Wiring harness diagnostic system
First Claim
1. A detection circuit for an electrical system on a vehicle, the vehicle having input structure monitoring a plurality of conditions on the vehicle during start-up and operation of the vehicle, the detection circuit including:
- output lines connected to a plurality of electrical loads;
a controllable drive circuit connected to the output lines for selectively providing drive of preselected amplitudes to the electrical loads;
a sensing circuit connected to the output lines and providing an output signal responsive to presence and absence of the drives of preselected amplitudes to the loads during the start-up and operation of the vehicle;
a controller connected to the drive circuit and selectively controlling the drive to the electrical loads, the controller also connected to the input structure and to the sensing circuit and providing a preselected response to the conditions on the vehicle and the output signal; and
a readout device connected to the controller and providing an error signal when the controller response fails to correspond to the preselected response.
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Accused Products
Abstract
A circuit includes a plurality of inexpensive resistors connected at one end to the open collector outputs of an output array of NPN output transistors which are connected to a wiring harness or the like for selectively powering a preselected load. The opposite ends of the resistors are connected to the base of an NPN sense transistor. The output NPN transistors, when in the on condition, are biased well into saturation for normal loads and therefore provide a very low Vce (sat) when properly connected through the harness to the intended load. In the off condition, the output NPN transistors look essentially like an open circuit. Vce (sat) is lower than the base turn-on voltage of the NPN sense transistor which has a grounded emitter. The collector of the NPN sense transistor is connected to a source of voltage through a pull-up resistor and to an input of the microprocessor which controls the signals to the output array transistors. The base of each output transistor is connected to an LED to provide a visual indication of which inputs are on and to help the technician locate an area on the circuit board or wiring harness corresponding to a particular function or load on the vehicle.
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Citations
14 Claims
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1. A detection circuit for an electrical system on a vehicle, the vehicle having input structure monitoring a plurality of conditions on the vehicle during start-up and operation of the vehicle, the detection circuit including:
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output lines connected to a plurality of electrical loads;
a controllable drive circuit connected to the output lines for selectively providing drive of preselected amplitudes to the electrical loads;
a sensing circuit connected to the output lines and providing an output signal responsive to presence and absence of the drives of preselected amplitudes to the loads during the start-up and operation of the vehicle;
a controller connected to the drive circuit and selectively controlling the drive to the electrical loads, the controller also connected to the input structure and to the sensing circuit and providing a preselected response to the conditions on the vehicle and the output signal; and
a readout device connected to the controller and providing an error signal when the controller response fails to correspond to the preselected response. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A method of providing an error indication to an operator of a vehicle, the vehicle having a plurality of electrical load devices for controlling operations of the vehicle, a controller with controller input device receiving signals from input devices on the vehicle including an input for connection to an interlock circuit responsive to conditions on the vehicle, and a driver having output terminals providing control outputs, the output terminals connected by wiring structure to the controller and to the electrical load devices, the method including the steps of:
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activating the driver with the controller in accordance with preselected conditions on the vehicle;
monitoring output signals from the output terminals;
comparing the monitored output signals from the output terminals with a desired response including a desired amplitude of the control outputs for preselected conditions on the vehicle;
preventing operation of the vehicle if the monitored output signals deviate from the desired response; and
providing an indication to the operator of the fault which is preventing operation of the vehicle so the operator can determine immediately the conditions causing the prevention of operation. - View Dependent Claims (10, 14)
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11. A method of providing an error indication to an operator of a vehicle, the vehicle having a plurality of electrical load devices for controlling operations of the vehicle, a controller with controller input device receiving signals from input devices on the vehicle including an input for connection to an interlock circuit responsive to conditions on the vehicle, and a driver having output terminals providing control outputs, the output terminals connected by wiring structure to the controller and to the electrical load devices, the method including the steps of:
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activating the driver with the controller in accordance with preselected conditions on the vehicle during start-up and operation of the vehicle;
monitoring output signals from the output terminals;
comparing the monitored output signals from the output terminals with a desired response for preselected conditions on the vehicle during the start-up and operation;
preventing operation of the vehicle if the monitored output signals deviate from the desired response;
providing an indication to the operator of the fault which is preventing operation of the vehicle so the operator can determine immediately the conditions causing the prevention of operation; and
further comprising the step of identifying portions of the controller and the driver associated with conditions to which the interlock circuit is responsive without need for a circuit diagram by inserting a signal device between the controller and driver, and activating the signal device by changing a particular condition of the interlock circuit. - View Dependent Claims (12, 13)
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Specification