We have many versions of biofeedback with the 555 IC on this site. This is another one. We found it in October 1986 Radio Radio Electronics magazine. The power supply must be isolated.
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....