Flashing Lights

This application of the well- known Type 555 timer is in- tended for model railway en- thusiasts wishing to construct a two-lamp flashing beacon with a minimum of components. With reference to the circuit diagram, the number of LEDs need not be restricted to two: several may be connected in parallel to achieve a higher light intensity, but a total current con- sumption of 200 mA should not be exceeded to prevent the destruction of the output stages in the 555. Each LED added 5V 15 ... 50 mA should have its own current limiting resistor, similar to Di-R3 or D2-R4. The flashing rate is defined with Cl. The stated value of this com- ponent is likely to be optimum for applications in model rail- ways. The supply voltage for the circuit is not critical, but should remain within the range from 5 to 10 V. With two LEDs fitted and a 5 V supply, the flashing circuit should con- sume less than 50 mA. The in- tensity of the LEDs can be adapted to individual pre- ference by changing R3 and R4...