This circuit indicates when a rain is acidic by monitoring its pH. The circuit is from a 90s RE Experimenter Handbook. Some components used can be difficult to obtain today.
This circuit emits a sound at regular intervals to prevent you from falling asleep, for example. It...
November 2016 - Texas Instruments' new TLV8802 nano-power operational amplifiers for wireless...
The circuit presented is from 1994 and can be implemented with more modern equivalent components. We...