There are two sorts of lights on aircraft: red or white flashing lights, which are called ‘anti-collision lights’, and steady lights, red on the tip of the left wing, green on the tip of the right wing, and white at the tail, called ‘position lights’, which enable an observer to see if the aircraft is approaching or going away. On the tip of each wing, in addition to the steady lights, there may also be flashing white strobe lights. The position light simulator given here takes a few liberties with the real position lights, making them flash (it’s more fun!) and using a little trick to simulate the strobe effect.
The well-known NE555 is found in its SMD version for the timebase, combined with a 4017 decade counter with ten decoded outputs, also in SMD version. Normally, each output is used independently. In this circuit, two outputs are coupled with a one-output gap: Q0 and Q2 (front left, red LED), Q1 and Q3 (rear left, red LED), Q5 and Q7 (front right, green LED), Q6 and Q8 (rear right, green LED). To avoid the low output’s shorting the High output, a diode is used in series with each output.
n this way, we get ‘double flashing’ of each LED, giving the strobe effect. Output Q4 is used for the tail of the plane (white LED) or helicopter (red LED) with a single flash, without the strobe effect. Output Q9 is used for the reset. Only one LED is lit at any given moment, so the consumption is kept low so as not to reduce battery life in flight. The 150 Ω resistor limits the supply voltage/current to each LED.
The circuit’s power rail (4.5 V) can be taken from an unused output on the model’s decoder. A sub-miniature switch could be fitted if necessary, but since a plane or helicopter is required to have its lights on at all times…
Internet links www.elektor.com/090965