Wiring harness diagnostic system
First Claim
1. A fault detection circuit for an electrical system having output transistors connected to a plurality of conductive lines for providing outputs over the lines to corresponding loads, the output transistors switchable between first and second states, wherein in the second states, the output transistors are in an on condition and in saturation with a low collector to emitter voltage (Vce) when the lines are properly connected to the output load, the fault detection circuit comprising:
- a sensing circuit connected to the output lines;
a control circuit for selectively switching the transistors to the second state; and
wherein the sensing circuit is responsive to presence and absence of the low Vce indicative of the saturated condition when the second state is selected to provide an indication if the lines are improperly connected.
1 Assignment
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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
19 Claims
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1. A fault detection circuit for an electrical system having output transistors connected to a plurality of conductive lines for providing outputs over the lines to corresponding loads, the output transistors switchable between first and second states, wherein in the second states, the output transistors are in an on condition and in saturation with a low collector to emitter voltage (Vce) when the lines are properly connected to the output load, the fault detection circuit comprising:
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a sensing circuit connected to the output lines;
a control circuit for selectively switching the transistors to the second state; and
wherein the sensing circuit is responsive to presence and absence of the low Vce indicative of the saturated condition when the second state is selected to provide an indication if the lines are improperly connected. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A fault detection circuit for an electrical system on a vehicle, the vehicle having a plurality of conditions to be monitored, the detection circuit including switchable output transistors connected to a plurality of conductive lines for providing outputs over the lines to corresponding loads, the output transistors having first and second states, wherein in the second states the output transistors are in an on condition to drive the the loads and wherein when the loads are properly connected to the output transistors the output transistors are in saturation and have a low collector to emitter voltage (Vce);
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a sensing circuit connected to the output lines and responsive to presence and absence of the low Vce when the transistors are in the on condition for providing a fault indication if the low Vce condition is absent;
a controller connected to the output transistors for switching the output transistors to the on condition; and
indicators connected between the controller and the output transistors and providing an indication of the lines over which outputs are to be provided, the indicators facilitating visual correlation of the conditions to be monitored with the output lines. - View Dependent Claims (12, 13, 14, 15)
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16. A fault detection system for connecting lines of an operational electrical circuit presenting a preselected current load, the circuit including an output transistor with an output terminal having an on and an off condition and connected to the current load;
- the fault detection system including;
a controller connected to the transistor circuit for selectively changing the condition of the output transistor;
wherein the voltage on the output terminal is a first level when the output transistor is in the on condition and the current load is less than or equal to the preselected current load when the output transistor is in saturation, and the voltage is offset from the first level when the transistor is in the on condition and the current load is greater than the preselected current load wherein the output transistor is not in saturation;
a check circuit connected to the controller and the output line and responsive to the voltage on the output line; and
wherein the check circuit provides a fault signal to the controller in response to the voltage on the output line being offset from the first level so that the fault signal is responsive to output transistor saturation. - View Dependent Claims (17, 18, 19)
- the fault detection system including;
Specification