The heart of this detector is one of Grampa's old double-edged razor blades. Lightning is essentially a discharge of static electricity. Our little device measures this static electricity as it flows from the ground and up to our razor blade where it is dissipated into the atmosphere.
As the name implies this simple unit also "repels" lightning. What you have here is the same principal of technology used by commercial broadcasters and cell phone companies to protect their tower sites. Their costly static discharge arrays serve to remove static electricity from the vicinity of a building or antenna. Grampa's razor blade does the same.
Okay, so lets build the darn thing. Here is the good news, its FAST, SIMPLE, and CHEAP to build.
First we need to ionize the air around the edges of the razor blade. To achieve this we must make our razor blade RADIOACTIVE. You can achieve this by leaving the blade in its wrapper and placing it in your shirt pocket, next go to the hospital and ask for a dozen chest x-rays..............just kidding!
Our blade only needs to the tiniest bit of radiation, and you will find this radiation source in the camping and sporting goods section of your local Walmart, K-mart, or other super store.
Purchase a mantle for a gas camping lantern. These are small mesh bags that are ignited to provide the light source. They are very in-expensive.
the Thorium increases the flow and response of electrons along the edge of the razor blade. PLEASE NOTE: Coleman mantels no longer contain Thorium so you most purchase ALLADIN or another brand of mantel to use.
With a pair of needle nose pliers, hold one of the mantels over a clean disposable surface and set it on fire. The mantel will quickly burn itself out and turn to ash. Crush the mantel into a powdery ash. Next, squeeze a glob of quick setting epoxy glue (I bought mine at the 99 cent store for a buck) into the ash and mix into a paste.
Now coat the edges of your razor blade with a layer of this paste approx, 1/16 inch thick, let the expoxy harden (5-10 minutes).
The "brains" of your detector is a digital multi-meter. On my detector I have a dedicated meter which I purchased from HARBOR FREIGHT for $2.98
Attach a wire to the razor blade, you can use an alligator clip or other clamp ( I "spot welded" mine by momentarily shorting across an old car battery, if you choose to do this be extremely careful as anything longer than a split second of contact can cause the battery to explode!)
Cut a 10-12 inch piece of dowel rod or similar material and slit one end, insert the razor blade and attach the rod to an eave of your house or other high location. Run the wire down to your multi-meter and connect it to the positive (+) lead.
Take another piece of wire and connect it to the negative (-) lead of your meter and run this outside the house. Locate the ground rod for your homes power meter or telephone utility box. Hook this wire to the ground rod using ahose clamp or split bolt connector. If you can not locate one of these ground rods, hammer a 5 ft piece of pipe or other metal into the ground (if you do this near a plant that is irrigated by a drip sprinkler the moist soil will improve your ground). The better this ground is the better your readings will be.
Set your meter for milli-amps. Following a lightning strike the electrical potential between the sky and the earth will become equal and your meter reading will drop to zero. The reading will then begin to increase until the next strike.
Observe the current and time between discharges, you will soon be able to predict the lightning flashes and their distance from your location.
Have fun with Grampa's old razor-blades....73 John-N7UR