grease gun using dc motor - current switch

[CDRIVE]

What is actually happening is the grease is being primed to a high pressure inside a chamber. When this chamber pressure is high, the circuit switches the motor off. As a machine gets greased, the pressure inside this chamber will drop causing the motor to kick back on.

does that answer your question? Or have i overlooked something major..

Yes, but as I described in my last post, that's not what Harold's or my circuit does. I don't see a timer in your reply. Considering your description It would seem more logical that a pressure switch should be turning the motor off @ 500PSI and turning it back on at some predetermined lower pressure.

 

[mqt]

Yes, but as I described in my last post, that's not what Harold's or my circuit does. I don't see a timer in your reply. Considering your description It would seem more logical that a pressure switch should be turning the motor off @ 500PSI and turning it back on at some predetermined lower pressure.

Sorry, bad description on my behalf.
The timer is used as your timing diagram suggests; every x seconds, the motor would be powered up again to 'check' if its still drawing too much current (i.e. at high pressure)
During the motor off period (while the 555 is counting down), if the grease gun was used, pressure would be lower than 500 psi. Once the 555 has counted down, it would turn the motor back on, and not be reset as pressure has dropped. The motor would then run again until it hits 500psi/6A.

Unfortunately i'm dealing with quite a low budget to add a pressure switch/sensor

 

[CDRIVE]

Ok, I understand.

Good luck.