FIRE BURN

The most costly part of the device — infrared detector (IR) — costs about 80 rubles. But it can be used from the old remote control receiver (remote control) installed in the TV. Such detectors began to recruit colored television back in the late 80-ies of the last century, fit and taken from the detector (receiver Board do not need). Modern TVs also have a similar IR detectors — and they will fit for the design.

The supply voltage of the device is in the range from 5 to 7 due to the technical characteristics of the IR sensor. The supply voltage can be increased, for example up to 12, adding a simple circuit limiter-regulator consisting of a Zener diode КС156А (or similar, for example ВZХ55С) and included with it consistently limiting resistor with a resistance of 0.82—1 com. The anode of the Zener diode is connected to the common wire, and a connection point of the Zener diode (cathode) and a resistor connects to pin 2 of the sensor IF1. The supply voltage is fed to the limiting resistor. The current consumption of the device does not exceed 25 mA, 20 mA, of which “picks up” the sound capsule.

 

The principle of operation

 

Oxide capacitor C1 smooths out the noise on nutrition. The normal state is sensitive the IR detector is a small high level at the output (pin 3 IF1). If the area of the “responsibility” of the detector there is IR signal on pin 3 of the detector contains negative pulses. The polar capacitor C2 is used to reduce the influence of random and extraneous interference. It is particularly necessary when in the same room there is a radio remote control (usually they use the IR spectrum for signal transmission to a distance of, for example, the alarm device installed in the living room and controls the operation of the fireplace). If the device is used in the bath (and where such interference is unlikely), C2 is advisable to exclude from the scheme of Negative pulses of small amplitude insufficient to control sound (and light) alarm device or relay. Therefore, passing a peak detector on elements R1, VD1, they arrive at the gate of a field effect transistor VT1, acting as a current amplifier. The transistor controls the sound output level with the built-in generator audio frequency (AF) — NA1.

 

 

Ready alarm device in a housing

 

At the end of the firebox of a fireplace alarm can be turned off by a switch SV1.

 

The device is in adjustment is not needed. The oxide capacitor C3 in this circuit is the element providing a delay turn off the sound. This is to ensure that the signaller did not respond to a flickering flame or a momentary decrease in the burning. So managed to achieve that “alarm” will sound only when the flames will really fade. The larger the capacitance of the capacitor C3, the greater the inertia of alarm will be reached. In a very narrow range of sensitivity of the device can be adjusted by changing the resistance of the constant resistor R1.

 

Details

 

An infrared detector РRМ6936 can be replaced by ТЅОР1736СВ1 or similar. Conclusions in order I think, drawing detector convex side facing you. The device ТЅОР1736СВ1 1 and 2 conclusions are nearby, then using 2 mm from the second comes the third. A polarity detector enable is not allowed.

Electrolytic capacitors of the type K50-29 or similar. A field-effect transistor ВЅТ70 can be replaced by ВЅ170 or the like. Both resistor — type MF-25. Diode VD1 can be replaced by KD522, Д220, KD503 with any alphabetic index or foreign equivalent 1N4148. Sound capsule NA1 with built-in AF generator at any voltage 3 — 6V, for example TR-1203Y. Capsule be sure to include as indicated on the polarity diagram. Instead of, or in parallel with it you can turn even low-current electromagnetic relays with a supply voltage of 5 V, for example TRU-5VDC-SB-SL. This solution can be useful for the future (see text below).

 

 

The electrical circuit of the electronic alarm device

 

Elements in the circuit so small that the PCB I designed, implemented a standard perforated “billet” metalized holes in the conclusions, and the inter-connections are made using wire MGTF-0,6. The photo shows the hull ready indicator (on the right — earpiece-alarm HA1).

 

Features and prospect of use

 

The device responds well to an open flame; at a distance of 0.5 m, the alarm is triggered even in a lighted match. From this we can draw a simple conclusion that on the basis of the proposed device can produce a fire detector. The principle of operation is the same from open flame, and the efficacy of the operation of the indicator is the same as that night: because the device does not respond to light, not for heat, not for the flickering flames, and the infrared component in the spectrum of fire, and it is the time of day depends Especially need such a detector may be outdoors, in open spaces, in forests, in towns, on the street. In these areas conventional fire detector responsive to smoke, are practically useless. In cases when you want to manage powerful load (current up to 6 A at 220 V), the load should be connected across the relay. For example, a submersible water pump.

 

The device can also be useful for controlling the operation of all remote controls (“catches” both direct and reflected off the walls “invisible” to man the IR beam); for Troubleshooting and monitoring the operation of computer peripherals and cellular phones with infrared port; for the “monitoring” space, the vault, which may be installed invisible man, alarms, triggered when crossing the infrared beam (like in the movies about the agent 007) and in many other cases. The device is simple to build.

 

A. KASHKAROV, St. Petersburg