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Production and use of anticoronovirus lamp

An ultraviolet bactericidal lamp can be used for disinfection of rooms as one of the measures against coronovirus.

“The effect of disinfection is based on the direct destructive effect of ultraviolet rays in the spectrum with a wavelength of 200-300 nm and a maximum bactericidal effect of 260 nm ... ultraviolet rays can affect not only ordinary bacteria, but also spore organisms and viruses” - Chemistry Handbook [1] .

Detailed information on the use of ultraviolet radiation for disinfection can be found in [2].

Professional bactericidal plants are not cheap and the lamps intended for them cannot be screwed into an ordinary cartridge. This article will discuss the manufacture and use of a low-cost bactericidal lamp with a standard E27 or E14 lamp bulb powered by a 220V network based on a UV lamp with a 2G7 or G11 base and a second-hand electronic ballast of an energy-saving lamp.

Working lamp

Precautions when using a UV lamp.

  1. Exposure to ultraviolet radiation on the skin leads to burns of varying degrees, can cause skin cancer. Eye irradiation causes a burn of the cornea. Short-wave ultraviolet (100-280 nm) can penetrate to the retina. Room processing should be carried out only without people!
  2. When operating UV lamps, ozone is formed, which is highly toxic. After processing, the room must be ventilated. This does not apply to UV lamps made of UV glass that do not generate ozone because the glass absorbs the spectrum of radiation that creates ozone molecules.
  3. Many polymers used in consumer goods are degraded by UV light. It is not recommended for a long time to leave polymer products near operating UV lamps.

Depending on the power ratio of the UV lamp and electronic ballast, 3 options are possible:

  1. If the power of the lamp and ballast are the same, the task is simple: connect the lamp to the ballast and attach it to the housing.
  2. If the lamp power is greater than the ballast power, if you are lucky, it will work, but not at full power, but in accordance with the ballast power. Ballast limits the output current, so connecting excess power lamps will not disable it.
  3. If the lamp power is less - intervention is required in the design of the ballast in order to reduce power. This is the next section.

The device and operation of electronic ballasts.


A lot of articles have been written on this subject. Consider the first scheme from the article "Schemes, device and operation of energy-saving lamps" [3].

image
Figure 1: electronic ballast circuit diagram.

Of all the elements of the circuit, we are interested in:

  1. Lamp. The cathodes LMP1, LMP2 are indicated in the diagram. We will connect a UV lamp here.
  2. 3. , C3 600. , C3 . , , . .
  3. RT1 , PTC. . : , , , PTC , .
  4. F1 fuse required for fire safety.
  5. Output choke L1. Limits the current through the lamp.
  6. Feedback Transformer TR1. It is wound on a ferrite ring and is saturated. The generation frequency depends on its parameters, and on it the inductance of the inductor and the current through the lamp.

The voltage on the lamp depends on its characteristics and remains almost constant in the operating mode, so to change the power you need to change the current.

The document "Electronic Lamp Ballast Design" [4] provides a methodology for calculating electronic ballasts during development from scratch. When remaking finished electronic ballasts, the formulas come in handy:

  1. Formula (1) on p. 3 - dependence of inductive resistance on frequency.
  2. Formula (3) on p. 3, and unnumbered just below, linking the inductance of the inductor and the current through the lamp.
  3. (16) .8, .
  4. (18) .10, . .

    , . , . — .
  5. (6) .7 — , .
  6. , . , , : . , . , , . , , .

( )


  1. . U / , P1 . I1 = P1 / U1. / , , U1 U2 U1 = U2. - I2 = P2 / U2. I1/I2 .
  2. . Np. N = Np * (I1/I2 — 1) .
  3. . , . , UF4007 , / .
  4. ( ) .
  5. F1 ( ). I = 2P / U . / .
  6. . .

    1. -. 60-100 .
    2. , , .
    3. .
    4. 2 , 1 .


  1. . , .
  2. — , - .
  3. . . , , , .
  4. -. . -. . -, .
  5. . - / .

.


Lamp ultraviolet ESL-PL-9 / UVCB / 2G7 / CL (analogue DKBU-9) with a power of 9W. The voltage in the lamp is 60 ± 6V.

15W electronic ballast from Happy Light. The flask is defective.

I1 = 15/60 = 0.25 A
U1 = U2
I2 = 9/60 = 0.15 A
N = 4.67 rounded to 5 turns

The measured power value of 8.08 W differs to the lower side from the nominal 9 W, which is permissible since it slightly affects efficiency and does not reduce reliability.

Figure 2: Housing cover prior to completion
Figure 2: Housing cover before finalization

Figure 3: Feedback transformer with home-wound primary.
Figure 3: Feedback transformer with home winding primary winding.

Figure 4: Test connection of the UV lamp to the ballast.
Figure 4: Test connection of the UV lamp to the ballast.

Figure 5: Connecting the Oscilloscope Probes.
Figure 5: Connecting the Oscilloscope Probes.

Figure 6: Oscillograms of current and voltage.
Figure 6: Oscillograms of current and voltage.

Figure 7: Power waveform.
Figure 7: Power waveform.

Modified housing cover with installed UV lamp
Figure 8: Modified housing cover with installed UV lamp

image
Figure 9: Final connection of the UV lamp to the ballast.

image
Figure 10: Finished lamp.

Working lamp
Figure 11: Running lamp.

Sources
  2. 3.5.1904-04
  3. , ».
  4. AN1543/D Electronic Lamp Ballast Design

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