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40 LED driver bicycle circuit

2014-12-07 13:00  
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Here is 40LED driverbicycle circuit. This 40LED drivercircuit below a flash led. using four C,D or AA cells or 6 volt. Time intervals for the two lamps are about 107 milliseconds (T1, upper LEDs) and 104 milliseconds (T2 lower LEDs). Two transistors are used to provide additional current beyond the 200 mA limit of the 555 timer. Two sets of 20 LEDs will alternately flash at approximately 4.7 cycles per second using RC values shown (4.7K for R1, 150K for R2 and a 1uF capacitor). A single LED driver is placed in series with the base of the PNP transistor so that the lower 20 LED driver turn off when the 555 output goes high during the T1 time interval. The high output level of the 555 timer is 1.7 volts less than the supply voltage. Adding the LED driver increases the forward voltage required for the PNP transistor to about 2.7 volts so that the 1.7 volt difference from supply to the output is insufficient to turn on the transistor. Each 40LED driveris supplied with about 20 mA of current for a total of 220 mA. The circuit should work with additional LEDs up to about 40 for each group, or 81 total. The circuit will also work with fewer LEDs so it could be assembled and tested with just 5 LED. Here is schematic 40 LED driver bicycle circuit:

40 LED driver bicycle circuit 400x226 40 LED driver bicycle circuit

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