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Detailed entries for one subject from the INDEX TO HOW TO DO IT INFORMATION.
Click on a see also (sa) or tracing (xx) to view detailed entries about a related subject.
The entries are in alphabetical order by magazine name and then in chronological sequence.
To obtain a copy of any magazine article contact your local public library or the publisher.


A simple liquid-level indicator for the blind.
POPULAR ELECTRONICS [1] Apr 1981 (v.19#4) pg. 96

Monostable circuit uses a capacitive transducer to measure the level of water in a sealed container.
POPULAR ELECTRONICS [2] Jan 1990 (v.7#1) pg. 23

Full-cup detector circuit will tell a blind person when a coffee cup is full.
POPULAR ELECTRONICS [2] Mar 1990 (v.7#3) pg. 24

Latching water sensor circuit activates a relay. Use as a fill-level monitor, sump pump switch, rain sensor, etc.
POPULAR ELECTRONICS [2] Nov 1990 (v.7#11) pg. 22

Electronic aids for the blind. (1) Liquid-level indicator for a cup or glass. (2) Light probe turns light into sound.
POPULAR ELECTRONICS [2] Jan 1991 (v.8#1) pg. 27

Using a single special-purpose IC (the ULN2429A fluid detector) in as many applications as possible. (1) Low-level liquid level detector. (2) High-level liquid level detector. (3) Touch-activated switch. (4) Proximity sensor. (5) Ultrasonic pest repeller. (6) Variable square-wave generator. (7) Code-practice oscillator. (8) Alarm circuit. (9) Light beam circuit (LED-emitter / phototransistor-sensor circuit).
POPULAR ELECTRONICS [2] Jun 1994 (v.11#6) pg. 76

Circuits for a liquid-level detector built around the Sprague ULN-2429A IC.
RADIO-ELECTRONICS Feb 1988 (v.59#2) pg. 75

Liquid-level detector circuit to turn on a sewage pump automatically. Both non-latching and latching circuits shown.
RADIO-ELECTRONICS Nov 1989 (v.60#11) pg. 12
Added Info RADIO-ELECTRONICS Jan 1990 (v.61#1) pg. 16