Reduction of retardation by diode-resistor networks of the current-decay time of a punch magnet by connection of a Zener diode in series with the damping network increases the reliability of data on paper tape

Cohn, C. E.

English

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September 1969	 Brief 69-10416 
•
ICY
AEC-NASA TECH BRIEF 
rES
AEC-NASA Tech Briefs describe innovations resulting from the research and development program 
of the U.S. AEC or from AEC-NASA interagency efforts. They are issued to encourage commercial 
application. Tech Briefs are published by NASA and may be purchased, at 15 cents each, from 
the Clearinghouse for Federal Scientific and Technical Information, Springfield, Virginia 22151. 
Punch-Magnet Delay Eliminated by Modification of Circuit 
- 
Existing 
Driver
Fig. 1. Modification when a Breakdown Margin Exists 
The problem: 
To increase the reliability of data on paper tape by 
modification of punch-magnet circuitry. Voltage-
damping-diode or diode-resistor networks have been 
used in the past to protect punch-magnet driver 
transistors from damage by inductive transients. 
These damping networks prolonged activation of 
the magnet by allowing current to remain in it after 
the driver transistor was turned off; thus the magnet 
operated improperly. 
The solution: 
Reduction of retardation, by the diode-resistor 
networks, of the current-decay time of the punch 
magnet by connection of a zener diode in series with 
the damping network.
How it's done: 
In a magnet driver circuit in which a voltage mar-
gin exists between the driver-transistor breakdown 
voltage and the circuit-supply voltage, a 24-V zener 
diode is connected in series with the damping net-
work (Fig. 1). Thus the network is effective only 
when the amplitude of the transient voltage exceeds 
24 V. Also a resistive-capactive network is added in 
series with the magnet coil, as recommended by the 
punch manufacturer. 
Notes: 
I. For punch-driver circuits having no voltage 
margin, another modification adds an extra magnet-
driver stage (Fig. 2).
(continued overleaf) 
Now
This document was prepared under the sponsorship of the Atomic 
Energy Commission and/or the National Aeronautics and Space 
Administration. Neither the United States Government nor any per-
son acting on behalf of the United States Government assumes any
liability resulting from the use of the information contained in this 
document, or warrants that the use of any information, apparatus, 
method, or process disclosed in this document may not infringe pri-
vately ownedrights.
https://ntrs.nasa.gov/search.jsp?R=19690000409 2020-03-16T18:16:19+00:00Z
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ded 
2. Inquiries may be directed to: 
Office of Industrial Cooperation 
Argonne National Laboratory 
9700 South Cass Avenue 
Argonne, Illinois 60439 
Reference: B69-10416
Source: C. E. Cohn
Reactor Physics Division

(ARG- 10333) 
To Remaining Damping
Networks
Patent status: 
Inquiries concerning rights for commercial use of 
this innovation may be made to: 
Mr. George H. Lee, Chief 
Chicago Patent Group 
U.S. Atomic Energy Commission 
Chicago Operations Office 
9800 South Cass Avenue 
Argonne, Illinois 60439 
----J 
Existing 
Driver
Fig. 2. Modification in the Absence of a Breakdown Margin 
Brief 69-10416	 Category 01


Punch-magnet delay eliminated by modification of circuit

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