Device satisfies 1-sec, 5-sec, and 10-min timing requirements. Temperature and voltage range accuracy is plus or minus 3.9 percent with voltage variations of 24 to 31 Vdc over temperature range of minus 55 deg C to plus 125 deg C

Gulbis, P. R.

English

NASA Technical Reports Server

Power In 
mi
November 1971
	 Brief 71-10437 
S
NASA TECH BRIEF 
Marshall Space Flight Center 
NASA Tech Briefs announce new technology derived from the U.S. space program. They are issued to encourage 
commercial application. Tech Briefs are available on a subscription basis from the National Technical Information 
Service, Springfield, Virginia 22151. Requests for individual copies or questions relating to the Tech Brief program may 
be directed to the Technology Utilization Office, NASA, Code KT, Washington, D.C. 20546. 
Externally Programmed Variable Timer 
A unique timing device, developed to satisfy 
1-see, 5-see, and 10-min timing requirements, in-
corporates external programming capability. 
Programmable Timer Block Diagram 
Operational efficiency of 5% over a tempera-
ture range of —65°C to + 130°C was a design re-
quirement. To reduce the effect of temperature 
on the programmable timer, the time constant of 
the unijunction transistor (UJT) oscillator (see fig.) 
was reduced and the oscillator frequency was di-
vided by using bistable multivibrators (flip-flops). 
This limited the temperature sensitivity of the 
timer to that of the UJT oscillator. 
The number of flip-flops used at any given time 
is programmed by interconnecting the desired num-
ber of available inputs and outputs. The universal 
timer can divide the output frequency of the UJT
oscillator by 2, 4, 8, 16, 32, 64, or 128. Output of 
the final flip-flop is connected to a pulse generator 
circuit that produces a 28 V, 50 msec pulse. This 
output is routed back to a start-reset circuit that 
controls the UJT relaxation oscillator and the flip-
flops. 
Temperature and voltage range tests resulted in 
ail accuracy of ± 3.9% with supply voltage varia-
tions of 24 to 31 Vdc over the temperature range 
of —55°C to +125'C. The programmable timer was 
within the ± 5% efficiency over the required tem-
perature range with the same supply voltage regula-
tion. 
Note: 
Requests for further information may be directed 
to:
Technology Utilization Officer 
Code A&TS-TU 
Marshall Space Flight Center 
Huntsville, Alabama 35812 
Reference: TSP7I-10437 
Patent status: 
No patent action is contemplated by NASA. 
Source: P.R. Gulbis of

Sperry Rand

under contract to

Marshall Space Flight Center

(M FS-20776) 
Category 04 
This documefct was prepared under the sponsorship of the National 	 Government assumes any liability resulting from the use of the 
Aeronautics and Space Administration. Neither the United States 	 information contained in this document, or warrants that such use 
Government nor any person acting on behalf of the United States 	 will be free from privately owned rights.
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Externally programmed variable timer

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