Detect if current is flowing in external electrical circuit using IOIO

[Salman Nazir]

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. 

[Ytai Ben-Tsvi]

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 <salman....@gmail.com> 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. 

--
You received this message because you are subscribed to the Google Groups "ioio-users" group.
To unsubscribe from this group and stop receiving emails from it, send an email to ioio-users+...@googlegroups.com.
To post to this group, send email to ioio-...@googlegroups.com.
Visit this group at http://groups.google.com/group/ioio-users.
For more options, visit https://groups.google.com/d/optout.