To cut the lag-lead in motor-driven timing devices, the timing circuit has been extended to include a second switch. This is actuated in time with the first but driven directly at a speed x times faster than the first

Rich, S.

English

NASA Technical Reports Server

Circuit 
iming Circuit 
N2	 N3
titjUITh 1 
N	 N	 N
FIGURE 2 
December 1964
	
Brief 63-10143 
NASA TECH BRIEF 
This NASA Tech Brief is issued by the Technology Utilization Division to acquaint 
industry with the technical content of an innovation derived from the space program. 
Coincident Switch Closing Reduces Error in Motor-Driven Timer 
The problem: Conventional motor-driven timing 
devices depend on a gear train to time a cam that 
closes and opens a switch. Because of the inherent lag-
lead nature of the last member of a gear train, the cam 
dwell angle is affected and the precise moment of 
switch closure varies in proportion to the lag-lead 
factor. 
The solution: The extension of the timing circuit 
to include a second switch actuated in time with the 
first but driven directly at a speed x times faster than 
the first.
How it's done: A conventional electromechanical 
timing device is shown in figure 1. In this configura-
tion, the switch closure variable can be expressed in 
terms of cam dwell angle e (the angular period during 
which the cam holds the switch closed) in degrees, or 
time (T = N 1 N 2N 3e/360A minutes) where: N1N2N3 
are the gear ratios. A is the speed in revolutions per 
minute of the drive motor. By extending the timing 
circuit to include an additional switch and cam as 
shown in figure 2, the timing error T is appreciably 
reduced. By synchronizing the cams so that switch I 
closes prior to a closure of switch 2 and remains closed 
(continued overleaf) 
This document was prepared under the sponsorship of the National 
Aeronautics and Space Administration. Neither the United States Govern. 
ment, nor NASA, nor any person acting on behalf of NASA: A. Makes 
any warranty or representation, express or implied, with respect to the 
accuracy, completeness, or usefulness of the information contained in
this document, or that the use of any information, apparatus, method, 
or process disclosed in this document may not infringe privately-owned 
rights; or B. Assumes any liabilities with respect to the use of, or for 
damages resulting from the use of, any information, apparatus, method, 
or process disclosed in this document.
	 -
https://ntrs.nasa.gov/search.jsp?R=19630000016 2020-03-11T16:45:00+00:00Z
during that closure of switch 2, the circuit closure 
variable is limited to that occurring in switch 2. This 
amounts to T = 0/360A minutes, the gear-train effect 
having been removed. Although switch 2 will close 
more times per unit time interval than switch I due to 
the effect of the gear train, overall timing function 
remains in switch I. 
Notes: 
1. This method could be used to provide precision 
timing over a range of intervals limited only by the 
availability of gear train configurations and drive 
motor speeds.
2. Inquiries concerning this innovation may be di-
rected to:
Technology Utilization Officer 
Jet Propulsion Laboratory 
4800 Oak Grove Drive 
Pasadena, California, 91103 
Reference: B63-10143 
Patent status: NASA encourages commercial use

of this innovation. No patent action is contemplated. 
Source: Samuel Rich
(JPL-182) 
Brief 63-10143	 Category No. 05


Coincident switch closing reduces error in motor-driven timer

Abstract

Similar works

Full text

Available Versions

NASA Technical Reports Server