Sunday, November 13, 2011

Linear Regulator for Sunbeam S7D permanent magnet alternator

The final solution for voltage regulation involves the following components:

  • A 30 amp bridge rectifier
  • NPN power transistor NTE249 with TO-3 case (good for 16 amps)
  • LM317 voltage regulator chip in TO-220 package
  • A big heat sink
  • A multiturn trim pot
  • various resistors
The package neatly fits on the top of the electrical box.  The trick was to mount the heat sink so it was isolated from the frame of the bike.  The trim pot allows minor adjustment to the output voltage so the correct charge rate can be obtained.  Yes, its wasteful, yes it makes heat, but it works!


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