How do we build a flash light?

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Beacons (lights) are warning elements with applications in various places and purposes (directing traffic, signaling failure, entertainment, etc.). Depending on the application, the light intensity and color of the beacons signal different .

What does the article present?

Two electronic light signaling assemblies, powered by low voltages, can be used as "mini" beacons.

One of the mounts is powered by a 12V power supply and uses a light source halogen bulb, and the other mount is powered by 9V and has a light source two LEDs in a row, high efficiency (brightness), preferably white or blue.

Halogen lamp light

Figure 1 shows the variant with halogen lamp (12V). Light "spots" can be used 20-60W. The maximum consumption will be 1,8A, and the "blink" frequency is adjustable between 0.4 and 2.5Hz.

This frequency is controlled by the circuit consisting of R2, R3 and C1. This adjustment is made with the help of the 2 KOhm trimmer potentiometer R47.

The multivibrator type tactile generator is made with an integrated circuit CD4093 followed by a MOSFET type power transistor IRFZ44 (IRFZ44NPBF - N-FET, 60V, 46A, 250W). The halogen lamp connects in series with the drain of this transistor.

The gate control of the T1 is made with the help of 3 NAND gates connected in parallel (contained in the 4093 integrated circuit capsule) in order to increase the current capacity.

Spotlight circuit board

Execution drawing of the spot beacon

High intensity LED beacon

Figure 3 shows a much more economical installation in terms of electricity consumption and which uses as a light source two LEDs connected in series. It is recommended to use LEDs with the highest possible light output. The clock generator is made with transistors T1 and T2 which represent an asymmetrically stable multivibrator.

The "flash" frequency adjustment is adjusted with the RK1 trimmer potentiometer, with a value of 100k. The SW2 switch allows the second realization flash range: fast (2-65Hz) and slow (1-2Hz).

The transistor T3, which has the 2 LEDs connected in series with the collector, is controlled based on the collector of the second transistor of the stable multivibrator, respectively T2, via the resistor R4. The current limitation that crosses the two LEDs is achieved by the R7 series resistor.

LED beacon printed circuit

Execution drawing of the LED beacon

The assembly in figure 3, powered by batteries, ensures a autonomy of up to 70h (if a normal Zn-C battery is used) and with the SW2 switch in the "slow" position (slow oscillations, 1-3Hz).


Electronics and Leisure magazine no. 68.
Conex Club Magazine - no.12 - 2005

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