Found in a1967 Ferranti documentation, this circuit uses an operational amplifier from that time. The circuit uses a LDR as a sensor and has a null setting.
The circuit below was found in the March 1990 issue of Radio Electronics magazine. The circuit...
The circuit shown in the figure causes the lamp to light up after a certain time determined by the...
This circuit uses a selector switch to select resistors for timings given in seconds. Capacitor C1 can be...