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P.O. Box J CARMICHAEL, CA 95608 (916) 966-2111

DVM adapter for a frequency counter. This circuits consists of a 200 k-ohm/volt input low pass active filter stage, a polarity detector and automatic switcher/indicator, and a voltage-to-frequency converter. The output frequency is adjusted so that 50 vofts input will give a frequency of 5000 out. The three 25K pots are used for offset balancing. Any counter capable of readout to Hz is fine. Circuit by W0MLD.

ALL RESISTORS- l/SW

MOISTURE PHCTO

DETECTOR CELL

ALL RESISTORS- l/SW

Light dimmer which will handle up to 800 watts of incandescent lamps. 10 nF = .01 ¡JF, by the way. Circuit courtesy of Motorola Semiconductor Power Circuits Handbook.

Video amplifier using a HEP 590 IC, courtesy of Motorola.

MOISTURE PHCTO

DETECTOR CELL

Basic control unit vjhich can be used for almost anything . . . timer, light activated relay, moisture detector, etc. The timer circuit will range from about 5 seconds (o 50 seconds. Change i? and C to alter range. The moisture detector normally uses a small printed circuit board with interlaced v/ire network to allow moisture to bridge the contacts. Light relay operates vrhen light strikes the cell. Circuit courtesy Motorola HMA-33 Tips on using FETs.

C2 0 nF

+1 0

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