No common GND connection?
From spec sheet:Supply voltage: 2.5 V to 5.5 VYou are providing the voltage of 6 AA batteries, around 9V. So it is too high. If you have a 3-AA battery pack, it will work. Or if you connect the power to arduino 5V directly.
Quote from: pwillard on Aug 02, 2011, 03:02 pmNo common GND connection?Did not catch that.So OP, why do you want to power this sensor with a separate battery from arduino?
"What I kinda need is a reverse MOSFET - where power can flow freely between drain and source, but while power is flowing, the gate pin outputs a 1. When power is not flowing, it outputs a 0."How about a PNP transister?
Replace motor/diode with LED.The other - how about measuring voltage across a shunt resister? If need a high/low signal instead, then run the voltage into + input of a comparator, -input from a trimpot between +5 & Gnd, will get a high out when shunt voltage exceeds trim pot. Amplify the shunt voltage with an op amp if need larger comparison range.http://www.dipmicro.com/store/index.php?searchStr=shunt&act=viewCat&Submit=Search
Resisters on the gate are not critical, MOSFET input is voltage driven, not current. Mostly they ensure the part is off when arduino starts up & inputs, are, well, inputs, and levels are floating. Current limit resister for the LED is important. Make sure to select a logic level MOSFET.
Shunt - how low do you want it? Needs to have some resistance, or else no workable voltage is developed to make a measurement on.5A thru a 10mOhm shunt is only going to develop 50mV. How much current are you expecting?
MOSFET looks good. 1K, 10K, not critical. Voltage at the MOSFET Gate will be 0/5V from the arduino. Could be as low as 180 ohm with series resister between arduino & gate and will still work.
You've got so many pieces now I can't keep track. Can you post a complete diagram and show where you want to get 0/1 indication from?