[Pump protection circuit]

Am I right in thinking the value of the shunt resistor is calulated by simply dividing the maximum input voltage for the A/D converter by the current through the motor, ie: 5Volts/1.03A = 4.85ohms. As a 4.85ohm resistor would slow the motor down, would it then be possible to use a smaller resistor and an amplifier to between the A/D converter and the shunt resistor?

[Pump protection circuit]

Hi,

Thanks for your help. The current sensing idea is the way in which I was thinking of approaching the problem was to sense change in current using and A/D converter and a PIC microcontroller. I've been searching the internet for ideas, I think what I basically need to build for the current sensing side of the circuit, is a simple digital Ammeter, but this is where I'm having touble.

If anyone has any info that would help me to build what is essentially a digital ammeter, I would be very grateful. I have searched the internet for digital ammeter designs, but I'm struggling to work out what value of shunt resistor I would need.

Thanks again for the advice,

Steve

[Pump protection circuit]

Hi all,

I would like to build a circuit to protect a 12v pump from running dry, or even better to change to a second pump once the first pump runs dry. The current the pump draws when pumping water is approx 1A and when running dry approx 0.3A.

Any help or advice would be greatly appreciated,

Thank you in advance

Steve