Sometime ago, I noticed that the newer wall clocks we bought seem to deplete the batteries quite quickly. Whereas before when we plug a fresh AA battery, it takes almost two years before we have to replace the battery. Now, the charge lasts less than a year. I checked some of the batteries I have not thrown away and was surprised that there is still power left in the batteries.
Now the normal voltage for a fresh AA 1,5volt batteries is about 1.7volts. Those used ones I have saved is about 1.4-1.5 volts. Still within the nominal range of its rating. It led me to wonder how come it cannot power the newer wall clocks? I also noticed that those clocks we bought are all China made. In the past I have dismantled a few of the China made clocks to see what makes it work. I found there is a sort of electromagnet inside which provides pulses to a small central magnet to make it rotate a few degrees each pulse. This magnet rotates the second-hand of the clock and through various gear linkages, ultimately rotates the minute and hour-hands of the clock.
My theory is that since these are China-made, which we have to accept that although quite cheap, were not of the highest quality, the electromagnet coil turns must have been reduced to reduce cost. The effect is that when the battery voltage falls down a bit, not enough current flows to the electromagnet to sufficiently pulse rotate the central magnet. That is just my theory and cannot be proved.
Anyway since I have started experimenting with switched booster circuits in connection with my PMG project, it would be nice to find a way to use whatever I have learned to prolong the life of the batteries. It would be nice to save some money from always purchasing new AA batteries and at the same time help the environment since in a small way I can help reduce the amount of old batteries just thrown away when there is still some useful life left on them.
The project is still simple although it still took me several days to design, test in a breadboard, and then solder the components. The project circuit boosts the battery voltage about 10X which is more than enough to power the clock. I used a zener diode to clamp the output voltage to about 3 volts. I also found that too high voltage will not work also. 3 volts is about OK I think. The circuit is a free form one since I did not use any circuit board. And also quite tiny. See picture of the circuit prior to installment in the clock below.
Now the normal voltage for a fresh AA 1,5volt batteries is about 1.7volts. Those used ones I have saved is about 1.4-1.5 volts. Still within the nominal range of its rating. It led me to wonder how come it cannot power the newer wall clocks? I also noticed that those clocks we bought are all China made. In the past I have dismantled a few of the China made clocks to see what makes it work. I found there is a sort of electromagnet inside which provides pulses to a small central magnet to make it rotate a few degrees each pulse. This magnet rotates the second-hand of the clock and through various gear linkages, ultimately rotates the minute and hour-hands of the clock.
My theory is that since these are China-made, which we have to accept that although quite cheap, were not of the highest quality, the electromagnet coil turns must have been reduced to reduce cost. The effect is that when the battery voltage falls down a bit, not enough current flows to the electromagnet to sufficiently pulse rotate the central magnet. That is just my theory and cannot be proved.
Anyway since I have started experimenting with switched booster circuits in connection with my PMG project, it would be nice to find a way to use whatever I have learned to prolong the life of the batteries. It would be nice to save some money from always purchasing new AA batteries and at the same time help the environment since in a small way I can help reduce the amount of old batteries just thrown away when there is still some useful life left on them.
The project is still simple although it still took me several days to design, test in a breadboard, and then solder the components. The project circuit boosts the battery voltage about 10X which is more than enough to power the clock. I used a zener diode to clamp the output voltage to about 3 volts. I also found that too high voltage will not work also. 3 volts is about OK I think. The circuit is a free form one since I did not use any circuit board. And also quite tiny. See picture of the circuit prior to installment in the clock below.
Another picture below shows the circuit installed in the clock. Then the following video shows the circuit in action.
Since the voltage is boosted 10 times, even if the battery goes down to 0.5 volts, it can still adequately power the clock.