Apparatus and method for testing printed circuit boards and their components

An apparatus for testing electrical circuits and components in them, comprising:

• a microcomputer having at least a microprocessor, input and output means, memory, and data, control, and address busses;
• a controller in electrical connection with said microcomputer and with access points of said circuit under test, said controller receiving digital test data from said microcomputer for determining values of a high rail reference voltage, a low rail reference voltage, a high threshold reference voltage, and a low threshold reference voltage and having digital to analog converters for converting said digital test data into said high rail reference voltage, low rail reference voltage, high threshold reference voltage, and low threshold reference voltage;
• a primary power supply in electrical connection with an AC source, with said controller, and with points of said circuit under test, said primary power supply receiving said top rail reference voltage and said low rail reference voltage from said controller and delivering a high rail voltage and a low rail voltage to said access points;
• a unit under test power supply in electrical connection with an AC source and with said circuit under test, said unit under test power supply delivering power to said circuit under test;
• a plurality of driving circuits in electrical connection with said microcomputer, with said high rail voltage, and with said low rail voltage, and with said access points, said driving circuit having means for delivering voltage to said access points at a high or low state corresponding to said high rail voltage and to said low rail voltage;
• a plurality of sensing circuits in electrical connection with said microcomputer, with said access points, and with said controller, said sensing circuits receiving said high threshold reference voltage and said low threshold reference voltage from said controller and having means for comparing said threshold reference voltages to output at said access points, said sensing circuits being in communication with said microcomputer so that the output from said sensing circuits may be delivered to said microcomputer for use;
• a control unit in electrical connection with said controller and with said driving and said sensing circuits, said control unit having at least:
• means for connecting said driving circuits to said access points so that a number of said access points are each in electrical connection with one of said driving circuits, and
• means for connecting said sensing circuits to said access points so that a number of said access points are each in electrical connection with one of said sensing circuits.

A method for testing a circuit having electrical components, with aid of a microcomputer, comprising the steps of:

• providing a data base to said microcomputer, said data base including at least:
• input access points and output access points of a known to be good model component, and
• values representing inputs and outputs of said model component;
• connecting pins for driving and sensing to said access points on one of said components under test, while said component is in-circuit;
• driving inputs of said component under test to a desired state at access points that correspond to input points of said model components;
• sensing outputs of said component under test at points that correspond to output points of said model component;
• comparing outputs of said component under test with said model;
• electronically communicating the results of said comparison to said microcomputer;
• displaying said results on a display means of said microcomputer;
• and
• repeating said steps until a number of said components in said circuit have been tested.

A method for learning the characteristics of a circuit having electrical components, by testing said circuit and its components, with aid of a microcomputer, comprising the steps of:

• providing a data base to said microcomputer, said data base including at least:
• input access points and output access points of a known to be good model component, and
• values representing inputs and outputs of said model component;
• connecting pins for driving and sensing to said access points on one of said components under test, while said component is in-circuit;
• driving inputs of said component under test to a desired state at access points that correspond to input points of said model components;
• sensing outputs of said component under test at points that correspond to output points of said model component;
• comparing outputs of said component under test with said model;
• electronically communicating the results of said comparison to said microcomputer;
• modifying said model in said data base to correspond with said sensed outputs;
• and
• repeating said steps until a desired number of components have been tested.

A method for learning the interconnections among components of an electrical circuit, using a microcomputer, comprising the steps of:

• providing a data base to said microcomputer, said data base comprising:
• identification of each of said components whose interconnections are to be learned, and
• identification of access points of each of said components;
• connecting pins for driving and sensing to access points of a reference component;
• connecting pins for driving and sensing to access points of a first target component;
• successively testing to determine whether short circuits exist between said access points of said reference component and said access points of said target component;
• disconnecting said first target component and repeating said steps with a next target component;
• and
• disconnecting said reference component and repeating said steps with a next reference component.