Often on the shelves of shops selling radio components, you can see flashing LEDs. They are different in strength and color of glow. Flashing LEDs (MSDs) are semiconductor elements with integrated pulse generators with a flash frequency of 1.5-3 Hz.
Many hams believe that these devices are useless and it is better to replace them with cheaper indicator LEDs. Perhaps in some ways they are right. However, MSDs also have a right to exist. Let's try to figure out what are the advantages of such products.
Flashing LEDs, in fact, are complete functional devices, the main purpose of which is to attract attention, that is, the light signaling function. It is also worth noting that the flashing semiconductor elements do not differ in size from standard indicator LEDs. However, despite its compact size, the MSD includes semiconductor chip generators, as well as some additional elements. If you design a pulse generator on conventional radio components, then this design would have a pretty solid size. It is worth noting that the flashing LEDs are quite versatile. The supply voltage of such elements lies in the range of 1.8-5 V for low-voltage devices and 3-14 V for high-voltage ones. The photo below shows a blinking 12 volt LED.
Advantages of MSD:
- a wide range of supply voltage (up to 14 volts);
- small overall dimensions ;
- a fairly compact light signaling device;
- various colors of radiation. Some variants of flashing LEDs have several built-in color diodes with different flash intervals (the photo shows a flashing yellow LED);
- the use of MSD is justified in small devices in which strict requirements are imposed on the size of the elemental base and electricity consumption. These diodes, due to their electronic circuit assembled on MOS structures, have low current consumption with a sufficiently large luminescence power;
- a flashing semiconductor device can even replace a functional unit.
On the schematic diagrams, the graphic image of the MSD differs from the usual LED only in dashed arrow lines, which symbolizes the blinking properties of the element.
Let's take a closer look at the design of the flashing LEDs. Through the transparent case of the element, you can see that structurally the diode consists of two parts. The light emitting crystal is located on the base of the cathode (negative) electrode, and the chip generator is located on the base of the anode (positive electrode). All parts of this device are connected by three gold jumpers. The chip generator is a high-frequency master oscillator that runs continuously, its frequency fluctuates around 100 kHz. Also on the flashing diode circuit there is a divider assembled on logic elements. It divides the high frequency value to 1.5-3 Hz. You may ask: "And why is a
high-frequency generator with a divider used, why was it impossible to use a low-frequency generator, and thereby simplify the design?" This is due to the fact that the implementation of a
low-frequency generator requires the presence of a large capacitor for a time-determining circuit. To realize such a capacitor, a much larger area would be needed than under the use of a high-frequency generator.
So we examined what a blinking LED is. And to the question of which is better - the technology of MSD or traditional indicator diodes, we will answer that despite the low cost of the second, the blinking diodes also found their scope and do not compete with the traditional ones.