RU2503951C2 - Method to detect dust deposit on printed circuit boards of radio electronics equipment - Google Patents

Abstract

FIELD: measurement equipment.

SUBSTANCE: method to detect dust deposit with account of moisture level on printed circuit boards of radio electronics equipment consists in the fact that light pulses are periodically emitted by two light diodes with wave length λ₁=565 nm (to take into account the level of dust deposit) and two light diodes with wave length λ₂=930 nm (to take into account the level of moist dust deposit) and are received as reflected from three plates. At the same time the first plate has an artificially applied maximum level of dust deposit, the second one is in a tight body with artificially created maximum level of dust deposit with the limit threshold of moisture, and the third one is a reference plate, a photosensor. Besides, the photosensor first records the light pulses of two light diodes with wave length λ₁, then light pulses of two light diodes with wave length λ₂, arriving at the angle to the optical axis of radiation, comparing them by means of subtraction, as a result of which the higher level of dust deposit is detected, as well as availability of moist dust deposit.

EFFECT: provision of indication of higher level of dust deposit, disconnection of radio electronics equipment as the limit threshold of moist dust deposit is achieved.

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Description

The invention relates to methods for detecting dust deposition taking into account the level of humidity on printed circuit boards of electronic equipment, to devices for detecting dust deposition taking into account the level of humidity on printed circuit boards, in the event of which leakage currents occur.

The technical result and industrial applicability of the invention is to provide an indication of the increased level of dust deposition, as well as turning off the electronic equipment when the maximum threshold for wet dust deposition is reached by an optical-electronic two-wave two-channel method.

A known optical dust meter (Klimenko AP et al. "Continuous monitoring of dust concentration. Kiev, Technics, 1980, p.77-79) containing a control photodetector, the light to which is scattered at an angle of 45 ° from the sight glass and then signals about the limit value of dust.

The disadvantages of the device include the lack of control of humidity in the dust deposition, the presence of which increases the likelihood of leakage currents in electronic equipment.

Known dust and smoke sensors (detectors), operating on the principle of periodic emission of light pulses and the subsequent reception by the photosensor of light reflected from smoke particles. The signals (current or voltage) from the photosensors are amplified using various analog amplifying devices (transistor stages, operational amplifiers, etc.) and compared with the reference signal, as a result, a signal is issued indicating the presence or absence of smoke. The emitted and received pulses can be modulated, compared and processed in various ways that contribute. some increase in sensitivity and noise immunity (see US Pat. RU 2134907 G08B 17/10 dated 08/20/99, RU 2125739 G08B 17/10 dated 01/21/99, RU 2006837 G01N 21/85 dated 08/12/91, RU 2095792 G01N 21/85 dated 11/08/95).

The disadvantages of the devices include the lack of the ability to control humidity in the dust deposition, the presence of which increases the likelihood of leakage currents in electronic equipment.

Known optical dust concentration meter (US Pat. SU 1283629 A1, G01N 21/47 from 01/15/87), containing two light emitters included in the measuring and control channels that operate in the infrared region of the optical spectrum, in a pulsed mode and at different frequencies. The light emitters are optically coupled to a photodetector located in one housing with them through spherical mirrors, a working chamber, a light filter and through a spherical mirror and a light filter, respectively. Synchronous detectors from the amplified voltage of the light detector emit signals from the control and measuring channels. The signal of the control channel is compared with the reference signal, and the output signal of the measuring channel is corrected by the magnitude of their difference.

The disadvantages of the device include the lack of control of humidity in the dust deposition, the presence of which increases the likelihood of leakage currents in electronic equipment.

A known method of detecting dust deposition (US Pat. RU 2426982 G01N 21/94 from 01/10/2011), selected as a prototype. The principle of operation of the device according to this method is as follows:

- alternately emitted light pulses;

- photo pulses are received by light pulses reflected at an angle to the optical axis of the radiation;

- light pulses arrive at the microcontroller and are compared by subtracting S (t ₁ ) -S (t ₂ ) = k with the given values, which are used to judge the dustiness of electronic equipment.

The disadvantages of the prototype include the lack of the ability to control humidity in the dust deposition, the presence of which increases the likelihood of leakage currents in electronic equipment.

The objective of the proposed invention is the detection of increased dust deposition taking into account humidity by the optoelectronic method, in which leakage currents can occur, leading to failure of the electronic equipment.

The problem is solved by the method of detecting dust deposition, taking into account the level of humidity on the printed circuit boards of electronic equipment, consisting in the fact that light pulses are periodically emitted by two LEDs with a wavelength of minimum radiation absorption λ ₁ = 565 nm (to take into account the level of dust deposition) and two LEDs with a long wavelength the maximum water absorption of the radiation λ ₂ = 930 nm (to account for the level of wet pyleotlozheniya) and received as reflected by the three plates, the first plate has artificially n worn maximum pyleotlozheniya, the second is in a sealed housing with artificially created maximum level pyleotlozheniya with limit threshold humidity, and the third is a control plate, a photosensor, the photosensor detects first light pulses of the two LEDs having a wavelength λ _1, then the light pulses of the two LEDs with length wavelength λ ₂ entering at an angle to the optical axis of radiation, comparing them by subtraction, resulting in the detection of elevated levels pyleotlozhe tions and the presence of wet pyleotlozheniya.

Figure 1 presents a block diagram of a device that implements the proposed method. Figure 2, figure 3 schematically shows the design of the sensor.

The proposed device of FIG. 1 contains LEDs 1, 2, 3, and 4, optically coupled via mirrors 12 to a photodetector 8, which is connected to the microcontroller port 9, a signaling device 10 and a threshold load disconnecting device 11, plates 5, 6, and 7.

The operation algorithm of the device of figure 1 consists of the following steps.

Light pulses are alternately emitted by pairs of LEDs 1, 3 (dust control channel with LED wavelength λ ₁ = 565 nm) and 2, 4 (wet dust control channel with LED wavelength λ ₂ = 930 nm). Light pulses reflected at an angle to the optical axis of radiation from the plates 5, 6 and 7, reflected from the mirrors 12, are alternately received by the photosensor 8, after which the pulses are transmitted to the microcontroller 9. The plate 5 has the highest possible dust level artificially applied, the plate 6 is sealed case with artificially created maximum dust level with a maximum humidity threshold, plate 7 - a clean plate of the control channel.

The pulses from the LEDs 1 (S ₁ (t)) and 3 (S ₃ (t)) arrive first and are stored by the microcontroller 9, after which the pulses from the LEDs 2 (S ₂ (t)), 4 (S ₄ ( t)), and then they are compared by subtraction. If (S ₁ (t) -S ₃ (t)) ≥0 and (S ₂ (t) -S ₄ (t)) ≥0, then microcontroller 9 sends a signal to LEDs 1, 2, 3, 4 and the cycle starts again. If (S ₁ (t) -S ₃ (t)) <0, then the microcontroller 9 includes an indicator 10, which is used as an LED, and if (S ₂ (t) -S ₄ (t)) <0, then microcontroller 9 includes a threshold load disconnect device 11.

Plates 5, 6 and 7 (Figs. 1, 2) are made of the same material as the printed circuit board of electronic equipment (textolite, fiberglass, getinax, polyimide, fluoroplastic, etc.).

Thus, the proposed method allows to provide an indication of the increased level of dust sedimentation, as well as turning off the electronic equipment when reaching the maximum threshold for wet dust deposition.

Claims (1)

A method for detecting dust deposition, taking into account the level of humidity on printed circuit boards of electronic equipment, consisting in the periodic emission of light pulses by two pairs of LEDs and receiving these pulses reflected from the plates by a photosensor, while one of the plates has an artificially applied maximum level of dust deposition, and the photosensor alternately registers both reflected light fluxes from two channels arriving at an angle to the optical axis of radiation, comparing them by subtraction, characterized in that then two LEDs with a wavelength of λ ₁ = 565 nm are used to control the level of dust deposition, and two LEDs with a wavelength of λ ₂ = 930 nm, a photosensor with spectral sensitivity in this area, a threshold load disconnect device at a critical humidity level are used to account for wet dust deposition , an additional plate located in a sealed enclosure with an artificially created maximum level of dust deposition with a maximum humidity threshold, as a result of which an indication of an increased level of dust deposition occurs Iya, as well as turning off the electronic equipment when reaching the limit threshold of wet dust deposition.

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