Digitally reading current ouput

I am currently involved in a wind power project with a small windmill. I am trying to design a controller using the arduino decimillia to switch on more loads as the output of the windmill increases. To do this, I need a way to digitally read the output current being output from the windmill. That way i can switch on loads accordingly.

Does anyone have an idea as to what parts I can use to do this? I know there are analog ammeters and that works fine for visually seeing the output but I need to somehow interface this with the arduino. I am dealing with potentially a lot of amperage here too so whatever the solution it needs to be beefy for safety reasons.

Any ideas would be greatly appreciated.

Can you tell us the voltage and current range that you might see and if it's AC or DC. A current shunt could be used to feed a small analog voltage to the Arduino that would give you a current measurement.

Lefty

Could they also rig up a clamp meter (current transformer) to totally isolate themselves like this?

Or build one themselves if ~15 bux is too expensive.

I'm expecting around 12 volts with a maximum of about 30ish amps. I thought about the shunt resistor thing but I am afraid of blowing something by doing that.

Oh also I will probably be measuring the current while it is DC. The power coming in three phase and I want to measure after it has been rectified.

You may want to look at a hall effect sensor like this:http://www.dpcav.com/xcart/product.php?productid=16190

its output is analog but can be read using an arduino analog input.

The hall effect sensor may have solved an idea of a project I`m thinking about.

How to work out the amount stored in a battery charged with solar cells.
But only about 2 amps max.

@Peter247: If you read the voltage of the battery, isn't that going to tell you how much charge they hold?

: If you read the voltage of the battery, isn’t that going to tell you how much charge they hold?

I think Peter may be thinking of ‘gas-pump monitoring’ the battery – keeping track of how much goes in and how much goes out does give a reasonable indication of available charge.

"gas-pump monitoring" not heard of that one, but yes you right .

I don`t think just voltage will tell you the percentage of battery charge or the state of gain or losses over the day.

That hall effect sensor looks like exactly what I need, thanks.

I think a hall-effect sensor is best for this application, because it also provides electrical isolation between Arduino and generator. As for your battery measurements, look up "Coulomb counting" for info on that sort of thing. The electric vehicle crowd are also very interested in knowing how much charge is in a battery!

I actually won't be using a battery, this mill will be used for water heating. Those windpower guys are all over the battery charge level stuff though.

I don`t think just voltage will tell you the percentage of battery charge

@peter247: Well the voltage output of a battery does vary with it's level of charge. It's probably not the most precise method, but I reckon it'd be good enough to give you a 4 step scale of charge (25%, 50%, 75%, 100%).

You can see what I'm referring to on this page: Battery Basics - Guide to Batteries | BatteryStuff. 12.7V is 100% and 11.9V is practically 0%

The chip you are looking for is the Allegro ACS755 50 (or 100) A setup.
Its very easy to use and not that expensive and it takes out all the hassle out of current-sensing. The chip uses 5v (so just feed from arduino). And the you get a 0v to 5v reading.
2.5v = 0 A
0v = -50 A
5v = +50 A
I am using it to monitor a 12v system with a Picaxe, but it could just as well be done with Arduino.

Also remember that with those Allegro ICs (and other methods) you can provide a shunt to bring the measured current down to it's range. So if you had 100A supply and 50A sensor a thick piece of wire as a shunt will approximately half the current seen by the sensor. Of course this will reduce sensitivity.

These hall-effect parts are very interesting and are something I didn't know about; thanks to everyone for posting the information. I will have to keep them in mind for a future implementation on my UGV (Unmanned Ground Vehicle) robot project I am working on.

My beta platform is a PowerWheels H2, and the rear-wheel drive uses two separate motors which I was thinking about monitoring the current on in order to determine slip/stall conditions. This information, along with speed readings (likely with an optical encoder on the motor or gearbox) would allow me to try implementing an electronic traction control system (and electronic differential).

This system will probably be needed when I switch the wheels out for real rubber tires, in order to provide better handling as well as to avoid stripping the plastic gearboxes when making turns (the current plastic wheels slip on all surfaces, so such a system is not needed immediately).

:slight_smile:

Used one recently - very happy with it. They need the external filter cap though (IMHO)