The relay will open and close its contacts at a frequency that is determined by its coil resistance and the value of the capacitor. A lamp will be turned on and off according this frequency. The circuit shown in Figure 1 can use relays with coils between 50 and 500 ohm, and the capacitor is specified in a range between 100 and 4,700 µF. This configuration can be used in signaling systems for robots or even to flash decorative lamps.
Figure 1 – The flasher
