What you will need:
- 3 relay coils (I had some with 200 and others with 600 windings);
- 1 HD magnet;
- 3 diodes (general purpose diodes are ok, I used 1n5818 schottky for the low voltage drop);
- 18 blue LEDs (you may use how many you want or even other colors - white is also cool).
For the continuous mode just add:
- 1 capacitor (4700uF seemed fine, you could test some other values);
- 1 switch to be able to choose between modes.
Step 1: Circuit diagram
When the capacitor is connected to the circuit, it will be charged and will keep the LEDs on for some time when no coil is providing power.
Step 2: Rear wheel setup
LEDs have their anodes wired to the circuit while cathodes are attached to the spokes, which are connected to the coils. This makes less wires around the wheel.