A simple bicycle flashing light circuit using LED arrays is explained below, which will produce decorative, alternate flashing effect on the connected LEDs.
The 555 circuit design below is a blinking bike light, activated with 4 C,D or AA cells (6 volts).
A couple of arrays of 20 LEDs is assigned to alternately blink at around 4.7 flashes per second by employing RC values indicated as (4.7K for R1, 150K for R2 and a 1uF capacitor).
How the Circuit Functions
Time period gaps for the two set of lamps are approximately 107 milliseconds (T1, top LEDs) and 105 milliseconds (T2 bottom LEDs).
Two discrete transistors are positioned to supply consolidated current beyond the 200 mA which may be the max limit of the 555 timer.
One LED is deployed in series with the base of the PNP transistor for enabling the bottom 20 LEDs to switch OFF each time the 555 output is rendered high while the T1 time interval is in progress.
The positive output level of the 555 timer is 1.7 volts below the fed supply voltage.
Putting the LED in series adds up to the forward voltage that may be needed for the PNP transistor to approximately 2.7 volts for enabling the 1.7 volt gap from power rail to the output is not adequate to to toggle the transistor.
All the LED are powered with approximately 20 mA of current for a total of 220 mA.
The proposed 40 LED bicycle LED circuit is supposed to function using additional LED lamps may be up to around forty for the indicated individual channels, or in other words 81 in all.
The design may as well function as good using less number of LEDs so may be it possibly be rigged and checked with simply 5 to 10 LEDs (2 sepaarte channels of two in addition to one) before putting together the others..
