In recent years, the chapter ‘flashing lights’ in its many incarnations, has already received plenty of attention in Elektor Electronics. Therefore, a newly presented flasher circuit has to have at least one special characteristic in order to be considered for publication.
Circuit diagram :
The version described here is therefore definitely not an ‘ordinary’ flasher. Unlike most other circuits, the on/off rhythm of this circuit is not regular, but random. The circuit will undoubtedly find applications in various games, while it may also be very appropriate as a ‘pseudo-alarm-indicator’ to deter potential burglars.
Obviously, a random flasher will require a little more circuitry than a standard version. As is shown in the schematic, Schmitt-trigger IC3a is used to build a conventional oscillator, which runs at a relatively low frequency. This signal is used to clock a shift register IC. By feeding back the various outputs of the shift register through three inverting XOR gates (IC2a/b/c), the level changes at the output QH of the shift register will exhibit a quasi-random characteristic. This voltage is applied to a high-efficiency LED (D1), which completes the flasher.
The circuit has been designed for a power supply voltage of 5 V. The current consumption is about 8 mA when the LED is on.
Copyright : Elektor