Retarder for turning on an incandescent lamp. Encyclopedia of radio electronics and electrical engineering

Encyclopedia of radio electronics and electrical engineering / Lighting

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It is known that incandescent lamps are short-lived. They, as a rule, fail at the moment of switching on, when a large current flows through the cold filament of the lamp, or with a significant increase in the mains voltage. As practice shows, an increase in voltage by 10% reduces the life of a 100 W lamp by almost 6 times, and a decrease by 15% increases it by 10 times.

To extend the life of the lamp will allow the machine, the diagram of which is shown in Fig. 1. Immediately, we note that in parallel with the EL1 lamp shown in the diagram, it is permissible to turn on several loads in the X2 socket, the power of which, together with EL1, does not exceed the allowable for the triac VS1. The machine can also be used to power one or two expensive powerful lamps, for example, used to illuminate photographed objects. In this embodiment, it will bring greater economic benefits than with the protection of conventional incandescent lamps.

Mains voltage is supplied to the device through switch SA1 and a fuse. A chain of resistor R1, capacitors C1 - C3 and inductor L1 is a noise suppression filter. The power part of the machine consists of a triac VS1, dinistors VD3, VD4, resistors R7 - R10, capacitors C5 and Sat. The control unit includes transistor VT1, diode VD1, zener diode VD2, optocoupler U1, resistors R3 - R6, capacitor C4. The inclusion of the machine in the network is signaled by the LED HL1.

This device performs three functions. Firstly, it ensures smooth ignition of the lamp, and at the first moment the warm-up process should be longer. On fig. 2 it can be seen that in the range from 0 to 90 V, when the thread starts to heat up, this interval is 6 s, and the rest of the voltage rises to 220 V in 3...4 s. It is also possible to manually adjust the brightness and smooth extinction of the lamp.

As mentioned above, it is advisable to limit the load voltage to 200 V, which will significantly increase the lamp life. Its smooth extinction occurs when the contacts of the SA2 switch are opened.

The machine works like this. When the contacts of the SA1 switch are closed, the voltage rectified by the VD1 diode is supplied to the charging circuit, consisting of resistors R3, R4, R5 and capacitor C4. Switch contacts SA2 must be open. At the first moment, the field effect transistor VT1 is closed, the lamp EL1 is off. To protect the transistor from breakdown, a Zener diode VD2 is installed. The duration of charging the capacitor C4 is determined by the resistance of the resistors R4 and R5, the resistor R3 limits the voltage drop across the capacitor C4.

After closing the contacts of the switch SA2, the voltage across the capacitor C4 begins to rise, the lamp EL1 lights up smoothly, since the transistor VT1 begins to open, the voltage increases at pins 1 and 3 of the optocoupler U1, and the dark resistance of the built-in photoresistor (pins 2,4) starts to decrease, which leads to the opening of the triac VS1. The final voltage EL1 is determined by the resistance of the resistor R8: the larger it is, the lower the voltage on the lamp. The brightness of the lamp after it is turned on is set by a variable resistor R9. At any position of the resistor slider, the machine will smoothly turn on and off the lamp. But in order to turn off the lamp, it is necessary to put the switch handle SA2 in the position of open contacts. In this case, the voltage across the capacitor C4 begins to gradually decrease and the lamp goes out completely. For long breaks, the voltage should be removed with the SA1 switch.

The machine uses resistors with a power of 0,25 W, and R2, R6, R7 - 2 W. Variable resistor - any type with characteristic A. Capacitors C1-C3, C5, C6 - K73-17, and C1-C3 must be at a voltage of at least 400 V, and C5, C6 - at 63 V. Capacitors K73-11 are applicable, K75-10 or, as a last resort, MBM, MBGO, MBGCH. Capacitor C4 - K50-35 or K50-6. In addition to those indicated in the diagram, the transistor can be KP304A, the triac - KU208G (it is installed on a heat sink with a surface area of ​​10,16, 25 or 65 cm2 at a load power of 200, 300, 500 or 1500 W, respectively). LED - AL102B, diode VD1 - D226V, KD209A, dinistors can be replaced with one KR1167KP1B chip. Switch SA1 - any type for a voltage of 250 V and a current determined by the power of the EL1 lamp and other loads; switch SA2 - any type, for example PD-9-2. Instead of the optocoupler OEP-12, OEP-2 or similar with a light resistance of not more than 1000 ohms is suitable. Inductor L1 is wound on a rod with a diameter of 8 and a length of 40 mm made of ferrite 400NN wire PEV-2 0,51 and contains 215 turns.

Before tuning, instead of resistors R3-R5, R8, R10, it is necessary to solder trimmers with a resistance of 1 MΩ. In this case, the sliders of resistors R3, R8, R9 should be placed in the position of minimum resistance, and R4, R5, R10 - in the middle position. Turn on a real lamp as a load. Connect a tube voltmeter to the terminals of capacitor C4, and a DC voltmeter to terminals 1,3 of the optocoupler. Using LATR, apply voltage to the machine. The lamp should not burn.

With a mains voltage of 220 V, the current consumption of the machine is approximately 8 mA.

Gradually increasing the resistance of the resistor R3, observe an increase in the voltage at pins 1, 3 of the optocoupler up to 1,2 V. Depending on the spread of the transistor parameters, the voltage should be such that the transistor is on the off-on border. Next, close the contacts of the SA2 switch and observe the rate of increase in the voltage at the 1,3 optocouplers to 1,8 V. In this case, the EL1 lamp should light up slowly, and the voltage on it should reach 220 V. The ignition speed of the lamp depends on the resistance of the resistor R5. To slow the lamp on, the resistance of the resistor must be increased, and vice versa. Resistors R3, R4, R5 are interconnected, so they should be carefully selected.

After that, open the contacts of the SA2 switch and observe the rate of lamp extinction. To increase it, it is necessary to increase the resistance of the resistor R4, and vice versa. Thus, the resistor R4 together with R5 determines the rate of extinguishing the lamp, the resistor R5 determines the ignition rate, and R3 determines the boundary between the on-off state. A clear extinguishing of the lamp is achieved by selecting a resistor R10. Next, by selecting resistor R8, set the voltage on the lamp to about 200 V at a mains voltage of 220 V, and then check the manual brightness control with resistor R9.

If manual adjustment is not used, it is permissible to put a jumper instead of resistor R9.

In conclusion, I note that the slower the ignition rate of the lamp, the closer it is to "eternal", especially if the lamp is of high power.

Author: R.Balinsky, Kharkov, Ukraine

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