Dimmable LED night light. Scheme, description

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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING
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Dimmable LED night light. Encyclopedia of radio electronics and electrical engineering

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Encyclopedia of radio electronics and electrical engineering / Lighting

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Modern ultra-bright white LEDs allow you to assemble a compact device for soft nighttime room lighting (Fig. 3). Since this design does not contain incandescent lamps, it is not afraid of drops, power surges and other nuances inherent in devices with incandescent lamps.

Dimmable LED night light
Fig. 3

When the night light is connected to the network (through the XP1 plug), the supply voltage, the excess of which is quenched by the capacitor C1, flows through the protective resistor R1 to the diode bridge VD1. The rectified voltage is stabilized by the zener diode VD2 and is fed through resistors R3 and R4 to a chain of series-connected LEDs HL1-HL4. With the position of the variable resistor R3 engine extremely left according to the diagram, they glow most brightly. In this mode, a current of 25 mA flows through the LEDs, their brightness exceeds 5500 mCd, and the forward voltage on each LED is 3,2 V.

Since the level of illumination created by four LEDs may be excessive, it is reduced by a variable resistor R3, reducing the current through the LEDs to 1 ... Z mA. Resistor R2 discharges the quenching capacitor C1 after the power is turned off.

Resistor R1 - safety fireproof, type P1-25. It can be replaced with a discontinuous imported P1-7 or, in extreme cases, an ordinary metal-film MLT-0,5 can be installed. Resistors R2, R4 - MShch C1-4, C2-23, variable R3 - small-sized wire PPB-1A or more common SP-1, SPZ-33, SP4-4. It is also permissible to use the SDR-4 resistor, combined with a switch, both groups of contacts of which are connected in parallel and included in the break of one of the network wires.

Capacitor - K73-17, K73-24B, K73-16 for an operating voltage of at least 400 V. A special imported capacitor is also suitable, designed to operate in an alternating current circuit at a voltage of 220 V, which can be recognized by the abundance of inscriptions on its case, for example , CPF 250V X2.

Instead of the KTs422G diode bridge, KTs407A, DB104-DB107, RB154-RB157 are suitable. The bridge can be assembled from four diodes, for example, KD105B, KD209A, KD221V, KD247G, 1N4004. With the LEDs indicated in the diagram, the KS515A zener diode can be replaced with D815Zh, KS518A or two D814A, KS126L, KS482A, 1N4738A connected in series. When using LEDs with a large operating direct voltage or installing more LEDs, the zener diode must be with a large stabilization voltage at a current of 25 mA, for example, D816A-D816V. Since film capacitors have a small capacitance spread, by selecting resistor R4 it will be possible to set the current through the LEDs to 20 ... 22 mA with zero resistance of resistor R3 and a mains voltage of 220 V.

The details of the night light are mounted in a self-made case (Fig. 4), glued from polystyrene. The plug block for connecting to the network is removed from a faulty molded non-separable plug or network "adapter". A handle made of insulating material is put on the shaft of the variable resistor to be shortened. If you do not need to adjust the brightness, the variable resistor is excluded.

Dimmable LED night light

The night light can be made more spectacular and bright if, in addition to white LEDs, super-bright red ones from Kingbright are connected in series with them. for example, L1503SRC/F, whose brightness at a current of 20 mA reaches 4000 mCd.

Attention! The design does not have galvanic isolation from the lighting network, therefore, when designing, setting up and operating it, it is necessary to follow safety rules.

Author: A.Butov, village of Kurba, Yaroslavl region

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