Pest repeller

Potato Pudding

Joined Jun 11, 2010
Can i use 555 as an oscillator instead of CA3130?
It might not have worked because that OP AMP is able to oscillate at a very high frequency with the 4017 dividing it, but I don't think it is too high for a 555 to reproduce in this circuit. I am not certain why they would use such a system.

Since you already have one 555 for the frequency x2 you might as well use a 556 dual timer and that would mean one less IC.
In fact if you use a ramp or triangle control voltage to VCO the signal feeder 555 you should be able to eliminate the counter and I think it would give you a better result.

Do you need help working out what components you need to get the frequency you would expect?

Potato Pudding

Joined Jun 11, 2010
Anybody else with LTSpice want to try and make this useful?

I am thinking that the transistor bridges could be replaced with Op Amps but I am not certain what the total advantages would be besides reducing components to a 556 dual timer and a dual or quad opamp. For Op Amps I would divide the supply into two 4.5Volts with center ground and connect the 555 grounds to the -4.5Volts unless anyone can tell me what problems that might cause.

I wanted a circuit that would drive specific noise frequency into a ceramic speaker.

I lowered the frequency range to 28kHz so that it should work on some other creatures. I need to research hearing response but I am hoping to affect mice, rats, racoons, foxes, coyotes, cats, and dogs. Some insects will avoid the higher frequency.

Two things I am still wanting to do that are at opposite purposes.

Lower power usage. When I probe the current from the 9V supply and ctrl-left click, the simulated trace it says about 63 mAmps RMS. From 9 Volts that puts this just over half a watt.

Increase the power going to the speaker by putting it in a full bridge. I would need another 2 transistor bridge driven in opposite phase connected so that their output is where the speaker is now connected to ground. This could also be used to connect a second speaker instead since the high impedance speakers probably limit the power anyways. Anybody who knows what I talking about and has a good answer or better question please offer it up.

And if anyone can make it look prettier that would also be helpful. It is still a mess of ideas trying to work more than a decent schematic.



Joined Jun 8, 2007
In the LTspice circuit, the piezo driver can be simplified pretty much. I like the transistor use in that circuit and the current source. I have made a triangle generator like that one once, but using 2N3904 and 2N3906, I was able to use high value base resistors to drive the transistors with current limited by just beta. If its just a personal project I like to take shortcuts like that latter one.


Joined Mar 24, 2008
One of the points of this schematic is it scans between several frequencies, around 5 or so, in an attempt to hit one that bugs the pest in question. Personally I think the design is pretty lame, the wave form driving the speaker (piezo) unsymmetrical, and the oscillator driving the 4017 overcomplicated (a 555 would work much better).

Thread Starter


Joined Aug 4, 2010
Thanks for the info. I will use 555 (replace CA3130) and 556 (one less IC). Anybody who could suggest a better circuit would be much appreciated.

Potato Pudding

Joined Jun 11, 2010
I don't think it is finished with more power in the output and reduction of the total watts being the main goals, and it is laid out just as something thrown together = a mess, but this should work. Adapting the two 555 shown to be one 556 is another change needed. That should be fairly trivial outside of the LTSPICE, but inside the program it would involve finding or creating a 556 model. That is why I used two of 555.

You would be better off to use LTspice and look at the simulation file I posted earlier.