Control circuit for bill and coin changer

Abstract

A bill and coin changer in which a circuit employing a programmed microcomputer controls the bill-validating and coin-dispensing procedures and searches for faults in the operation of the sensors and electromechanical components of the changer. During bill validation, a bill is moved at a predetermined speed along a path past a plurality of sensors, and rejection signals are generated if a particular sensor is actuated for other than a predetermined permissible duration or generates a predetermined output within a test period delimited by the delayed output of the other sensors. In response to a rejection signal, the bill is returned to the customer and a diagnostic hexadecimal rejection code character is displayed indicating the condition prompting rejection. Jammed objects are extricated from the bill transport by alternatingly actuating the transport to move the object in one direction and then in the other upon sensing a jammed condition. When not engaged in a validating or coin-dispensing sequence, the control circuit sequentially interrogates in cyclical fashion a plurality of lines coupled to those sensors which should not be actuated during a quiescent period. If one of the lines is found to be erroneously actuated, the control circuit inhibits further acceptance of bills or coins and displays a diagnostic hexadecimal fault code character indicating the nature of the fault. The control circuit resumes normal operation if the fault does not involve an electromechanical component and later corrects itself. Failure of an electromechanical component or dispensing of an erroneous amount of change causes the power supply lines energizing these components to be disabled.