DRIVING MANY LEDS Circuit
The 555 is capable of sinking and sourcing up
to 200mA, but it gets very hot when doing this on a 12v supply.
The following circuit shows the maximum number of white LEDs that
can be realistically driven from a 555 and we have limited the total
current to about 130mA as each LED is designed to pass about 17mA to
22mA maximum. A white LED drops a characteristic 3.2v to 3.6v and
this means only 3 LEDs can be placed in series.
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