LCD-LED DisplayLights and Display Board CircuitsSecurity & Saftey

LED Multi-Flasher Schematic Circuit Diagram

The first circuit in Figure 1 shows a particularly simple LED flasher for AC power operation with six channels. All six LEDs flash entirely at random (not synchronized), producing a totally chaotic display. This must be the ultimate low-energy lamp bulb, consuming a mere 0.2 watts or so. To see it in action take a look at my short video [1] on the Internet. The project employs my NPN multivibrator circuit described elsewhere in this issue. Each of the six NPN multivibrator circuits (connected here in series) draws the same loading current. By varying the value of the electrolytic capacitors you can change the flashing frequency and brightness. You can make the circuit flash more slowly if you select a value higher than 100 kΩ for the charge resistor R1 or add an additional resistor (in the power feed).

LED Multi-Flasher Schematic Circuit Diagram

LED Multi-Flasher Schematic Circuit Diagram 2

A disadvantage of the circuit is the risk of death that arises from the fact that the circuit is connected directly to the AC power line. Therefore it is extremely dangerous to touch components of the circuit when live. Therefore it’s imperative that you construct the project in a well-insulated (touch-proof) plastic case fitted with proper cable restraints (see the Electrical Safety document for reference [2]). To avoid risks of this kind Figure 2 shows another version of the circuit designed for low voltage operation in the range from 12 to 24 V. Here the NPN multivibrators are powered in parallel (not series) with the operating voltage. Using this method you can also construct longer flasher chains.

Internet Links

[1] bkelektronik#p/u/6/lqr-YTf3b9U


The basic principle of the Astable multivibrator is a slight variation in the electrical properties or characteristics of the transistor. This difference causes one transistor to turn ON fast than the other when power is applied for the first time, thereby triggering oscillations. Astable Multivibrators find their applications in delay and timing circuits and in the transmission and reception of radio signals. Monostable multivibrators are majorly used in analog systems in order to control the frequency of the signal at the output.

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