Input Pin #5 tank empty= 0v, will not allow the Pump to run, means Digital output Pin # 9 will be 0V, Wen HIGH if level is enough to pump, 5v, this will allow the pump to run Digital out pin # 9 will be 5v if ohtankfull input Pin # 7 is not activated means "LOW" 0V and ohtanklow signal at pin# 6 is activated, LOW, 0V( This pin we take 0v as activated)
ohtanklow #6 overhead tank level low signal, low = LOW , 0v
ohtanklow #6 overhead tank level low signal, low = LOW , 0v
ohtankfull #7 overhead tank level full signal full = HIGH, 5V, when this becomes HIGH, 5V, will stop the pump relay (Digital output pin # 9)