Sonic Mole Chaser Repairing
Today a really urgent call come down through the line of my phone, and somebody was jelling for help!
“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!
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.
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!
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.
– electro mechanic buzzer
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.
This article was prepared for you by Christian Robert Adzic from Novi Knezevac-Serbia.
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