Browse Prior Art Database

Coil Current Detection Method

IP.com Disclosure Number: IPCOM000102746D
Original Publication Date: 1990-Jan-01
Included in the Prior Art Database: 2005-Mar-17
Document File: 1 page(s) / 47K

Publishing Venue

IBM

Related People

Logan, TD: AUTHOR

Abstract

Disclosed is a method for visual determination that a magnetic coil is actually energized by input pulses. This is accomplished by connecting a LED (Light Emitting Diode) in the magnet drive circuit in such manner that it is lit by the voltage generated by the collapsing magnetic field when the input pulse terminates. If the coil circuit is open, it is not energized, there is no field developed, and the LED does not light.

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Coil Current Detection Method

      Disclosed is a method for visual determination that a magnetic
coil is actually energized by input pulses. This is accomplished by
connecting a LED (Light Emitting Diode) in the magnet drive circuit
in such manner that it is lit by the voltage generated by the
collapsing magnetic field when the input pulse terminates. If the
coil circuit is open, it is not energized, there is no field
developed, and the LED does not light.

      The present embodiment is a tester for the print hammer unit of
a known printer. The Figure is a schematic diagram of the circuit
into which each print hammer coil is connected by the tester. (This
circuit duplicates the hammer coil waveform applied by the printer
itself.) It is apparent that the hammer coil is energized when both
transistors Q1 an Q2 are in the ON state. It is also seen that at
this time there is no current flow through the LED as the collector
of Q2 is held at a low voltage level.  When Q1 and Q2 are both
turned OFF, opening the hammer coil energizing circuit, the coil
field collapses generating an inductive voltage that is dissipated
through the loop formed by diodes D1 and D2. It is seen that at this
time the voltage of Q2 collector  rises to a high level. This voltage
applied across the LED, and its series resistor R, lights the LED,
which is visible to the test operator.

      Characteristics of this circuit provide the tester with a
degree of failure self detection. If Q2 ha...