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Sonic Mole Chaser Repairing

By on January 30, 2019
Sonic Mole Chaser Repairing












Today a really urgent call come down through the line of my phone, and somebody was jelling for help!

Sonic Mole Chaser Repairing

“Huston! Huston! We have a problem!” after a listened what is going wrong I realized a missile was failed to launch which should protect the planet Earth from mole attack! Huh! That’s a crazy situation and I have to solve the problem. So, Let’s save the planet from mole attack!

Sonic Mole Chaser Repairing

sonic mole chaser fix

So, here we deal with a really tuff weapon, which failed to launch and moles attacked began. Unfortunately the owner lost the battle over his lawn. Let’s investigate this toy. Yes, I say it is a toy and not a really usable tool for mole repelling. The tool was dead, no signs of life in there. The main concept of this toy is a nice electronic circuit setup with a 555 timer in monostable mode.

The 555 timer fire a signal to the electro mechanic buzzer for 1s long and then it will wait for 40sec delay and the buzzer will fire again. I checked first if the batteries are good and they are in excellent condition. Then I checked for some shortening on the input and output, but I didn’t realize anything wrong.

I assume that several resistors and filter cap’s are in good conditions, I checked the output signal on the 555 timer on pin 3. The signal was continuously HIGH and that means the PNP transistor on the pin 3 which serves like a driver for the buzzer is non-stop closed.

sonic mole chaser fix pcb

sonic mole chaser fix pcb repair

 This is the pcb.

Maybe somebody will make this circuit to “defense” his own lawn. The circuit is really simple. After I realized the output is bad on the 555 timer I decide to change the timer IC and connected my scope again to check what’s going on now. When the new IC was fitted the toy was working again!

circuit waveform

The ON time is around 1sec and the off time is around 40sec. This process is repeating in an infinity loop or better to say, until the batteries die.

I realized quickly does the boozer is also bad, I had to change it and the unit was working like before.

Changed parts:

– NE555

– electro mechanic buzzer

ne555 ic

Why I treat this unit as a toy would maybe ask somebody, the reason is because this tool is repeating the whole buzzing process in a same time constant. That means, in every 40sec the buzzer will go ON for 1sec.

When you use this mole repellent, in the first period of time maybe several days, maybe the moles will take off but after a short period of time the moles will recognize this noise as a regular noise without any danger to them. That means, they will adapt them self to the new noise in his area and they will start to ignore the noise made by the buzzer.


Conclusion, this tool is not worth the money (around 50EU in my region) from my angel of perspective, even not the money for repairing it. However, the owner decided to repair the unit and I done it with success.

I hope you enjoy this tutorial and will save lot of repair time.

Christian Robert Adzic

This article was prepared for you by Christian Robert Adzic from Novi Knezevac-Serbia.

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  1. Parasuraman S

    January 30, 2019 at 10:32 pm

    Vow! That is something new! The narration is like a war movie and I liked it very much, as I have a lot of 'kid' hanging around within me! Good job!

  2. Albert van Bemmelen

    January 30, 2019 at 10:42 pm

    Thanks for the info on the Mole repeller circuit Christian. The 7555 is the CMOS low current version of the standard NE555 which is significantly improved. I probably won't see moles in my apartment/flat at the second floor so I won't need it. But a mouse and insects like snails I had seen a lot because I have a lot of strawberry plants on my Balcony. They all are drawn to the plants and one small pear tree. My little way in giving something back to nature in case I lose a few strawberries. And to help the birds and the bees.

  3. Fred C

    January 31, 2019 at 6:05 am

    I think you are probably right about these kind of repelling devices, but I wonder if in fact this was helping as the owner seemed to think it was and he may be the best determiner of that. And I don't know if the moles may sense this is a regular tone so they may ignore it, but if so it would be better to have the buzzer go off more randomly and for a random buzz period. Thanks for the help and stay safe over there. Fred from the US.

  4. Robert Calk Jr.

    February 5, 2019 at 10:42 am

    Thanks Chris. That was funny! It is spelled, Houston. You could change the timing periodically to scare the moles.

    • Christian Adzic

      February 12, 2019 at 4:56 am

      Thank you for supporting my article and thank you very much for pointing to my grammatically problem, I really appreciate that kind of help, because english is my fourth language I speak. With help of people like you, I can make better my writing skill too.
      Thank you.
      My best regards.

  5. Doug

    May 8, 2023 at 11:58 am

    Question on this: is it possible to change the hertz frequency to something lower by making a change on the circuit board?

  6. Chir

    June 16, 2023 at 6:38 pm

    Thank you for supporting my article.
    Yes, it is possible.
    Play with the cap and resistor and you will deal with the output frequency of the time.
    Search the net for some timer calculator for ne555 and you will get what you need.
    My best regards.


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