We found this circuit in the 1983 edition of the Electronics Experimenter handbook. The circuit uses components that are common today, although many admit equivalents.
Circuits similar to this appear elsewhere in this section. The transistors can be BC549 (low...
This circuit indicates when a rain is acidic by monitoring its pH. The circuit is from a 90s RE...
In a microprocessor project (shield) for control applications, a triggered clock can be useful....