PackRatWorkshop BOBBLE GENERATOR Page
This is what I call a bobble generator. It is designed primarily for charging batteries.
It’s a very simple idea where you have a coil of wire with a loose magnet inside the coil. You pass another magnet near the coil and it causes the magnet in the coil to flip around at high speed generating at least one pulse of power from the coil and sometimes more. There is very little noticable drag from flipping the magnets in the coils. On a bike you don’t even notice what little drag there is. I have two of his coils using 4 wheel magnets on my recumbent tadpole trike’s rear wheel. The two coils operate two home-made rear taillights that have 9 leds in each light. They work very well and are really hard to ignore because they flash pretty wildly the way I have them wired.
As long my home-made generator rotor is turning at least 20-30 rpm it can cause the magnets in the generator coil to flip over fast enough to start to produce electricity. My versions seem to work the best about 60-100 rpm depending on the version. Going faster than about 200 rpm with one my test generators drops the ouput as the magnets no longer have time to flip over before the next magnet comes along. This doesn’t happen with the bike light and is solely a side effect of my generator because of the rotor magnets being fairly close together.
The 2 pictures below give you an idea of whats happening when the magnet goes by the coil setup. There is another really good diagram at the bike light website above. He also has a small movie you can watch that show one of his setups in action on a bike and you can see the magnet in the coil spinning around a few times every time the magnet passes it.
My original prototype had 200 ft of 30 gage wire per coil and the voltage output was 3 vdc with average 20 millamp pulses from each coil at about 100 rpm.
This was the first version that was spinable. My first tries were just to see what a single coil and magnet would put out and if I could use more than one hooked up in series or parallel. This one only used 4 coil setups on each side and 3 magnets on the rotor. It would light up 5 leds easily and actually keep them going for a few seconds after you stopped spinning the rotor due to the charge built up in the capacitor on each coil. I decided to go ahead and try building bigger versions after this as it worked well.
I was doing some adjusting to the rotor spacing on my larger version and noticed that one of the coil ends was coming off. While trying to fix it, I managed to finish popping it loose from the glue and the magnet fell out onto the rotor board. I removed the magnet to get it out of the way and started to place it on a metal strip that is on my desk so it would stay put. I expected it to try to snap quicky to the strip like they all had when I was building the coils but it just when “clink”… After getting one of the same type out that had not been used yet and comparing them, the used magnet has lost at least 1/2 and possibly as much as 2/3 of it’s field strengh. This is after only about 500-700 rotations of the armature in the generator in total since I have completed it. The end result? It seems that I got some poor quality magnets as I have been in contact with a number of people on the net and they all said this shouldn’t have happened.
This third version works a bit better than the last two. It is made with 24 coils, 12 per side and uses 6 magnets in the rotor. (magnets from a different supplier!) I went with 1200 turns of 30 gage on a 1 inch by 7/8 inch section of pvc pipe for each coil. Each coil contains a 3/4 inch by 5/8 inch disk super magnet. The coil boards are set up so each rotor magnet passes a coil on both boards alternately in a left-right fashion. All coils are connected in parallel to a common set of output terminals. So far 60-70 rpm seems to give the best output.
Measurments taken at 60 rpm
Voltage and current readings with a small dc motor was approx. 6 vdc at 350 milliamps.
I didn’t bother with pictures this time as it looks just like version 2 above.
I went in a slightly different direction this time. The coils have 1500 turns of 30 gage wire on handmade plastic forms just slightly bigger that the magnets themselves.
This version uses 1/2″ sphere magnets in an attempt to get the field closer to the coils. The magnets are lubricated with graphite powder which reduces the friction. This setup is a lot quieter than the others also because the ball magnets just spin around in place instead of bouncing inside the coil forms. It also has a lot less vibration due to the same reason.
I used 8 coils and 8 magnets on the rotor. The rotor magnets are 3/8″ squares. All the coils are wired with individual full wave rectifiers like the other versions and this time they have 150uF/50 volt caps. (I had a bag full of these in my junk box) All the coils are wired parallel to a common output.
Open voltage across terminals is 10 volts at 60 rpm.