Intro: Mini Van De Graaf... M & M Style!
I'd been thinking about making a VDG generator ever since I read this Instructable and this one too , and I'd read up on how they work: http://www.rmcybernetics.com/science/high_voltage/contact_elec.htm, but I was at a loss as to what to stick on top of the thing... until I came across this ~3" metal M&M box, just crying out to be charged up!
(It's only entered in the tool contest because of the Makita-as-motor, which is at best a stretch, I'm fully aware)
Step 1: Materials
In keeping with the purest standards of junk craft, I refused to purchase anything for this project. But over time I was able to extract the following from my various hoards of trash:
Here's a great reference:
(The diagram I've posted is from that page)
- Metal M & M
- Copper wire, solid
- copper wire, stranded
- Big black rubber band: 1/2" wide, ~6" extended
- 1" diameter PVC pipe (cut to a bit over 7")
- Old PC power cable (for ground)
- 1/4" dia. bolt; 2 1-4" long (toilet tank mounting hardware, if I recall correctly), & nut
- plastic "beads" from a jump rope (my daughter's jump rope had half a dozen of these left over after I shortened her rope)
- Wire hanger (welding rod, etc would work)
- glass beads
- Gorilla Glue
- Cordless Drill (I tried using some random motors, but none of them had enough torque to spin my low-tech roller!)
NOTE: none of these measurements is exact, nor do they need to be; for instance I cut the PVC pipe to fit the rubber band I had.
- wire strippers, cutters
- soldering iron
Step 2: Sphere, Pipe
I sanded the lovely paint job off of my M & M, punched a hole in the bottom and chewed it into a bigger hole (1", to fit the PVC pipe) using wire cutters. Definitely not a clean cut, but I hid my shoddy workmanship later under a halo of Gorilla Glue. Don't tell. Some nice tin snips would have been swell.
I cut a 7" length of PVC, just eyeballing the length compared to my rubber band. Longer or shorter, I didn't notice any info out there about whether the length of the belt (and therefore the housing) matters much.
I drilled a 1/4" hole through the pipe for the "bottom" roller, and a small hole near the top for the upper roller's "axle," made from wire hanger.
To make the top roller removable, I also drilled a bigger hole above the "wire" hole (on one side), large enough to admit the diameter of the finished roller (see step 3). I then cut a slot between the two holes, so the roller goes in at an angle, then snaps into place.
Step 3: Rollers
The "jump rope" bead spins freely on the bolt. I had to shorten the bead a bit, but it worked without much persuasion. I just threaded the bolt through the PVC, bead and belt, then through the nut (easy to remove for later experiments).
Apparently glass is a good material for the top roller (pretty high in the triboelectric series ) , and the first idea was a common cylindrical glass object: the fuse. But with the likelihood of breakage looming, I went instead with glass beads Gorilla-glued to a length of wire. I left an extra inch or so sticking out to attach to the motor.
To install the roller, I hook the rubber band (with a piece of wire bent into an "L" shape) and pull it up past the holes drilled n the PVC, insert the glass roller at an angle through the "big" hole, through the rubber band, and into the small hole on the opposite side. Then the roller snaps down into it's small hole, and into a horizontal position.
Step 4: Brushes
I made two identical "brushes" using insulated solid copper wire soldered to stranded copper (from an old extension cord), and made it purty with heat shrink tubing.
The top brush is soldered to the M&M, with it's copper fanned out and almost touching the top of the belt at the top roller.
The bottom brush is connected to ground (see step 5), and also barely touching the belt, at the bottom roller.
Step 5: Ground
I read that a connection to ground will supply a constant stream of electrons for "storage" in the sphere, and I figured the easiest way to ground such a creature would be to use a grounded plug.
I placed a screw into the ground (center) of a 3-prong PC power cord, and attached the bottom brush wire to it. I tested it with a volt meter to make sure it was a good connection and I hadn't accidentally shorted to the wrong prong (good name for a band!).
WARNING: don't go screwing screws into power plugs, it's ill-advised. But if you must, stick with the center hole, which leads to the round plug, which is ground, which won't do anything bad to you or your VDG. Unless lightning strikes, perhaps?
I also zip-tied the cord for strain relief.
Step 6: Fire It Up
After a few failed attempts at spinning the apparatus with small motors, I gave up and pulled out my trusty Makita, and tightened it to the wire roller.
With the VDG, you've got to keep the humidity low. Hose it with a blow dryer and you're better off.
So far I can get 1/4" sparks to jump to my finger. I can get rice crispies to crawl up a plastic cup. I can get packing peanuts to stick to the M&M. Definitely low power VDG tricks, lots of fun demos out there to try!
Step 7: Improvements
Other things to try:
I plan to make a few different "bottom" rollers from the jump rope beads, by sticking different materials to them: aluminum foil, for instance. I'll report back with what works best!
I didn't go to great lengths to clean the rubber band before I used it, so it could have oils or other contaminants on it that could affect it's ability to transport electrons.
I'll try other belt materials. Sounds like the good VDGs use fabrics: nylons, spandex?
I just got a small desktop grinder from Science & Surplus (believe it or not, using the gift certificate they gave me for the pumpkin carving contest!!). It has a flexible rotary-tool attachment that might work great to spin the rollers. Quieter than the drill.
Motors: I'll keep an eye out for a higher torque motor; I'm already plugging this contraption into the wall so I might as well use AC to drive a dedicated motor.
Let me know if you have any suggestions, I'm just using what's lying around in my house and guessing with the help of a few websites, I'm sure I've missed a lot.
Have fun if you make one, I dare you to stick your tongue on it!
No, I take that back.
Stick somebody else's tongue on it.
Thanks for looking!