A simple interval timer for non-clockwatchers

BEHAVIOR THERAPY 8, 487--488 (1977)

INSTRUMENTATION AND TECHNIQUES A Simple Interval Timer for Non-Clockwatchers GORDON D. H A N S E N University of Nebraska at Omaha An inexpensive and easily constructed device to indicate set intervals of time with an unobtrusive light and auditory signal is described that allows experimenters the opportunity to devote their undivided attention to the object of their research.

Many experimenters have been plagued with the problem of timesampling studies within which one must attend carefully to a stimulus situation so as to note specific behaviors at preset, rather short intervals of time. The device described within this article was the result of a plea for help from a psychologist who was doing research for an improvement of instruction committee. She needed to observe, at 3-sec intervals, certain types of instructional behavior being emitted without the interference of attending to a stopwatch. Since the completion of the original unit, it has become necessary to construct three more units for others in the department with similar needs who had become aware of its existence. The device consists of a light-emitting diode (LED), a small speaker or earphone, and an adjustable control. While observing the behavior in question, the experimenter's peripheral vision is stimulated by the LED at the same time that a low-intensity sound is emitted, signaling that the preset interval of time has elapsed. The circuit (Fig. 1) utilizes a single NPN general purpose silicon transistor powered by a standard 9-V transistor battery that, due to low current consumption, will last for at least a year under regular use. Some slight variation in the time interval indicated will occur as a function of changes in battery voltage and the stability of a RC circuit. This variation is of no consequence for most applications, and Requests for reprints should be addressed to the author, Psychology Department, University of Nebraska at Omaha, Box 688, Omaha, NE 68101. 487 Copyright © 1977by the Association for Advancement of Behavior Therapy. All rights of reproduction in any form reserved.

ISSN 0005-7894

488

INSTRUMENTATION AND TECHNIQUES

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10K ~ W resistor 1 meg variable control 0.022 mfd capacitor 100 mfd@ 16 V 0.22 mfd capacitor Light-emitting diode 1.75 v @ 20 mA NPN low noise, high gain amp Out transformer 1000-ohm primary 8-ohm secondary 8-ohm speaker SPST switch

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271-000 271-211 272-1066 272-1005 272-1070

RS 276-041 RS 276-2010 RS 273-1380 RS 40-245 RS 23-464

Like components from other manufacturers may be substituted. All parts are available from: Radio Shack, 2617 West 7th Street, Fort Worth, TX 76107.

the interval of time m a y be adjusted from a frequency o f o n c e every 45 sec to o n c e per second. The device m a y be easily constructed within a plastic soap dish or similar container for a total cost o f less than $10.00. RECEIVED" March 12, 1976; REVISED: June 24, 1976 FINAL ACCEPTANCE: September 17, 1976