Flashing LED Railroad Crossing Lights with a 555 timer chip
Parts list and cost
Total cost for one: $2.18
Cost per unit for 50 bulk: $0.58
555 Timer IC
Modes
Astable
Monostable
Bistable (schmitt trigger)
Astable
Monostable
Step by step wiring instructions
555 timer Pin 1: e2
555 timer Pin 1: e22
Black jumper: a2 to left ground bus
Jumper: a3 to a7
100uF capacitor: c7 and stripe side in c8
Black jumper: a8 to left ground bus
Jumper: d3 to f1
10k resistor: j1 to j3
Jumper: b4 to f13
Red jumper: c5 to right power bus
Jumper: d5 to h2
Jumper: g4 to e7
1k resistor: g2 to g3
4.7k resistor: j8 to j12
2.2k resistor: h14 to h18
Black jumper: j18 to right ground bus
Red LED: h12 to h13 (cathode; flat side)
Red LED: i13 to i14 (cathode; flat side)
Black jumper: a22 to left ground bus
Jumper: d23 to f20
10k resistor: h20 to h22
Yellow jumper: j20 to nothing
Yellow Jumper: d24 to right power bus
Red jumper: a25 to left power bus
10nF capacitor: j25 to j27
Black jumper: i27 to right ground bus
1000uF capacitor: h24 and stripe side in h27
Jumper: g23 to g24
10k resistor: j22 to j23
Red jumper: g22 to left power bus