# First Ruby program by Steve DeRose, sderose*acm.org.
# Written 3/8/03, last updated 5/13/03.
# I hereby place this program in the public domain.

# Calculates resistor values for Radio Shack Lm371 adjustable voltage regulator,
# and write out the result as an XHTML table.

# Vout = 1.25 * ( 1 + r2/r1 )
# Vout/1.25  = 1 + r2/r1
# (Vout/1.25) - 1 = r2/r1
# ((Vout/1.25) - 1) * r1 = r2

# a is the list of output voltages to be calculated for
a = [ 1.25, 1.5, 2.5, 3, 4.5, 5, 6, 7.2, 7.5, 9, 10, 12, 14, 14.4, 16, 20, 24, 28, 32, 36, 40, 44, 48 ]

# r1 and rr2 are two values for r1, for which the respective r2 values are calculated
r1 = 240
rr1 = 220

puts "<h2>Resistor table for LM317 adjustable voltage regulator</h2>"

# a.each { |v| puts v, v }
# a.each { |v| puts v , (((v/1.25) - 1) * r1) }

# puts "Number of entries ", a.length
puts "<table border='1' align='center'>"
puts "<tr>"
puts "<th>Voltage out</th>"
puts "<th>r2 w/<br />r1 = " << r1.to_s << "ohms</th>"
puts "<th>r2 w/<br />r1 = " << rr1.to_s << "ohms</th>"
puts "</tr>"

for i in 0...a.length
   r2 =  (((a[i]/1.25) - 1) * r1) 
   rr2 = (((a[i]/1.25) - 1) * rr1) 
   s = "<tr><td class='volts'>" << a[i].to_s << "</td> <td class='ohms'>" << r2.to_s 
   s = s << "</td> <td class='ohms2'>" << rr2.to_s << "</td></tr>"
   puts s
end

puts "</table>"