I am sure other people on here will shoot me down in flames but a 555 timer chip is suitable for this. You can set the ON and OFF periods using different resistors and capacitor values. The link below should point you in the right direction.Hi guys I need to build a timer to drive an automotive water pump on for 5 scond and off for 20 minutes. How can i do this?
Thanks in advance for any help.
Theoritically, it shoulnd't be that hard. One tantalum I looks at leaks .1ua at room temp. If you pair a 100ufd version of this cap with a 12 MΩ resistor, that gives you the 20 minute delay with only 12*.1 = 1.2 volts drop across the resistor in steady-state. Remember, you only have to get to 2/3vcc to terminate the pulse.The problem with the 555 is getting 20 minute delay without some additional counter ICs.