I'm planning on using a 556 timer for a 3-way solenoid valve. I need to have both valves closed for a period of 10 seconds, then open the first valve for 20 ms, followed by the opening of the second valve for 20 ms. This is astable. Is it possible to line up the timing using a 556 timer or do I have to use two 555 timers? How do I get the second valve to start its timing sequence 20 ms after the first?