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

• Current Assignee: PEI 1991 Acquisition Incorporated
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Saudax, Pierre
• Primary Examiner(s): Waring, Alvin H.
• Application Number:
  US06/038,965
• Time in Patent Office: 659 Days
• Field of Search: 340/52 R, 340/510, 340/540, 340/635, 340/636, 340/645, 340/646, 340/648, 340/650, 340/651, 340/653, 340/657, 320/48, 320/68
• US Class Current: 340/455
• CPC Class Codes: B60Q 11/00 Arrangement of monitoring devices for devices provided for in groups B60Q1/00 - B60Q9/00
• CPC Class Codes: H02J 2310/40 The network being an on-board power network, i.e. within a vehicle
• CPC Class Codes: H02J 7/0047 with monitoring or indicating devices or circuits
• CPC Class Codes: H02J 7/14 for charging batteries from dynamo-electric generators driven at varying speed, e.g. on vehicle

Abstract

An alarm circuit indicating a defect in a car alternator, said circuit comprising a voltage divider formed by two resistors connected between the positive terminal B+ and a negative terminal D- of the alternator, the center point of the voltage divider being connected to the control electrode of a commutation circuit of which the output path is serially connected with a lamp between the terminals of the battery, and rectifier means being provided for preventing the battery to discharge through the voltage divider.

Claims

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, and

a 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.

2. An alarm circuit according to claim 1 wherein said warning means is connected in series with the output path of said electrical commutation circuit for connection between said battery terminals.

3. An alarm circuit according to claim 1 wherein said voltage divider comprises a resistor voltage divider.

4. An alarm circuit according to claim 8 wherein said diode means comprises a first plurality of rectifying diodes which provide the rectified voltage output at said second alternator output terminal.

5. An alarm circuit according to claim 3 wherein said diode means also includes a second plurality of diodes which provide a rectified voltage output at said second auxiliary alternator terminal which is isolated from but substantially identical to the rectified voltage output provided at said second alternator output terminal.

6. An alarm circuit as claimed in claim 1, wherein means are connected to said control electrode for eliminating transient voltage variations.

7. An alarm circuit as claimed in claim 1, wherein said commutation means comprise a Darlington circuit having a base electrode connected to the center point of the voltage divider and a collector-emitter output path serially connected with said warning device.

8. An alarm circuit as claimed in claim 7, wherein a capacitor is connected between the base and the collector of the Darlington circuit.