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Self Test of Solenoids

IP.com Disclosure Number: IPCOM000045033D
Original Publication Date: 1983-Jan-01
Included in the Prior Art Database: 2005-Feb-06
Document File: 2 page(s) / 33K

Publishing Venue

IBM

Related People

Eichhorn, TF: AUTHOR [+2]

Abstract

A test circuit is described for a microprocessor-controlled machine employing controller-actuated solenoids.

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Self Test of Solenoids

A test circuit is described for a microprocessor-controlled machine employing controller-actuated solenoids.

With only one of the simple circuits shown in the figure, a microprocessor control can self test all of its solenoids. This test also verifies the proper operation of the drivers and continuity of cabling and connectors. Usage counters are also verified using this circuit without falsely incrementing the count. Since this test is always conducted as a part of a Power-On sequence, it provides an interlocking action that detects tampering with usage counters. Eliminating this tampering insures accurate information on machine performance and extent of usage.

The solenoids are wired so that all are coupled to a special solenoid load bus. When a solenoid is turned on, current flow through diodes CR1 and CR2 causes a voltage drop that turns on the transistor. Resistors R3 and R4 convert the collector current to a level compatible with the microprocessor input requirements. R-1 insures turn off when no current is flowing.

The microprocessor initially verifies that none of the outputs to the drivers is "on". It next checks whether the input from the current sensing circuit is in the "off" state. If it is not off, then a circuit failure is deemed to have occurred, an error code can be displayed, and the test is halted. Otherwise, the microprocessor sequences through the solenoids by turning them on one at a time, checking for current sense, a...