Smooth brightness switch. Scheme, description

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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING
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Smooth brightness switch. Encyclopedia of radio electronics and electrical engineering

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Encyclopedia of radio electronics and electrical engineering / Lighting

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The Smooth Brightness Switch (SDP) is a self-powered device designed to be built into various crafts, for example, as an original light-color indicator of the power on.

In the author's version, the PJP is built into a stand for a toy Christmas tree. The PYP power is turned on when a “gift bag” containing a permanent magnet is placed on the stand (behind the trunk of the toy tree). The magnet closes the contacts of the reed switch, and the PCP remains on until the bag is moved to another place on the stand (on the side or in front of the tree trunk).

PJP (Fig. 1) consists of:

resistive voltage divider R1-R2;
sawtooth voltage generator on the elements DA1.1, DA1.2, R4 ... R6, C1;
analog inverter on the elements DA1.3, R7, R8;
current amplifiers on field-effect transistors VT1 and VT2;
LEDs with ballast resistors HL1, R9 and HL2, R10.

Smooth brightness switch

When the reed switch SF1 is closed, the battery voltage GB1 is supplied to the voltage divider R1-R2, at the midpoint of which half of the supply voltage is set, providing the operating points of the operational amplifiers DA1.1, DA1.2, DA1.3. Capacitor C1, periodically recharged, provides a smooth rise and fall of the voltage at the output (pin 1) DA1.1, which provides control over the operation of VT2.

From the output of DA1.1, the signal is also fed to the analog inverter (inverting amplifier with unity gain) DA1.3 and from its output (pin 8) a 180 ° phase-shifted signal controls the operation of the transistor VT1.

Transistors VT1 and VT2 open when the voltage at their gates rises above +1,4 ... +1,6 V and light up the LEDs. included in stock chains. Thus, the LEDs alternately (anti-phase) switch with a frequency determined by the chain R4-R5-C1. Potentiometer R5 sets the generation frequency from 0,2 to 2 Hz. In the PYA circuit, super-bright yellow and green LEDs are used. The operating current of the LEDs HL1 and HL2 (no more than 20 mA) can be set by changing the resistances R9 and R10, respectively. To increase the efficiency of the PIC, the current of the LEDs (taking into account their high luminous efficiency) can be selected from 0.1 to 5 ... 10 mA. The PFC is operable from 4 to 6 V and consumes current, mainly determined by the set currents of the LEDs.

The PYA uses OMLT resistors, the potentiometer R5 - SP4-1. Capacitor C1 - K50-35 or foreign production. The PYA uses a quad op-amp with a low current consumption and a permissible supply voltage of 3 to 30 V. It can be replaced by the domestic K1401UD2. but you will need to change the board routing (swap pins 4 and 11). The HL1 LED can be white - ARL-3214UWC (20 cd, 3 mm in diameter), and HL2 - red - ARL-3214URC (3 mm in diameter).

The printed circuit board of the PCB is made of one-sided foil fiberglass with a thickness of 1,5 mm and dimensions of 42x35 mm (Fig. 2).

Smooth brightness switch

The diameter of the holes on the printed circuit board for the microcircuit is 0,7 ... 0,8 mm, for the rest of the radio-electronic components - 0,8 ... 1 mm. The printed circuit board design can be thermally transferred to the foil or transferred with carbon paper and outlined with an acid-resistant permanent marker. Suitable, for example, markers "Centropen 2846 CE PERMANENT" or similar, as well as markers for signing computer CDs.

For etching the board, ferric chloride or a solution of sodium chloride and copper sulfate is used. The board manufacturing technology is described in detail in [1].

The battery GB1 is made up of 4 batteries A343 or A316 (with a current consumption of less than 5 mA) and is installed in a stand made of insulating material together with a printed circuit board and a reed switch SF1. LEDs are led out through the top wall of the case and create bright colored spots on the ceiling or white wall. It is possible to highlight the branches of the Christmas tree.

Literature

A. Oznobikhin. VHF radio -1066-R. - Radiomir, 2007. No. 8, p.41.

Author: A. Oznobikhin, Irkutsk

See other articles Section Lighting.

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