How to measure Current with a Pic

[Tywais]

Allegro make some really good current sensors which look like a TO-220 style case with built in shunt. Cant think of the part number at the mo but I've used in the past and work well up to 60amps.

Those are hall effect current sensors and cost around $10.00. The advantage is that it fully isolates the PIC from the current source and in the case of a motor that will be important due to back EMF. The other advantage is that there is very little power loss as opposed to using a series shunt resistor.

[Acetronics2]

Hi,

If it is only an overload protection ...

I generally use the output stage Mosfet RdsON as the shunt ...

just use a BS170 to connect the Drain to a comparator ONLY when Power mosfet gate powered. ( one 4066 gate could do it too, but ... ???)

sooooo simple ...

Alain

PS ; and like that ???

[tallen]

I guess I don't fully understand this concept. If I have a load of 20 amps then with a .1 ohm series resistor that would be about 2V at 40 Watts. I guess I'm missing something simple.

The $10 part would be too expensive to add to this board. I was hoping for $3 or $4.

Thanks,

Terry