Head / Tail Lights For Model Railway

037 HEAD / TAIL LIGHTS FOR MODEL RAILWAY a DI D5 (•o The price of a model railway locomotive is directly proportion- al to its facilities and finish. There are quite a few inexpensive ones on the market of which the finish leaves a lot to be desired. As as rule, manufacturers start their economy with the lights. The circuit presented here enables a DC locomotive to be provided with direction-independent head and tail lights. Since it uses LEDS, a very long life is guaranteed. The circuit is based on a number of parallel-connected L,EDS in a bridge network. The FET at the centre of the bridge ensures a constant current as long as the supply voltage exceeds 4.5 V. The brightness of the lights will, therefore, be independent of the sup- ply voltage. The LEDS are connected in parallel to keep the minimum oper- ating voltage as low as possible. To ensure good current distribu- tion, the pairs of parallel-connected LEDS should be of the same type and colour. D6 D2 01..D4 = LED yellow ...