AND WILL RELAY SAFEElectronic devices and components, in the terminal stages which employ electromagnetic relays, to this day has not lost its relevance among radio Amateurs. Despite competition from thyristors and optoelectronic devices, circuits control the load devices remain niche where the solenoid is indispensable. Their popularity among radio Amateurs due to the low cost, versatility (multiple groups of contacts), high reliability, compactness of the housing. Therefore, the use of low-power relay becomes the optimal solution when switching electronic components medium to high power high-voltage electric circuits (in the limited dimensions of the devices).

For starters, take a look at models manufactured by a domestic low-power relays. They are divided into three types.
1. With one group of switching contacts
RES 10 (passport RS4.524.302, RS4.504.314, RS4.504.319), RES 15 (passport RS4.591….003 006, ХП4.591…. 010 014), RES 34 (passport RS4.524.372, RS4.524.376), RES 49 (passport RS4.569.000, RS4.569.423, 424) and others.
2. With two groups of switching contacts
RES 6 (passport RF0.452.10…104), RES 9 (passport RS4.524.200…201, RS4.524.209, RS4.524.213), RES 37 (passport RF4.510.064, RF4.510.072), RES 47 (passport RF4.500.408, RF4.500.417), RES 48 (passport RS4.590.201, RS4.590.207, RS4.590.213, RS4.590.218), RES 54 (ХП4.500.010…011), and others.
3. With four groups of changeover contacts: RES 22 (passport RF4.500.131, RF4.500.163, RF4.500.225, RF4.500.231), RES 32 (passport RF4.500.342…343, RF4.500.354…355) and others.
All of these electromagnetic relays are rated for a trigger voltage of 10 to 20 V. you Can include in the electric circuit and with slightly higher voltage (to 30 V) in series with the relay coil, connect a limiting resistor of MLT type with a capacity of at least 1 watt. However, if voltage more than 30 V, the application of such relays is impractical: increasing total current, limiting resistor generates a large amount of thermal energy in the initial moment of applying voltage to the coil of power surge may bring the relay down.
For all the electromagnetic relays used in electrical circuits, the defining parameters are the resistance of the winding, the actuating current and the number of contact groups. These settings are specified in the passport to each device.
When designing electronic devices or replacement solenoid should be aware that the trigger voltage of the relay (the mathematical product of resistance to current consumption) should be 20…30% less input voltage. This is required for reliable commutation of the Executive relay contacts, stable ability to attract and retain the anchor in terms of possible vibrations of the device.
Electric current flowing through the relay coil must not exceed the maximum collector current of the switching transistor.
When connecting low-power relay in the electric circuit of 220 V complications can occur due to overloads during operation a specific node with a subsequent failure of the relay. To avoid this, in the circuit to provide a special decoupling the console. Electrical diagrams of two such nodes are shown in the figure.
Circuit diagrams of the decoupling consoles to manage powerful load up to 600 VDC (a) and AC load (b)
A circuit diagram of the decoupling consoles to manage powerful load up to 600 VDC (a) and AC load (b)
Figure 1(a) the scheme of management powerful load up to 600 V with a thyristor VS1. Is specified in the scheme of the device can be applied КУ201, КУ202 with literal indexes To — N. The diode bridge is replaced by КЦ402А, KTS405 with a permissible reverse voltage of at least 150 V. the Resistor R1, the type of MLT, limits the current in the circuit control electrode of the thyristor. This diagram of the load ensures the supply of direct current, rectified by a diode bridge VD1 — VD4. If the load capacity does not exceed 100 W and the duration of its connection is not large (not more than 1 hour), the thyristor can not install on the radiator. Heating of the case VS1 for example in the range of 40 — 60 degrees Celsius. In other cases, the thyristor VS1 should be installed on cooling radiator or heat sink aluminum plate with an area of 36 — 50 cm2. The heat sink must be insulated from the body of the device. In the operation of this site should be considered a permanent type of current acting on the load. For example, connecting the load of an electric lamp at 220 V will be justified, and a transformerless power supply with the extinguishing voltage capacitors — no.
For devices AC loads fully fit electronic node whose schema is shown in figure 1(b). The control element used here is a triac КУ208Г (can be replaced by КУ208В). Thanks to the use of the triac (or equivalent — a pair of counter-connected thyristors), eliminating the need for the rectifier. Case КУ208 identical to the body of the thyristors КУ201. Setting it on the radiator is subject to the same conditions as in the previous scheme. Through the use of these devices, low-power contacts relay type РЭС10, РЭС15 sensitive to power surges into a powerful switched load, be safe, since the current flowing through contacts K1.1, will not exceed 20 — 30 mA.
In the operation of components and devices affected by life-threatening voltage 220 V, care must be taken and safety measures — do not touch the elements included in the network device, the installation work only be performed with disconnected voltage.
A. KASHKAROV, St. Petersburg

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