This article details how to build a simple Buzz Coil Tester and is part of the Simple Buzz Coil series.

Before beginning it is very important that you note that the output (secondary) side of a Buzz Coil is extremely high voltage and is very dangerous. That voltage is going to be exposed on "open to fingers" terminals in this tester. Handle it the way you would handle a live spark plug!

The items you need to build this tester are:

  1. Plywood rectangle about 300mm x 400mm (approx 12" x 16")
  2. 12 VDC Volt Meter (at least 12V)
  3. Zero centre 3 Amp Ammeter (at least 3A)
  4. 3 Amp fuse and fuse holder
  5. 6VDC or 12VDC Sealed Gel Battery or Dry Cell
  6. 12 AWG Automotive wire
  7. 10 AWG Copper Spark Wire (not silicone)
  8. A set of spark gap terminals (can you spell "nails")
  9. Heavy Duty Alligator clips for terminating the wires at the buzz coil ends
  10. 12VDC 10Amp Toggle Switch - do not use a household fitting!
  11. You might consider adding a DC Earth Leakage Detector
Wire up the tester as per the above diagram - it should be across the supply wires from the battery rather than in series with the positive wire as shown above. Note that I have not built to this particular design the tester I made consisted of wire scraps and some nails, I was only interested to see if the unit sparked at all. This tester will allow you to test and adjust the Buzz Coil. Under no circumstances should this tester be mains wired, run it from a battery only. Thanks to This email address is being protected from spambots. You need JavaScript enabled to view it. for pointing out that the voltmeter was wrong in the original circuit.

spark The spark gap should be set at about 7mm (1/4"). This gap is of course much bigger than the gap in a spark plug as it is in the open air where the resistance to the arc leaping from terminal to terminal is much less than if it were in a compressed combustion mixture within a closed combustion chamber. Thanks to Roy Rice for the picture.

To test a buzz coil, wire it into the tester as shown in the diagram in the following order:

  1. Spark Connection
  2. Negative Connection
  3. Positive Connection
The order of Negative and Positive does not really matter, but the Spark wire is important - think about just how much you would enjoy holding the live end of the spark wire when the buzz coil is energised and you will understand!

Now that you have finished your tester, you can use it to test and adjust your coil.

As an added fun thing to do, you could get some steel wire (such as piano wire, or a guitar string) and make two vertical feelers at the spark gap which start about 7mm (1/4") away from each other then bend away. You've just made one of those interesting spark gap machines you often see in old horror and science fiction movies! Note that not all coils will be strong enough to make one of these work.

A further note is that this unit is a very effective spark gap transmitter and will disrupt television, radio and other such devices which are close to the unit.

This email address is being protected from spambots. You need JavaScript enabled to view it.made a terrific version of the tester outlined above... I would prefer analogue meters for testing unless you can afford a true RMS digital meter with very fast sampling and min/max storage such as the higher end Fluke meters. Many digital meters do not check the input fast enough to detect small quick changes. Make sure you don't hook up a digital meter in line with the spark line or you can kiss it good bye! You can visit Roy's homepage`.
The photos in this article are © Copyright Roy Rice 2001 All Rights Reserved.