.25,
  :purple => 0.1,
  :gold   => 5.0,
  :silver => 10.0
}.freeze
E12_SERIES = 
{
  1 => [0, 2, 5, 8],
  2 => [2, 7],
  3 => [3, 9],
  4 => [7],
  5 => [6],
  6 => [8],
  8 => [2],
}.freeze
E24_SERIES = 
{
  1 => [0, 1, 2, 3, 5, 6, 8],
  2 => [0, 2, 4, 7],
  3 => [0, 3, 6, 9],
  4 => [3, 7],
  5 => [1, 6],
  6 => [2, 8],
  7 => [5],
  8 => [2],
  9 => [1]
}.freeze
E48_SERIES = 
[
  100, 105, 110, 115, 121, 127, 133, 140, 147, 154, 162, 169, 178, 187, 196, 205,
  215, 226, 237, 249, 261, 274, 287, 301, 316, 332, 348, 365, 383, 402, 422, 442,
  464, 487, 511, 536, 562, 590, 619, 649, 681, 715, 750, 787, 825, 866, 909, 953
].freeze
E96_SERIES = 
[
  100, 102, 105, 107, 110, 113, 115, 118, 121, 124, 127, 130, 133, 137, 140, 143,
  147, 150, 154, 158, 162, 165, 169, 174, 178, 182, 187, 191, 196, 200, 205, 210,
  215, 221, 226, 232, 237, 243, 249, 255, 261, 267, 274, 280, 287, 294, 301, 309,
  316, 324, 332, 340, 348, 357, 365, 374, 383, 392, 402, 412, 422, 432, 442, 453,
  464, 475, 487, 499, 511, 523, 536, 549, 562, 576, 590, 604, 619, 634, 649, 665,
  681, 698, 715, 732, 750, 768, 787, 806, 825, 845, 866, 887, 909, 931, 953, 976
].freeze

Class Method Summary collapse

Class Method Details

.decode(code, options = {}) ⇒ Float

Converts a color code to a resistance value.

Parameters:

  • code (Array<Symbol>, Array<String>) —

    color code

  • options (Hash) (defaults to: {}) —

    a customizable set of options

Options Hash (options):

  • :band_number(4) (Integer)

Returns:

  • (Float) —

    resistance value

Raises:

  • (ArgumentError) —

    Error raised when the supplied color code is not an array, or when the color of the first band is black.



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# File 'lib/resistor/color_code.rb', line 172

def decode(code, options = {})
  raise ArgumentError unless code.is_a? Array
  code = code.map(&:to_sym)
  return 0.0 if code == [:black]
  raise ArgumentError if code[0] == :black

  default = Resistor::Options.new
  options[:band_number] ||= default.band_number

  case options[:band_number]
  when 4 then four_band_decode(code)
  when 5 then five_band_decode(code)
  else raise ArgumentError
  end
end

.encode(ohm, options = {}) ⇒ Array<Symbol>

Converts a resistance value to a color code. The value must be between 0.1 and 99_000_000.

Parameters:

  • ohm (Integer, Float) —

    resistance value

  • options (Hash) (defaults to: {}) —

    a customizable set of options

Options Hash (options):

  • :tolerance(5.0) (Integer, Float)
  • :band_number(4) (Integer)

Returns:

  • (Array<Symbol>) —

    color code

Raises:

  • (ArgumentError) —

    Error raised when the supplied resistance value is less than 0.1.



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# File 'lib/resistor/color_code.rb', line 94

def encode(ohm, options = {})
  return [DIGIT.key(0)] if ohm == 0
  raise ArgumentError if ohm < 0.1

  default = Resistor::Options.new
  options[:tolerance] ||= default.tolerance
  options[:band_number] ||= default.band_number

  case options[:band_number]
  when 4 then four_band_encode(ohm, options)
  when 5 then five_band_encode(ohm, options)
  else raise ArgumentError
  end
end

.five_band_decode(code) ⇒ Object

This method is used by the ‘Colorcode.decode` method when `options` is 5.



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# File 'lib/resistor/color_code.rb', line 198

def five_band_decode(code)
  (DIGIT[code[0]]*100 + DIGIT[code[1]]*10 + DIGIT[code[2]]) *
  10**MULTIPLIER[code[3]]
  .to_f
end

.five_band_encode(ohm, options = {}) ⇒ Object

This method is used by the ‘Colorcode.encode` method when `options` is 5.



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# File 'lib/resistor/color_code.rb', line 137

def five_band_encode(ohm, options = {})
  if ohm < 10
    ohm_str = (ohm*100).to_s.split('')
    [DIGIT.key(ohm_str[0].to_i),
     DIGIT.key(ohm_str[1].to_i),
     DIGIT.key(ohm_str[2].to_i),
     MULTIPLIER.key(-2),
     TOLERANCE.key(options[:tolerance])]

  elsif ohm < 100
    ohm_str = (ohm*10).to_s.split('')
    [DIGIT.key(ohm_str[0].to_i), 
     DIGIT.key(ohm_str[1].to_i),
     DIGIT.key(ohm_str[2].to_i),
     MULTIPLIER.key(-1),
     TOLERANCE.key(options[:tolerance])]

  else
    ohm_str = ohm.to_i.to_s.split('')
    [DIGIT.key(ohm_str[0].to_i), 
     DIGIT.key(ohm_str[1].to_i),
     DIGIT.key(ohm_str[2].to_i),
     MULTIPLIER.key(ohm_str.size - 3),
     TOLERANCE.key(options[:tolerance])]
  end
end

.four_band_decode(code) ⇒ Object

This method is used by the ‘Colorcode.decode` method when `options` is 4.



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# File 'lib/resistor/color_code.rb', line 190

def four_band_decode(code)
  (DIGIT[code[0]]*10 + DIGIT[code[1]]) *
  10**MULTIPLIER[code[2]]
  .to_f
end

.four_band_encode(ohm, options = {}) ⇒ Object

This method is used by the ‘Colorcode.encode` method when `options` is 4.



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# File 'lib/resistor/color_code.rb', line 111

def four_band_encode(ohm, options = {})
  if ohm < 1
    ohm_str = (ohm*100).to_s.split('')
    [DIGIT.key(ohm_str[0].to_i),
     DIGIT.key(ohm_str[1].to_i),
     MULTIPLIER.key(-2),
     TOLERANCE.key(options[:tolerance])]

  elsif ohm < 10
    ohm_str = (ohm*10).to_s.split('')
    [DIGIT.key(ohm_str[0].to_i),
     DIGIT.key(ohm_str[1].to_i),
     MULTIPLIER.key(-1),
     TOLERANCE.key(options[:tolerance])]

  else
    ohm_str = ohm.to_i.to_s.split('')
    [DIGIT.key(ohm_str[0].to_i),
     DIGIT.key(ohm_str[1].to_i),
     MULTIPLIER.key(ohm_str.size - 2),
     TOLERANCE.key(options[:tolerance])]
  end
end