This circuit detects smoke by changing the light falling on the sensor. The circuit was found in the Electronics Experimenter's Handbook of 1991. Optical devices must be used.
We found this common application of the 741 operational amplifier in a 1977 documentation. The...
This circuit, found in an old 1967 publication, cuts the current from a source when the current...
This LED bar graph circuit was found in the October 1980 issue of Radio Electronics magazine. The...