An ordinary 555 creates a current surge in the power supply of 400mA when its output switches. Then the power supply voltage drops and causes all the 555s to synchronize their frequencies. (It is explained in Intersil's datasheet for their Cmos 555 the ICM7555).
Adding a 100nF and 47uF capacitor across the power supply voltage helps to reduce the voltage drop but they are not perfect.
I use Cmos oscillators that do not cause a current surge.
Adding a 100nF and 47uF capacitor across the power supply voltage helps to reduce the voltage drop but they are not perfect.
I use Cmos oscillators that do not cause a current surge.