How to alternate 2 LED strings using 555 IC?
You can drive the strings like this (555 circuit shown for 50% duty cycle when used with CMOS 555) M1 needs to be a logic-level MOSFET. For 1Hz (0.5s on 0.5s off, R6*C1 needs to be about 0.71, so you could use 1uF and 710K with a CMOS 555.  







simulate this circuit &ndash; Schematic created using CircuitLab