This simple continuity tester, whose configuration can be found several times on this site, is powered by only 2 batteries providing the indication on an LED.
The operational amplifier used in this project no longer exists, but the circuit can be adapted to...
With S1 closed, when dark, the triac will supply the load with the power set in R4. The LDR is...
Toshiba LDO Regulators Toshiba has a wide variety of low voltage drop (LDO) linear regulators...