A magnet under the train operates reed switches positioned on the track. The trigger reed switch starts the sequence by switching on the amber light, a few seconds later the two red lights start to flash. When the train has passed the level crossing it operates the cancel reed switch which switches off the lights until the next train arrives.
Parts Required
1. resistors: 680 ×3, 1k ×3, 33k, 47k, 82k, 270k
2. capacitors: 0.1µF ×3, 10µF radial ×2
3. red LED (3mm best) ×2
4. amber* (or yellow) LED (3mm best)
* some amber LEDs are too orange to look correct, yellow may be better
5. 555 timer IC ×3
6. 8-pin DIL socket for IC ×3
7. on/off switch
8. battery clip
9. reed switch ×2
10.miniature magnet - each locomotive needs one
11. printed circuit board (PCB)
Track connections
The reed switches can be held in place between the rails with a small piece of blu tac.
Each locomotive will need a miniature magnet glued to its underside, test first with blu tac, then use superglue.
Circuit diagram
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