We found this circuit in the Encyclopedia of Electronic Circuits Volume 5 from 1995. It uses a 3-terminal transducer from the time. The circuit is triggered by light.
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....