A simple and low-cost mosquito repellent circuit design

This is a simple and low-cost mosquito repellent circuit design. The circuit is used to prevent mosquitoes from entering the room or the place where the device is installed. According to some publications, it is said that the frequency emitted by male mosquitoes is about 20"25kHz, which belongs to the ultrasonic range. But according to others, it is in the 5"7kHz range; a frequency that the human ear, even the elderly, can still hear very well. Instead of spending a lot of money on such a device, which usually has a fixed frequency, we recommend that you build one yourself, especially since the proposed circuit is very simple and cheap to build.

Mosquito repellent works

The low-cost mosquito repellent circuit uses only one IC, the CMOS type 4047. This very versatile IC can be connected to several operating modes, including the multivibrator used here or the astable circuit. The operating frequency is set by the external components C1, R1 and P1. The latter allows to adjust the frequency slightly, taking into account the uncertainty that exists in the most effective value. In order to best reproduce the high frequencies produced by the generator, the output transducer used is a simple tweeter, but it must be a piezoelectric speaker. This tweeter behaves practically like a capacitor and therefore does not overload the CMOSIC output, which is not able to supply much current.

Get an output signal of sufficient amplitude while being powered by a single 9V battery. The tweeter is connected between the Q and Q outputs of the 4047. In this case, a complementary (anti-phase) signal can be applied to the tweeter, causing it to "see" an AC voltage of double the supply voltage. In purely theoretical terms, this quadruples the available output power. In practice, it is better to think of it as tripling, but the benefits gained by doing so are very real. All that remains is for you to place the project in the middle of the patio table or next to the deckchair in order to experience the tranquility of a summer evening without mosquitoes disturbing you acoustically, or worse, biting. That is what we wish for you anyway.