Here is the simple and low cost mosquito repellent circuit design. The circuit serves to keep the mosquitoes out of the room or the location where the device is installed. According to certain publications, the frequency emitted by the male mosquitoes is said to be around 20??”25 kHz, and so within the realm of ultrasound. But according to others, it is in the region of 5??”7 kHz instead; frequencies that a human ear, even an elderly one, can still hear very well. Rather than spending lots of money buying such a device, which moreover generally have a fixed frequency, we’re suggesting building one yourself , especially since the circuit proposed is very simple and cheap to build.
Mosquito Repellent Works
The low cost mosquito repellent circuit uses just a single IC, a CMOS type 4047. This very multi-purpose IC can be wired in very many operating modes, including that of the multivibrator or astable used here. The operating frequency is set by the external components C1, R1, and P1. The latter makes it possible to slightly adjust the frequency, given the uncertainty that exists over the most efective value. To best reproduce the high frequencies produced by the generator, the output transducer used is a simple tweeter, but it must be a piezo one. Such a tweeter behaves in fact much like a capacitor, and so doesn’t overload the CMOS IC outputs that are incapable of supplying a substantial current.
To obtain an output signal of sufficient amplitude while being powered from a single 9 V battery. The tweeter is connected between the 4047’s Q and Q outputs. With this condition, it possible to apply complementary (antiphase) signals to the tweeter so it ‘sees’ an alternating voltage of double the supply voltage. In purely theoretical terms, this quadruples the output power available. In practice, it’s better to regard it as tripling it, but the beneft achieved by doing it this way is nonetheless very real. All that remains is for you to place the project in the middle of the patio table or beside your lounger in order to get a taste of the calm of a summer’s evening without mosquitoes bothering you acoustically or worse, biting. At any rate, that’s what we wish for you.
Source: eeweb
