Latest zapper plans
I know this is going to astonish some people, but I have an opinion.... ;)
The Zapperplans circuit is very simple, but I don't think it is the best. I have some issues with the CD4069UB chip. The U stands for "unbuffered". This is the original CMOS chip design, virtually unchanged since the 70's. The outputs are not as "strong" (can't source as much current) as later designs, or any of the 555 parts. Also, the outputs and inputs have almost no anti-static protection. Not a problem in the humid days of Summer, but a potential one in the dry air of Winter. This potential problem can be greatly reduced by adding one diode. Let me know if you want the details.
Also, the Zapperplans circuit produces a perfectly symmetrical square wave. The 555-based circuits have a slight asymmetry, which increases the number of harmonics in the output signal.
So in your case, I would go with one of the 555 based designs. The three most common Zapper frequencies are 30,000Hz, 2,500Hz, and 15Hz. Others on this forum have much more to say about the relative effectiveness of these three signals, but all 3 versions are equally simple to build and low cost. The original Clark circuit with the NE555 (all bipolar transistors inside) is the standard against which all others are judged. Other than the fact that about 1/3 of the battery power goes into lighting the light, it is fine. The chip also dates back to the 70's, but is built like a tank to withstand the ultra-harsh automotive electronics environment. Changing the chip to the newer TLC555 (CMOS guts, but very heavily static protected) will probably double the battery life.
ak