Fig. 1: Timer circuit for mosquito destroyer In mosquito repellents that are heated electrically, a mat or liquid is heated by an electric vaporizer, which then causes the mat or liquid to release non-degrading compounds into the air. These chemicals keep insects away from enclosed areas. The following is a circuit for a Mosquito Destroyer that suspends normal machine function for a period of fifteen minutes. This does not compromise the device's ability to ward against mosquito bites in any way. Because the circuit in question (shown by Figure 1) does not employ any transformer-based power supply, it is sufficiently small to be housed within the switchboard. It is powered by 230V AC mains, which are passed through a voltage-limiting resistor known as R6 (22-kilo-ohm). In order to produce 12V DC, the low-voltage alternating current (AC) is first rectified by diodes D1 and D2, then filtered by capacitor C3, and finally regulated by zener diode ZD1. Utilizing a 14-state binary counter, IC HEF 4060 is what makes the timer action possible (IC1). The oscillations of the IC are controlled by capacitors C2, R2, and R3, and the blinking of LED1 coupled to the Q3 output (pin 7) of IC1 serves as an indicator of these oscillations. When the switch S1 is used to power on the circuit, the

integrated circuit IC1 is reset by the capacitor C1 and the resistor R1, and it then begins oscillating. After 15 minutes, the output of its Q11 swings high (pin 1), which causes the triac BT136 (triac1) to be triggered through the resistor R5. When the triac starts conducting electricity, the neutral line travels through the M2 terminal of the device to the plug socket. After being powered on for 15 minutes, the vaporizer that is attached to the power outlet will then turn itself off. Until the power switch S1 is switched off, this cycle will continue to repeat itself. As a result, the circuit contributes to a reduction in the amount of chemical vapours in the air that is breathed in. Because the vaporizer is only operational for fifty percent of the time, its power consumption is cut in half, effectively doubling the number of days it may be used. Construct the circuit using a PCB designed for general use, taking care to leave sufficient space between each component. For the exposed leads of components, particularly triacs and diodes, sleeving is an essential precaution to take. In order to complete the circuit, enclose it in the switch box, and connect the plug socket to it in the manner indicated on the circuit diagram. Caution, the author's prototype, can be seen in Figure 2. Because the circuit contains 230V AC, checking and repairing it requires the utmost caution in order to prevent potentially fatal shocks. You should only assemble it if you have the necessary training and experience to work with high voltages.