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Alarm circuit for car alternator

  • US 4,254,396 A
  • Filed: 05/14/1979
  • Issued: 03/03/1981
  • Est. Priority Date: 05/23/1978
  • Status: Expired due to Term
First Claim
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1. An alarm circuit for indicating a defect in a diode-rectified alternator for charging a car battery having positive and negative terminals connected for charging, respectively, to first and second alternator output terminals of said alternator at which rectified positive and negative voltages are provided, the voltage between said first and second alternator output terminals being maintained at a normal running output voltage for charging the battery during normal alternator operation, said alarm circuit comprising:

  • an electrical commutation circuit having an output path and a control terminal for providing current flow through said output path in response to when a control voltage at the control terminal exceeds a predetermined threshold voltage with respect to said second alternator output terminal,a warning device connected with and controlled by said output path between said battery terminals, anda voltage divider for providing said control voltage, said divider having a central point connected to said control terminal and two end terminals connected, respectively, to first and second auxiliary terminals of said alternator, said first and second auxiliary terminals providing potentials substantially equal to the potentials at said first and second alternator output terminals, respectively, during the normal running operation of said alternator,wherein said first auxiliary alternator terminal and said first alternator output terminal are directly connected together to be maintained at substantially the same potential, while diode means are coupled between said second auxiliary terminal and said second alternator output terminal to isolate said second auxiliary terminal and said voltage divider from said second alternator output terminal and one of said positive and negative battery terminals, wherein said diode means prevents said battery from supplying current flow through said voltage divider and wherein said control voltage exceeds said threshold voltage fr both low and high voltage outputs between said first and second alternator output terminals thereby causing excitation of said warning device, and said control voltage is less than said threshold voltage for the normal running voltage output, between said low and high voltage outputs, being provided between said first and second alternator output terminals.

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