This circuit uses an unusual sensor nowadays, but the configuration can be adapted to more modern types, as well as the operational amplifier. The circuit is from an 80's documentation.
This circuit, obtained from old documentation, doubles the frequency of the pulses applied to the...
The passage of an object in front of the LDR, producing a shadow or even turning off the ambient...
The CMOS TLC555 [equivalent to the bipolar 555] can be used as a monostable in the configuration...