Nautica Rick
New Member
I have a small project I've started and need some help with a very basic circuit. I am a fishing fanatic and reliable DC powered aerators are simply not available. I decided to convert an inexpensive AC fish tank aerator to DC. My first thought was to add a DC motor to drive the diaphragm pump, but a little thinking sent me in a different direction.
The AC pump motor consists of a small coil about 3/4" cubic. This is mounted on a magnetized iron core that is U-shaped. One arm of the U goes through the center and the other is on the side. Parallel to the face of the iron core, where it exits the top of the coil, is a magnet mounted on the end of a steel blade. The other end of the blade is mounted in rubber. When the pump is plugged in, the changing polarity of the magnetic field moves the magnet between the two arms of the iron core. This in turn moves the blade back and forth and the diaphragm pump is mounted in the middle of the blade and developes about a 2mm stroke.
I looked for micro inverters that I could rob the innards from and simply power the existing motor with batteries. Since the unit only consumes 1.5 watts, the smallest and cheapest inverters I could find were 50-100 times larger than I needed. This started me thinking further. An osillator in its simplest form is an inductor and a capacitor. Making a steel blade physically ocscillate does not require a clean, stable or precise signal. With the proper capacitor across the coil and a few D cells to power the unit, I would think this simple device would work quite well.
This is where all my thinking gets me into trouble. How do I size the capacitor? Would I need any other components? Am I about to set the house on fire? It's been about 25 years since I made a living in electronics, so I'm a little rusty. Any help you guys could offer on this project would really be appreciated.
The AC pump motor consists of a small coil about 3/4" cubic. This is mounted on a magnetized iron core that is U-shaped. One arm of the U goes through the center and the other is on the side. Parallel to the face of the iron core, where it exits the top of the coil, is a magnet mounted on the end of a steel blade. The other end of the blade is mounted in rubber. When the pump is plugged in, the changing polarity of the magnetic field moves the magnet between the two arms of the iron core. This in turn moves the blade back and forth and the diaphragm pump is mounted in the middle of the blade and developes about a 2mm stroke.
I looked for micro inverters that I could rob the innards from and simply power the existing motor with batteries. Since the unit only consumes 1.5 watts, the smallest and cheapest inverters I could find were 50-100 times larger than I needed. This started me thinking further. An osillator in its simplest form is an inductor and a capacitor. Making a steel blade physically ocscillate does not require a clean, stable or precise signal. With the proper capacitor across the coil and a few D cells to power the unit, I would think this simple device would work quite well.
This is where all my thinking gets me into trouble. How do I size the capacitor? Would I need any other components? Am I about to set the house on fire? It's been about 25 years since I made a living in electronics, so I'm a little rusty. Any help you guys could offer on this project would really be appreciated.