Monday Kids Ticking Clock Sound Effect Circuit DIY Kits

this is a low frequency oscillation circuit that the frequency is about 1Hz. That means it oscillates one time per second. When press down the button switch, the electrolytic capacitor,C1 is charging, and V1 is conducted and then V2 is conducted and then V3 is conducted, and then V4 is conducted finally. However, the conducted state of V4 won’t last long, actually it is instant. Because when V4 is conducted, the voltage of the anode side of C2 is dropping down to about 0V rapidly that causes the voltage of the other side of C2 falls down to about 0V rapidly, the NPN transistor, V3 is cut-off. But in the meantime, the side of C2 connected to the base of V3 starts charging and for about 1 second the accumulated voltage reaches the bias voltage of the transistor, the V3 conducts again. These processes repeat again and again that generating the 1Hz signal to drive the speaker to make a timer sound.