Solar flashlight (CB20488E)

This circuit charges a battery to power a flashlight at night. The circuit is from an English publication from 1991.

Time Constant Multiplier (CB19498E)
This circuit multiplies a time constant given by the input components. The circuit admits...
Industrial alarm (CB23560E)
This circuit is nothing more than a powerful audio oscillator or buzzer with a power transistor. The...
Variable Frequency Ring Oscillator (CIR113E)
An way to change the frequency of the previous oscillator (CIR112E) is to add a variable capacitor in the...