Your question has actually little to do with the IOIO. The IOIO can
interface mostly any circuit that other microcontrollers can. What you're
really asking is about current sensing.
There are two primary ways to measure current:

   - Putting a (shunt) resistor on your current path and measuring the
   voltage across it. This would typically be a resistor with resistance in
   the milliohm range in order to minimize losses. This also means that the
   voltage across it would be tiny, so typically an amplifier is required.
   There are amplifiers designed for this very purpose which are pretty easy
   to hook up. Some of them are high-side (the shunt is between the load and
   positive supply) and some are low-side (the shunt is between the load and
   ground). Pros of this approach are that it is relatively simple and cheap.
   Cons are that it is intrusive and that requires the controller (IOIO in
   this case) to be electrically connected to the high-current circuit,
   requiring some caution with ground loops etc.
   - Using a magnetic sensor. These go around a wire and can sense the
   current going through by measuring the magnetic field induced by the
   current. Main downside is that these tend to be more expensive or less
   accurate.

At the end of the day, from the IOIO perspective, you'd get an analog
voltage signal from any of the sensors which is proportional to the amount
of current you're trying to measure. You'd need to scale this voltage
signal so that it is in the 0-3.3V range that the IOIO can measure, then
scale the measured voltage in software to derive the current.

On Thu, Jun 25, 2015 at 3:56 AM, Salman Nazir <[email protected]>
wrote:

> Hi, I have an android app requirement. App should connect to electrical
> wires switch (a simple light switch) and detects if switch is active
> (current is flowing). I was thinking of using IOIO board to do the task. I
> have not used it before and have no knowledge of its exact working and
> features. So my question is, can IOIO board connect to circuit and detect
> the flow of current?
>
> The voltage of circuit is probably 12V and max of 16 amps.
>
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