Simple emergency light source

Description of the scheme and principle of operation of a simple emergency lamp based on an energy-saving lamp.

There are situations when during a power outage it is necessary that some area remains lit. For example, it can be a corridor, utility room, or just a workplace. In this situation, an emergency lamp made on the basis of a conventional energy-saving lamp with a power of not more than 9 - 11 watts will greatly help.

When the mains voltage is normal, the lamp works directly from the mains. In the event of a power failure, the lamp switches to battery power. In normal operation, the battery is recharged from the network, thereby maintaining the constant performance of the lamp. The schematic diagram of such a lamp is shown in Figure 1.

Emergency light operation in normal mode

A bridge rectifier VD3 connected through a ballast capacitor C3 is used as a detector for the presence of mains voltage. Resistor R2 is designed to limit the current at the time of charging capacitor C6. This capacitor is designed to smooth the ripple of the rectified mains voltage. LED HL1 acts as an indicator of the mains voltage, through it also connected in series windings of relay K1.

As can be seen from the diagram, the relay will be turned on only if there is voltage in the network and the closed switch SA1.1. The second contact group SA1.2 is designed to connect the battery GB1 to the voltage Converter.

Mains voltage Via contact K1.1, it enters the lamp EL1 and the primary winding of the transformer T1. In this state (relay K1 is on), the contacts of relay K1.3, K1.4 connect the secondary winding of transformer T1 to the rectifier on diodes VD1, VD2, made according to the voltage doubling circuit. This voltage is obtained at capacitors C4, C5 and is used to power the battery charger.

Figure 1. Scheme of the emergency lamp.

Battery Charge Scheme

The charging device consists of a controlled current source collected on an adjustable integrated stabilizer DA1 type KR142EN12A. The maximum charging current is limited by the resistance of the resistor R3, and at the values ​​indicated on the diagram it is 120 - 130 mA. An asterisk in the diagram next to the designation of this resistor means that you may need to select it during setup.

On the DA2 parallel stabilizer, a charging process control unit is assembled. When the battery voltage is small, the DA2 stabilizer is closed, the HL2 LED shines very weakly, almost does not shine, the battery will be charged with maximum current.

The battery voltage during charging will gradually increase, and through the divider R5, R6 act on the control electrode of the stabilizer DA2. As soon as the voltage on this electrode exceeds 2.5 V, an increase in the cathode current of the stabilizer begins (pin 3 of DA2). The brightness of the LED HL2 increases, and the charging current will decrease. The brighter the LED shines, the lower the charging current. Therefore, the charging current gradually decreases and constantly maintains the battery in a charged state. This is how this device behaves when there is voltage in the network.

The device is in emergency mode

When the voltage disappears, the relay coil K1 is de-energized and it returns to its original position, as shown in the diagram. The positive battery terminal is connected to the generator via relay contact K1.2. But along with this, one should not forget that the network switch SA1 will remain on (in the diagram it is shown in the “Off” position), and its contact group SA1.2 already connects the negative terminal of the battery to the generator, which is made on the DD1 chip.Thus, the voltage from the battery will be supplied to the generator.

The generator will begin to produce pulses with a frequency of about 50 Hz, which control the operation of a power amplifier assembled in a bridge circuit on transistor assemblies VT1, VT2.

The secondary winding of the transformer T1 will be connected to the output of the bridge amplifier through the relay contacts K1.3, K1.4, as shown in the diagram. In this mode, the transformer works as a boost and powers the EL1 lamp. The lamp continues to light, receiving power from the battery.

The contact of the relay K1.1 is open at this time, so the voltage from the transformer to the rectifier VD3 does not reach, and the relay K1 remains off. When the mains voltage appears, relay K1 will turn on through the rectifier VD3, and normal operation of the device will be restored.

The battery is composed of seven AA batteries with a capacity of 1000 mAh. When using an EL1 lamp with a power of 11 W, such a battery lasts for 45 minutes of operation of the lamp. If you need more battery life, just install a larger battery.

Setting up an emergency lighting device

Setting up the device is easy. It should start with setting the battery charging current, for which you should connect the device to the network with a fully charged battery. Using the trimming resistor R6, set the charging current of the battery within 0.5 - 1.0 mA.

After that, disconnect the unit from the network, the generator should start. The frequency of the generator should be about 50-60 Hz. You can adjust the frequency by selecting the resistor R1.

The voltage at the output of the converter, in the case of using an energy-saving lamp, at digital multimeter M-832 should be in the range 280 - 305 V. Such a seemingly high voltage, instead of 220 - 240 V, is explained by the rectangular shape of the pulses at the converter output when the lamp is in emergency mode.

If an incandescent lamp is to be used, then the output voltage of the converter should be set between 200 - 215 V.

The necessary voltage at the output of the converter can be achieved by changing the number of turns of the secondary winding of the transformer. It is not difficult to make such a setting, if the transformer has a collapsible design, the secondary winding is located on top of the primary or on a separate coil.

Parts and construction

The entire electronic unit can be assembled on a board made of foil fiberglass 1.5 mm thick. A possible version of the board is shown in Figure 2.

Figure 2. The printed circuit board of the electronic unit of the lamp.

The board is designed to install resistors such as MLT-0.125, trimming resistor R6 type SP3-19a. Imported electrolytic capacitors with a working voltage not lower than indicated on the diagram. Capacitors C2 and C3 are film type K73-17, the capacitor C7 is small-sized ceramic.

Relay K1 type RKM-1, its operation voltage when the windings are connected in series (as shown in the diagram) 24 V at a trip current of about 25 mA. As a replacement, any relay with the same contact diagram, coil voltage and tripping current, for example, imported TRY-24VDC-P4C, is suitable.

The relay coil is powered through a rectifier VD3, the current through which is limited by a ballast capacitor C3. Its capacity should be selected so that the current supplied by the rectifier in the short circuit mode is slightly larger than that required for the relay to operate. For the applied relay, this current is 30 mA. If a different type of relay is used, the capacitor C3 will have to be selected.

The maximum allowable current of the HL1 LED type KIPMO1G-1L according to the technical conditions of 60 mA. Therefore, through it, without fear, you can connect the relay coil K1. This LED can be replaced with any red glow. To reduce the current through the LED to an acceptable value, he will have to connect a resistor with a resistance of 150 - 200 Ohms in parallel.The HL2 LED can be replaced with any green glow, and no modifications are required.

The T1 transformer is used from a network adapter. At a load current of about 1 A, the voltage of the secondary winding should be about 9 V, and the secondary winding is made with a wire with a diameter of at least 1 mm. The dimensions of the transformer must be such that it can fit on the board.

The finished board is installed in a case of suitable size, in which it is necessary to make holes for the LEDs. To connect the lamp, install an electrical outlet in the device. If the electronic unit is part of the lamp, then you can install the usual standard cartridge in the same housing.

Boris Aladyshkin