Electronic Grandfather Clock
Do you want to perk up the ears of some of your elders? Anyone who has lived in a house with a grandfather clock will think you have one when they hear this project. The clicks obtained by this pulse-oscillator circuit are about a second apart. (Change the 100K Resistor to obtain faster or slower pulse rate.)
The timing and sound together are what give the listener the mental picture of the old grandfather clock. The steady monotonous ticking has also been used to stimulate animals and people into a restful state of mind. Anyone who has traveled by train and heard the click, click, click of the tracks knows how easy it is to fall asleep under these conditions. Hypnotists have long used this hypnotizing characteristic to gain control of their subject's mind.
We've described circuit operation elsewhere in Oscillator Section so we won't go into great detail.
1. When power is first applied, the 100K starts the Transistor into conduction.
2. The 100uF quickly charges up to a voltage greater than the 3V Batteries, due to induced voltage in the transformer windings.
3. When the Transformer core reaches magnetic saturation, the induced voltage decreases, allowing the 100uF charge to quickly cut off the Transistor (due to reverse base-bias).
4. The 100uF must now slowly leak its charge off through the 100K and Battery until its voltage about equals that of the Battery.
5. When the 100uF voltage about equals that of the Battery, the Transistor can conduct again for a short time, and that's when you hear the click (as the Transistor conducts and the Capacitor receives a charge).
Now, you want to scare this "clock" into stopping. Yell into the speaker. How about that?
You can momentarily stop this clock. Can you explain why?
Here is a a other version