The Prize

A photodiary of a sucessful couple of hours.

A sucessful trip to Revolve

Ready to start work

Work in progress

First sight

The prize

The coil is actually freaky. The whipper-snipper does not have a distributor. Instead, it’s done magnetically (!!). See how the core of the transformer has a circular gap? There’s a lump of metal on the cooling fan on the shaft that closes and breaks the magnetic circuit as it goes past. Freaky.

Voltage

Well, I abandoned my voltage multiplier thingy and just went the other way. I bought a cheap little plasma ball. These guys emit kilovolts at the hot end at radio frequency.

To turn this into a static grass applicator, I added a pair of diodes and a capacitor, and a couple of 1MΩ resistors for safety.

Ignore the 1N4001 on the diodes – I went into Jaycar and said “give me the biggest diodes you have”. Dude asked “are they carrying a lot of current?”, and I was like “Naaah”. I wound up with a pair of these fat bastards. Like a 1N4001, but three or four times the diameter. Capacitor was the biggest one from the “high voltage” bin. Fat resistors, too, although probably not necessary. Again – not a lot of current.

Anyway. And it simply seems to work. My mate the modeller has been playing with it, finding out what combinations of things work best. His latest to me was:

I rewatched some terrain videos and tried a few changes, which gave the best effects so far.
Thicker PVA glue is better than watered down, as the bits spear in and don’t get mired sideways as easily.
A smaller mesh lets fewer bits through at once, avoiding the matted effect, and perhaps allowing more charge to accumulate per bit of grass. I used a finer mesh kitchen strainer, holding it with a silicon oven mitt to insulate it. Must wash it afterwards. 🙂
Lastly, tapping the grass in a dabbing motion with the mesh definitely lifts the grass up. This is easier with a mesh that protrudes downwards like the kitchen strainer.
I’d like to try some longer grass as I’m using 2mm, which is the shortest.

The results look like this:

So in the end, I needed to buy a manufactured thing. Which I had not wanted to do. But on the plus side, no-one else seems to have used a plasma ball, so I have done this a way that I had not found on the net.

You’d thing that circuit wouldn’t do anything at all, but I suspect the HF coming off the transformer is key. You definitely get a spark off the capacitor if you bypass the resistors. It might be better if one of the outputs off the diode went through something to phase-shift it, but that’s really a bit beyond me.

The resistors will limit the charge should the output be connected to something leaking at a comparable resistance, but that’s not what we are doing. Instead, the charge will be limited by the natural capacitance of whatever you clip the alligator clips onto. I have suggested that putting the work pieces on upturned glass jars might be the go. The unit works well enough that there’s no pressing need to remove the resistors, and I feel happier knowing they are there.

I found one interesting thing on the plasma ball board: an inverter chip. I bet that’s how they are generating the HF: just wire an odd number of inverters in a cycle. I hope that’s true, because it means they are essentially using a Minecraft redstone oscillator.

$20 for the little plasma ball, $10 worth of parts, not including the false starts and the stuff that is going into the parts bin.

So there you have it. We go from “Jeez, it would be tres cool to have one of those static thingies” to “Well, here you are then! Go nuts!”

Voltage

Goddammit. Gave me a hell of a fright, let me tell you.

Uh-oh

Blew the traces off

Nearly ready to admit defeat, but not quite.