Use a combination of timer and counter the cascade could be expanded delay time, as shown in Figure 5-13. T4 in Figure form a reset timer of the 20s, when X4 connected, T4 coils connected and start delay 20s T4 normally closed contacts disconnect the T4 Timer coil disconnect and reset until the next scan, T4 only normally closed contact closed, the T4 Timer coil switched on again and start delay. So when X4 connected, T4 every 20s the normally open contact connected to the first, to enter a pulse counter, counter C4 counts once, when C4 count 100 times, the normally open contacts connected to Y3 coil. Visible from the X4 connected to Y3 action, delay time timer timing values (20s) and set the value of the counter (100) multiplied by (2000s). Initial pulse M8002 in, to reset the C4.