Control007

                                          

Bicycle back Safety Light
~ Light Control Categories   ~
Schematic design of Bicycle back safety light
Part List :
Capacitors	Resistors
C1       =     1 μF / 63V Polyester C2       =   10 nF / 63V Polyester C3       = 100 μF / 25V Electrolytic Semiconductors IC1,2    = 7555 or TS555CN Others SW1     = SPST Slider switch B1        = 3V Battery (2 AA 1.5V cells in series)	R1              =   10K Ω ¼W R2,9,10       = 100K Ω ¼W R3-8,R11-16=     10 Ω ¼W R17            =   150 Ω ¼W Diodes D1 - D13     = LED red 5mm (or bigger) D5         = P0102D (800 mA SCR)
Notes
This circuit has been designed to provide a clearly visible light, formed by 13 high efficiency flashing LEDs arranged in a pseudo-rotating order. Due to low voltage, low drain battery operation and small size, the device is suitable for mounting on bicycles as a back light, or to put on by jogger/walkers. IC1 is a CMos version of the 555 IC wired as an astable multivibrator generating a 50% duty-cycle square wave at approx. 4Hz frequency. At 3V supply, 555 output (pin 3) sinking current operation is far better than sourcing, then LED D1-D6 are connected to positive supply. In order to obtain an alternate flashing operation, a second 555 IC is provided, acting as a trigger plus inverter and driving LEDs D7-D12. D13 is permanently on. The LEDs are arranged in a two series display as shown below, with a center LED permanently on. This arrangement and the alternate flashing of the two series of LEDs provide a pseudo-rotating appearance.   LED arrangement: Flashing frequency can be varied changing C1 value. High efficiency LEDs are essential.

Source : Electronics Lab