Power calculation of circuits
The original issue was the over-taxing of the first power supply. Generally then you could use the max voltage/current supply figures from the 555 datasheet. Do the same for all the other expected devices. Many devices will have datasheets that you can use to approximate the actual power draw and that may be far below the maximum values. There may be a need to use separate power supplies for other than power delivery. i.e. to minimize noise in a high resolution ADC, or avoid using heat sinks ... etc.