09-08-2012, 09:50 AM
TIMER FOR MOSQUITO DESTROYER
timer for mosquito destroyer.docx (Size: 1.43 MB / Downloads: 56)
INTRODUCTION
In electric heating mosquito repel-lents, an electric vaporizer heats up a mat or liquid to release non-degrading chemical into the air and keep the mosquitoes away from the closed surroundings.
Here’s a circuit that introduces a time gap in the operation of the vaporizer to reduce the amount of toxic chemical vapours in the inhaling air and thus their ill effects. The circuit turns the device on and off at a interval of 15 minutes without reducing the repellent action on mosquitoes. The circuit (Fig. 1) doesn’t use any transformer- based power supply and is therefore compact enough to enclose inside the switchboard. It is directly powered by 230V AC mains through voltage-limiting resistor R6 (22-kilo-ohm). The timer action is achieved using 14-state binary counter IC HEF 4060 (ICI). Oscillations of the IC are controlled by C2,R2 and R3 and inkcal by the flashing of LED1 connected to Q3 output (pin 7) of ICI.
When the circuit is powered-on using switch S1, ICI reset through capacitor C1 and resistor R1 and starts oscillating. After 15 minutes, its Q11 output (pin) goes high to trigger triac BT136 (triac1) through resistor R5. Once the triac fires, the neutral line reaches the plug socket through M2 terminal of the triac. The vaporizer connected to the plug socket turns on for 15 minutes and then turns off. This cycle repeats until power switch S1 is turned off. Thus the circuit helps to reduce the amount of chemical vapours in the inhaling air. As the vaporizer works only half of the time, it reduces the power consumption to half, doubling the days of usage.
WORKING
Here’s a circuit that introduces a time gap in the operation of the vaporizer to reduce the amount of toxic chemical vapours in the inhaling air and thus their ill effects. The circuit turns the device on and off at a interval of 15 minutes without reducing the repellent action on mosquitoes. The circuit (Fig. 1) doesn’t use any transformer- based power supply and is therefore compact enough to enclose inside the switchboard. It is directly powered by 230V AC mains through voltage-limiting resistor R6 (22-kilo-ohm). The timer action is achieved using 14-state binary counter IC HEF 4060 (ICI). Oscillations of the IC are controlled by C2,R2 and R3 and inkcal by the flashing of LED1 connected to Q3 output (pin 7) of ICI.
When the circuit is powered-on using switch S1, ICI reset through capacitor C1 and resistor R1 and starts oscillating. After 15 minutes, its Q11 output (pin) goes high to trigger triac BT136 (triac1) through resistor R5. Once the triac fires, the neutral line reaches the plug socket through M2 terminal of the triac. The vaporizer connected to the plug socket turns on for 15 minutes and then turns off. This cycle repeats until power switch S1 is turned off. Thus the circuit helps to reduce the amount of chemical vapours in the inhaling air. As the vaporizer works only half of the time, it reduces the power consumption to half, doubling the days of usage.
Assemble the circuit on a general-purpose PCB ensuring adequate spacing between the components. Sleeving is necessary for the exposed leads of components, especially triacs and diodes. Enclose the circuit in the switch box and connect the plug socket as shown in the circuit diagram. Fig2 shows the author’s prototype.
COMPONENT DESCRIPTION
Capacitor
A capacitor (originally known as condenser) is a passive two-terminal electrical component used to store energy in an electric field. The forms of practical capacitors vary widely, but all contain at least two electrical conductors separated by a dielectric (insulator); for example, one common construction consists of metal foils separated by a thin layer of insulating film. Capacitors are widely used as parts of electrical circuits in many common electrical devices.
Resistor
A resistor is a passive two-terminal electrical component that implements electrical resistance as a circuit element. The current through a resistor is in direct proportion to the voltage across the resistor's terminals. Thus, the ratio of the voltage applied across a resistor's terminals to the intensity of current through the circuit is called resistance. This relation is represented by Ohm's law.
Transistor
A transistor is a semiconductor device used to amplify and switch electronic signals and power. It is composed of a semiconductor material with at least three terminals for connection to an external circuit. A voltage or current applied to one pair of the transistor's terminals changes the current flowing through another pair of terminals. Because the controlled (output) power can be higher than the controlling (input) power, a transistor can amplify a signal. Today, some transistors are packaged individually, but many more are found embedded in integrated circuits.
Light-emitting diode
A light-emitting diode (LED) is a semiconductor light source.[3] LEDs are used as indicator lamps in many devices and are increasingly used for other lighting. Introduced as a practical electronic component in 1962,[4] early LEDs emitted low-intensity red light, but modern versions are available across the visible, ultraviolet, and infrared wavelengths, with very high brightness.
PCB DESIGNING:
A printed circuit board, or PCB, is used to mechanically support and electrically connect electronic components using conductive pathways, tracks or signal traces etched from copper sheets laminated onto a non-conductive substrate. It is also referred to as printed wiring board (PWB) or etched wiring board.
A PCB populated with electronic components is a printed circuit assembly (PCA), also known as a printed circuit board assembly or PCB Assembly (PCBA). Printed circuit boards are used in virtually all but the simplest commercially produced electronic devices.
ETCHING:
It is done with ferric chloride, ammonium persulfate, or sometimes hydrochloric acid. For PTH (plated-through holes), additional steps of electroless deposition are done after the holes are drilled, then copper is electroplated to build up the thickness, the boards are screened, and plated with tin/lead. The tin/lead becomes the resist leaving the bare copper to be etched away.
DRILLING:
Holes through a PCB are typically drilled with small-diameter drill bits made of solid coated tungsten carbide. Coated tungsten carbide is recommended since many board materials are very abrasive and drilling must be high RPM and high feed to be cost effective. Drill bits must also remain sharp so as not to mar or tear the traces. Drilling with high-speed-steel is simply not feasible since the drill bits will dull quickly and thus tear the copper and ruin the boards. The drilling is performed by automated drilling machines with placement controlled by a drill tape or drill file. These computer-generated files are also called numerically controlled drill (NCD) files or "Excellon files". The drill file describes the location and size of each drilled hole. These holes are often filled with annular rings (hollow rivets) to create vias. Vias allow the electrical and thermal connection of conductors on opposite sides of the PCB.