Browse Prior Art Database

Magnet Driver and Pulse Width Controller

IP.com Disclosure Number: IPCOM000092136D
Original Publication Date: 1968-Sep-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 2 page(s) / 39K

Publishing Venue

IBM

Related People

Melnyk, G: AUTHOR

Abstract

This pulse circuit, for print hammer magnets and like devices, senses a decrease in current at the time the armature begins to close and thus terminates the drive. Transistor T1 and T2 form a latch and, in normal state, T1 is on. The collector at T1 is biased at one volt which is insufficient to forward bias D3 and D4 sufficiently to turn T2 on. Since T2 is turned off, T3 and T4 are also off. A negative-going pulse applied to the base of T1 via C1 turns T1 off. When T1 is turned off, T2, T3, and T4 are turned on and current begins to rise in solenoid coil 1. The voltage across R9 begins to charge C2 through D1. When the armature of the solenoid begins to move, the voltage across R9 tends to decrease. The voltage across C2 now forward biases the emitter-base junction of T1 turning it on.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 100% of the total text.

Page 1 of 2

Magnet Driver and Pulse Width Controller

This pulse circuit, for print hammer magnets and like devices, senses a decrease in current at the time the armature begins to close and thus terminates the drive. Transistor T1 and T2 form a latch and, in normal state, T1 is on. The collector at T1 is biased at one volt which is insufficient to forward bias D3 and D4 sufficiently to turn T2 on. Since T2 is turned off, T3 and T4 are also off. A negative-going pulse applied to the base of T1 via C1 turns T1 off. When T1 is turned off, T2, T3, and T4 are turned on and current begins to rise in solenoid coil
1. The voltage across R9 begins to charge C2 through D1. When the armature of the solenoid begins to move, the voltage across R9 tends to decrease. The voltage across C2 now forward biases the emitter-base junction of T1 turning it on. The base of T1 is effectively hold near ground potential through forward biased D2 and T2 which is turned on at this time. T1 in turning on turns off T2, T3, and T4 restoring the circuit to its latched state.

1

Page 2 of 2

2

[This page contains 2 pictures or other non-text objects]