Model Lighthouse Project

Model Lighthouse Project
This project was designed for a model lighthouse
to flash a lamp in a simple sequence: two flashes
of 2s with a short gap of 1s, followed by a longer
gap of 5s before repeating the sequence.
LED on
LED off
2s 1s 2s 5s sequence
repeats
output high: Q0 Q1 Q2 Q3 Q4 Q5 Q6 Q7 Q8 Q9 Q0

The 555 timer is connected as an astable to provide clock pulses for the 4017 counter. The 4017 has ten
outputs (Q0 to Q9) and each one becomes high (‘on’) in turn as the clock pulses are received. Outputs Q0,
Q1, Q3 and Q4 are combined with diodes to produce the flash sequence. A transistor amplifies the current
to power the lamp, or LED if you prefer (a 470W LED resistor is included on the stripboard layout). The
1MW preset controls the time period (T) of the 555 astable from about 0.1 to 1.5s, for example set T = 1s.
For a different flash sequence connect the diodes to combine different 4017 outputs (Q0-Q9). If the full
count from 0 to 9 is not required one of outputs can be connected to the reset input (pin 15). For example
connecting Q8 (pin 9) to reset (pin 15) reduces the long gap at the end of the sequence to 3s (with T=1s).