"Amp" amp circuit needed.

[gizmo]

I've been working on my PICAXE controler and want to add current measurement. The PICAXE has a 0 to 5 volt AD converter, so measuring batt volts is easy with a simple voltage divider. But to measure current I will need to use a shunt and the resultant voltage is very low, about 10 mV per 10 amps.

I need a simple circuit, with say a 741 op amp, than will convert DC 0 to 100 mV to 0 - 5 volts to feed into the PICAXE. Input impedance to the PICAXE is high, and the circuit would need to be DC coupled.

Currently the PICAXE controller measures battery voltage and switches MOSFETS to control a dummy load. When a voltage change is detected, it sends the data down the serial connection to a computer for logging. It would be handy to log the battery current as well.

Thanks in advance.

Glenn

www.thebackshed.com

[commanda]

Check my diary here

Email me directly if you need more help.

Amanda

[gizmo]

Thanks Amanda, just what I needed.

[commanda]

Just beware a '741 will require a negative supply, as it doesn't like having it's inputs at ground.

The LMC7111 is a couple of dollars from Farnell (farnellinone.com.au).

Amanda