Phototransistor smoke detector. Scheme, description

Free technical library

ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING
Free library / Schemes of radio-electronic and electrical devices

The phototransistor is a smoke detector. Encyclopedia of radio electronics and electrical engineering

Free technical library

Encyclopedia of radio electronics and electrical engineering / Security devices and object signaling

Comments on the article

In a fire-fighting device, the principle of operation of which is shown in Fig. 1, a field effect phototransistor having a high sensitivity to changes in illumination is used. The luminous flux from the lighting lamp L1 passes parallel to the window of the phototransistor, and in the absence of smoke, no current flows through the phototransistor.

Phototransistor - smoke indicator
Ris.1

The appearance of even faint smoke causes light to scatter, some of which enters the phototransistor window. The collector current increases under the influence of the luminous flux, the executive relay R is activated, which turns on the power supply circuit of the device that gives the alarm signal with its contacts.

For similar purposes, an ordinary phototransistor can be used, which is an integral part of a trigger assembled according to the circuit in Fig. 2.

Phototransistor - smoke indicator
Ris.2

Light control in this device is as follows. In the standby state, transistor T1 is lit, current flows through it, no current flows through transistor T2 and the relay winding P1. Dimming the light output reduces the current through the phototransistor. Transistor Tg goes into saturation mode, its collector current triggers the relay and closes the contacts in the power supply circuit of the signaling device.

From the editor. The TEC field phototransistor has no replacement, the OCP70 transistor. is replaced by the domestic transistor FT-1, AS126 on MP41A. Diodes D1-D3 (OA200) can be replaced with D226D.

The active resistance of the relay winding must not be less than 350 Ohm, and the operation current must not be more than 40 mA.

Literature

"ToufeI Electronigue", 1969, No. 332.
Radio No. 2 1970

Publication: N. Bolshakov, rf.atnn.ru

See other articles Section Security devices and object signaling.

Read and write useful comments on this article.

<< Back

Latest news of science and technology, new electronics:

Artificial leather for touch emulation 15.04.2024

In a modern technology world where distance is becoming increasingly commonplace, maintaining connection and a sense of closeness is important. Recent developments in artificial skin by German scientists from Saarland University represent a new era in virtual interactions. German researchers from Saarland University have developed ultra-thin films that can transmit the sensation of touch over a distance. This cutting-edge technology provides new opportunities for virtual communication, especially for those who find themselves far from their loved ones. The ultra-thin films developed by the researchers, just 50 micrometers thick, can be integrated into textiles and worn like a second skin. These films act as sensors that recognize tactile signals from mom or dad, and as actuators that transmit these movements to the baby. Parents' touch to the fabric activates sensors that react to pressure and deform the ultra-thin film. This ... >>

Petgugu Global cat litter 15.04.2024

Taking care of pets can often be a challenge, especially when it comes to keeping your home clean. A new interesting solution from the Petgugu Global startup has been presented, which will make life easier for cat owners and help them keep their home perfectly clean and tidy. Startup Petgugu Global has unveiled a unique cat toilet that can automatically flush feces, keeping your home clean and fresh. This innovative device is equipped with various smart sensors that monitor your pet's toilet activity and activate to automatically clean after use. The device connects to the sewer system and ensures efficient waste removal without the need for intervention from the owner. Additionally, the toilet has a large flushable storage capacity, making it ideal for multi-cat households. The Petgugu cat litter bowl is designed for use with water-soluble litters and offers a range of additional ... >>

The attractiveness of caring men 14.04.2024

The stereotype that women prefer "bad boys" has long been widespread. However, recent research conducted by British scientists from Monash University offers a new perspective on this issue. They looked at how women responded to men's emotional responsibility and willingness to help others. The study's findings could change our understanding of what makes men attractive to women. A study conducted by scientists from Monash University leads to new findings about men's attractiveness to women. In the experiment, women were shown photographs of men with brief stories about their behavior in various situations, including their reaction to an encounter with a homeless person. Some of the men ignored the homeless man, while others helped him, such as buying him food. A study found that men who showed empathy and kindness were more attractive to women compared to men who showed empathy and kindness. ... >>

Random news from the Archive

Self-cleaning film repels bacteria 15.12.2019

A team of researchers from McMaster University (Canada) has developed a film that can repel all forms of bacteria, including those resistant to antibiotics. It can be used as packaging for food and medical instruments, as well as a protective coating for door handles and railings.

The new plastic surface is an improved form of conventional transparencies. The material is covered with microscopic "wrinkles", due to which substances - for example, a drop of water or blood - do not stick to the surface of the film, but bounce off it. This texture also prevents the formation of a biofilm of harmful bacteria.

The researchers tested the material using two forms of antibiotic-resistant bacteria: Staphylococcus aureus (MRSA) and Pseudomonas aeruginosa. The material demonstrated its repulsive ability by 87% in the case of the first pathogen, and by 84% in the case of the second. E. coli also failed to move to new material after it came into contact with another - infected - surface.

Other interesting news:

▪ Insects became small, escaping from birds

▪ Apacer AH650 Flash Drive with Capacitive Fingerprint Sensor

▪ Music for aliens

▪ Safe fuel will not ignite when in contact with fire

▪ Humanoid robot will go into space

News feed of science and technology, new electronics

Interesting materials of the Free Technical Library:

▪ section of the site Data transfer. Article selection

▪ the article is not worth a penny. Popular expression

▪ article Because of what legend did William Burroughs' wife die? Detailed answer

▪ article Hall Administrator (Maitre d'). Job description