Class: OhmsLawCalculator

Inherits:
Object
  • Object
show all
Includes:
ActiveModel::Attributes, ActiveModel::Model
Defined in:
lib/ohms_law_calculator.rb

Overview

Solves Ohm's Law (V = I × R) and the power equation (P = V × I) for
whichever of voltage / current / resistance / power is missing, given
any two of the four. Used by the heating-element configuration and
circuit-sizing tools.

Class Method Summary collapse

Instance Method Summary collapse

Class Method Details

.calc(attributes) ⇒ Object

Voltage (V) = Current (I) * Resistance (R)
Power (P) = Voltage (V) * Current (I)



18
19
20
 
# File 'lib/ohms_law_calculator.rb', line 18

def self.calc(attributes)
  new(attributes).calc
end

.difference_in_percent(number1, number2) ⇒ Object 



43
44
45
46
47
48
 
# File 'lib/ohms_law_calculator.rb', line 43

def self.difference_in_percent(number1, number2)
  return 100.0 if number1.nil? || number2.nil?

  d = (BigDecimal((number1 - number2).abs) / number1) * 100
  d.round(1)
end

.validate(attributes, tolerance: 5.0) ⇒ Object 



22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
 
# File 'lib/ohms_law_calculator.rb', line 22

def self.validate(attributes, tolerance: 5.0)
  attributes.dup
  orig_resistance = attributes[:resistance]
  orig_voltage = attributes[:voltage]
  orig_current = attributes[:current]
  orig_power = attributes[:power]
  calc = new(attributes).calc
  resistance_diff = difference_in_percent(calc.resistance, orig_resistance)
  voltage_diff = difference_in_percent(calc.voltage, orig_voltage)
  current_diff = difference_in_percent(calc.current, orig_current)
  power_diff = difference_in_percent(calc.power, orig_power)

  # compare
  errors = []
  errors << "Resistance (Ohm) invalid. #{orig_resistance || 'nil'} different than calculated  #{calc.resistance} by #{resistance_diff} %" if resistance_diff > tolerance
  errors << "Voltage invalid. #{orig_voltage || 'nil'} different than calculated #{calc.voltage} by #{voltage_diff} %" if voltage_diff > tolerance
  errors << "Current (Amps) invalid. #{orig_current || 'nil'} different than calculated #{calc.current} by #{current_diff} %" if current_diff > tolerance
  errors << "Power (Watts) invalid. #{orig_power || 'nil'} different than calculated #{calc.power} by #{power_diff}" if power_diff > tolerance
  errors
end

Instance Method Details

#calc ⇒ Object 



50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
 
# File 'lib/ohms_law_calculator.rb', line 50

def calc
  Rails.logger.debug { "Ohms Law Calculator Inputs: #{attributes.inspect}" }
  if voltage && current
    self.resistance = BigDecimal(voltage) / current
    self.power = (voltage * current).round
  elsif voltage && resistance
    self.current = BigDecimal(voltage) / resistance
    self.power = (BigDecimal(voltage**2) / resistance).round
  elsif voltage && power
    self.current = BigDecimal(power) / voltage
    self.resistance = BigDecimal(voltage**2) / power
  elsif current && resistance
    self.voltage = current * resistance
    self.power = ((current**2) * resistance).round
  elsif current && power
    self.voltage = BigDecimal(power) / current
    self.resistance = BigDecimal(power) / (current**2)
  elsif resistance && power
    self.voltage = Math.sqrt(power * resistance)
    self.current = Math.sqrt(BigDecimal(watts) / ohms)
  elsif voltage
    self.current = nil
    self.power = nil
    self.resistance = nil
  elsif current
    self.voltage = nil
    self.power = nil
    self.resistance = nil
  elsif resistance
    self.voltage = nil
    self.current = nil
    self.power = nil
  elsif power
    self.voltage = nil
    self.current = nil
    self.resistance = nil
  end
  self.power = power&.round
  self.voltage = voltage&.round
  self.current = current&.round(4)
  self.resistance = resistance&.round(5)
  OpenStruct.new(attributes.symbolize_keys).freeze
end