Flashing LED Circuit
The circuit used to flash the LED is shown in Fig. 1. It is based on a well-known 555 oscillator with a turn-on and turn-off time of approximately 50 ns. The printed circuit board and the final assembled circuit, powered by a 9-V battery, are shown in Fig 2. To calibrate the circuit, we measure the flashing frequency using an oscilloscope with probes connected to the LED leads. Alternatively, a frequency meter can be used. The circuit has a nominal flashing frequency of 30 Hz or a period of 33 ms. However, due to the precision of the components, it is necessary to adjust the variable resistor in the circuit in order to achieve this nominal value. When choosing the LED, we find that a super bright blue LED yields the best results