Automatic protection of network radio equipment. Scheme, description

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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING
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Automatic protection of network radio equipment. Encyclopedia of radio electronics and electrical engineering

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Encyclopedia of radio electronics and electrical engineering / Clocks, timers, relays, load switches

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The device is designed to prevent overload and malfunctions in radio equipment due to the deviation of the mains supply voltage beyond the tolerance. It will be especially useful in the country or in the countryside, where significant voltage fluctuations in the network are not uncommon. Often used in unstable networks, ferromagnetic stabilizers have a narrow stabilization range and, with significant voltage fluctuations (in the direction of increase), they simply fail. For some radio equipment, not only high, but also low mains voltage is dangerous.

To control the network with a measuring device, each time before turning on the radio devices, is inconvenient and inefficient, since a deviation can occur during operation. But this task can be taken over by an automatic control device, through which the equipment is powered.

Rice. 1.34 (click to enlarge)

Rice. 1.35 (click to enlarge)

When the device is initially turned on (using the SB1 button), it checks the mains voltage level for one second to see if it is within the tolerance of 170 ... 260 V, as well as for interference. If the voltage deviates beyond the tolerance, the circuit will not allow you to turn on the radio equipment.

Automatic protection of network radio equipment
Rice. 1.36. PCB topology for node A1

During the operation of the protective device, the circuit continuously monitors the state of the network, and when the voltage goes beyond the tolerance of 190 ... 245 V, an audible alarm starts working, warning that it is better to turn off the radio equipment. At the same time, by the glow of the LED indicator, you can determine the type of voltage deviation in "+" (increase) or "-" (decrease). In the event of a dangerous mismatch in the mains voltage (when the tolerance of 170 ... 260 V is exceeded), the radio equipment connected to the sockets X1, X2 will turn off automatically.

The electrical circuit of the device is shown in fig. 1.34 and 1.35 and consists of a four-level comparator on the elements of the D2 chip, a sound generator on the elements D3.1 ... D3.3, a switching unit on a transistor and relay K1, as well as a power supply unit with a voltage regulator on the D1 chip.

The comparator response threshold is set during tuning by resistors marked with an asterisk "*" in the diagram. Their values are indicated on the diagram approximately. The device is configured using LATRA by changing the supply voltage on the XP1 plug. At the same time, we set the threshold exceeding 15 V with resistor R245 (log "2" appears at the output D8/1), and the voltage drop below 14 V with resistor R170 (log "2" at output D8/0). It is convenient to use multi-dimensional adjusting resistors for tuning.

It is better to start setting up the circuit by checking the operability of the node shown in Fig. 1.34. When you press the ON button (SB1), relay K1 is activated with a delay of about 1 second and contacts K1.2 blocks the button. The delay time for turning on the relay depends on the value of the capacitance C2 and the resistor R7. Switching off relay K1 can be done with the OFF button (SB2) or from the automation circuit, when a pulse or log appears at the output of the D3 / 11 chip. "1" (when the voltage goes beyond the tolerance).

On fig. 1.36 shows the topology of the printed circuit board for the circuit section (A1), highlighted by a dotted line. The rest of the circuit is made on a universal prototyping board by volumetric wiring.

The circuit uses capacitors C1 ... C4 type K52-16 for 63 V; C5, C6 - K10-17. Resistors and diodes will fit any similar ones. Transformer T1 is best used from the unified CCI series. It must provide a voltage of 22 ... 24 V and a current of at least 60 mA in the secondary winding.

Relay K1 is used of the RES48 type (passport 4.590.201), but many others are also suitable, with an operating voltage of 24 V.

The automatic protection device can be simplified if the sound and light signaling of voltage deviations is abandoned. In this case, the voltage level control circuit in Fig. 1.35 we replace the one shown in fig. 1.37. It consists of transistors operating in microcurrent mode. In the normal state, with trimmers R12 and R15, we set a log on the collectors VT2 and VT3. "0" and log. "1" respectively. In this case, the transistors VT4 and VT5 are locked and there is no voltage on the resistor R19 (VS1 will work when it appears).

By changing the mains voltage using LATRA, with the resistor R12 we set the threshold for the operation of the circuit at a voltage below 170 V, and with the resistor R15 - when it exceeds 260 V.

Automatic protection of network radio equipment
Fig. 1.37

When using the second version of the scheme, block A1 is also simplified. In this case, the stabilizer D1 is not needed, and if the transformer T1 has a free winding for a voltage of 6 ... 12 V, then it can be connected to circuits 5 and 6 (instead of resistors R1 ... R3, install jumpers, exclude R4 and R10 from the diagram).

Publication: cxem.net

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