Bug zapper
From Wikipedia, the free encyclopedia
A bug zapper is a device that attracts and kills insects that are attracted by light. A light source attracts insects to an electrical grid, where they are electrocuted by the a high-voltage. The name stems from the characteristic "zzzap" sound produced when an insect is electrocuted.
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[edit] History
According to the US Patent and Copyright Office, the first bug zapper was patented in 1934 by William F. Folmer and Harrison L. Chapin. They were issued patent no. 1,962,439.
[edit] How They Work
Bug zappers are usually housed in plastic or grounded metal mesh. A light source, mounted in the middle, often a fluorescent lamp (designed to emit insect-attractive ultraviolet light). The light is surrounded by a pair cages of carefully spaced and electrically insulated charged wire grids. A voltage multiplier circuit (comprising of diodes and capacitors) and/or transformer increases the voltage of a power source to at least to break down the dielectric formed (typically over 1,000 volts but lower voltages may be used) when an insect comes close enough to the the mesh pair. An electrical arc is formed when the dielectric breaks down traveling through the insects body. The insects body contains water which acts as a conductor. The insect is electrocuted and then dried. As the current passes through the insect the water evaporates and the body of the insect becomes an insulator to some extent. Its important to note that an insect doesn't have to touch both wires, for an arc will form in an air gap over 1000v. (As a rule of thumb an arch will form 1000v/mm starting at about 1mm). High Voltages also cause some localized high temperatures which can have a sterilizing effect.
Insect zapper may fail to work correctly in high humidity and if too many insects are attached to the electrical mesh. The humidity causes current to flow and thus the zapper can loose effectiveness. Each insect even if dry can still conduct electricity reducing the effectiveness of the bug zapper. Hence the need for periodic cleaning using a jet of air to remove insect stuck in the mesh.
Placement of the bug zapper is usually best in a high sheltered outdoor area, away from wind but in good view to attract the insects. Many insects bask in the light around the bug zapper, so sometime spraying the area with an aerosol also reduce the insect population. Insect zappers generally shouldn't be placed over cooking or eating areas as insect are attracted to the area and dead insects can fall into areas immediately below contaminating food areas. If an insect zapper is placed in an eating / food preperation are it should be placed in a clear area.
Insect zappers used in conjunction with yellow fluorescent lights can greatly reduce the annoyance to you by keeping insects attracted to one area while activities are carried out in another area.
Many bug zappers are also equipped with shallow trays that collect the remains of the electrocuted insects.
A novel variant is the manual bug zapper or electric fly swatter, which resembles a small tennis racquet strung with electrified wire. To use the device, one swats the insect, zapping it, and then collects and discards the insect.
[edit] Drawbacks
- Mosquitos - Although many people use bug zappers to control mosquito populations, the actual number of mosquitoes that are attracted to the devices is quite low if none at all(depending on the species and area), as mosquitoes are attracted to carbon dioxide, water vapour, and motion, rather than to UV light.
- Beneficial insects, or those that are harmless to humans are killed indiscriminately.
- The strong UV light attracts many insects indoors or to the patio that would not otherwise be present. Those who are not killed may bring pathogens dangerous to humans or animals.
- Improperly designed insects zappers can incinerate insects (due to excessive power), in some instances their bodies virtually explode, becoming an aerosol which may settle onto nearby food or be inhaled by humans. This could cause contamination, as viruses, fungi's and bacteria cab travel on particles.
- Bug zapper can attract other animals or pest feeding on the dead insects if not maintained.
Given the design, placement, and maintenance consideration Bug zappers are usually subject of health guidelines and or regulations for public and commercial premises. i.e. Hospitals, food processing plants.
