Wart Zapper Circuit

I have had some warts on my feet, and I came across a circuit in Nuts & Volts Magazine to help remove them [1].  The basic concept of the circuit is that it uses high frequency current pulses through the wart to destroy it.  The article makes some mention of Crane Frequencies which are specific frequencies identified by Dr. John Crane in the 1950s as effective in destroying certain microbes.  The frequencies for warts are 2.127 kHz and 21.27 kHz.

Circuit Description

The functionality of the circuit in [1] can be described as follows:

12V oscillator -> FET switch

The FET switch turns on and off at the desired frequency (21.27 kHz) grounding the active side of an electrode when it is on.  The dispersive side of the electrode is connected to a 24V source.  The 24V source is created from the 12V supply input with a simple voltage boost circuit.  Most of the circuit is based on a Philips HEF4060BP oscillator IC.

My Implementation

I implemented the design with a Fairchild CD4060BCN equivalent of the HEF4060BP.  The design in [1] sets the frequency of the oscillator using pin 9, 10, and 11 of the IC with an RC circuit with C1 = 100 pF and R1 = 5 k Ohms.  Pin 11 is connected to the RC oscillator through R2 = 100 k Ohms.  The article mentions that the frequency should be adjustable by varying R1 so I made that a potentiometer.   The circuit from my implementation is shown in the following figure.




As it turned out, the circuit did not work with R2 = 100 k Ohms as specified in the article because this resistance was too large.  A resistance value of 22 k Ohms was found to work better through experimentation and consultation of the Fairchild datasheet.  Once I got everything working on the input side of the 4060, the voltage at DE was measured to be a fairly flat waveform at a level of 22.45 V (a little less than the 24 V mentioned in the article).  For Q1, the article used an IRF823 but stated that an IRF510 should be fine.  I used an IRF510 originally.  I found that with the original circuit applied to my wart, I did not get a very large peak to peak AC voltage across the wart.  The Q1 was able to drive the AE point pretty close to ground when it was on, but when Q1 was off, there was not enough drive current in the high direction to drive AE back to 24V.  The high drive was provided simply through the pull up resistor formed by my wart which is a pretty large resistance.  This was not enough to charge the capacitance of Q1 and my skin within the half period time of 21.27 kHz.  I did some experimentation with fixed resistors connected between AE and DE, and I also switched out Q1 for a lower capacitance FET (MPF102) and the results are listed as follows.

	Tested with Q1 = IRF510			Tested with Q1 = MPF102
Load	Vae min	Vae max	Vde - Vae peak to peak V	Vae min	Vae max	Vde - Vae peak to peak V
100 k Ohms	1.875 V	11.25 V	9.375 V	2.5 V	18.125 V	15.625 V
my wart with lotion	-225 mV	75 mV	300 mV	187.5 mV	1.5625 V	1.375 V
Rp=50 k Ohm and my wart with lotion	5 V	10 V	5 V	5 V	13.125 V	8.125 V
50 k Ohm	4.375 V	18.75 V	14.375 V	3.75 V	19.375 V	15.625 V

With a load of 100 k Ohms the original circuit with the IRF510 only delivers 9.375 V peak to peak to the load.  The article mentions that it is difficult to get skin resistance much below this level.  My wart's resistance must have been much larger because I only got about 300 mV peak to peak across it with the original circuit.  If the original circuit had any chance of working it was strictly through electrolysis effects from applying approximately 20 V DC across it.

With a modification to the circuit of adding Rp at 50 k Ohms and changing Q1 to an MPF102, I was able to get a peak to peak voltage delivered to the wart of 8.125 V.  Nothing ever happened to the wart though.  I followed the directions in the article and never even felt anything with the electrodes applied.  With the large resistance of my skin, I think the amount of power this circuit delivers is not sufficient to do much of anything.  I even tried cranking up the battery voltage to 18 V and still got no results.

The author refers to spectacular results in destroying warts with this circuit.  I did not see them with my warts.  I would be very interested to hear of anyone else's experience with this type of circuit.  The key is fighting through any initial problems with the 4060 IC, since it seems like characteristics of this chip vary from manufacturer to manufacturer.

[1] Scarborough, Thomas. February 2005. "Wart Remover." Nuts & Volts Vol. 26 No. 2 pp 30-34.