Programming- Detecting Current Through Circuit

Question

Hi,

I am a very new beginner to the Raspberry Pi, and I am wondering how I can programmatically detect if there is a current flowing through the circuit I built, connected to my Raspberry Pi 2 Model B. My circuit consists of a wire connected to the 3.3V volt pin on the GPIO (PIN #01), which is connected to a magnetic door switch on the breadboard, which then connects to a ground pin (PIN #06) on the GPIO. When the switch is open, the circuit is incomplete, and thus there is no current flowing through it, and vice versa when the switch is closed. Is there any way to programmatically detect if a current is flowing through the circuit? Please ask if you need more information.

Thanks a lot for your help.

Robert Peter Oakes · Answer

simply put, are you asking if there is a way to detect if the switch is open or closed ?

I don't have time to draw a diagram but it is simple to describe

A resistor from 3v3 of the PI to one end of the switch (10K Ohms should do), then the other end of the switch goes to ground (0V) on the PI.

The junction of the resistor and the switch goes to an input pin of the PI

when the switch is closed then there will be 0V on the input (Logic 0), when the switch is open then 3v3 will be on the input (Logic 1)

word of caution, this will work on the breadboard and most lightly when at the end of a long wire too but it will be susceptible to noise and spikes induced in the wire could possibly damage the GPIO on the PI

Using an opto isolator would be better for the final solution, see this post of mine for details:- Sense BIG things with your Launchpad or Arduino, OPTO Isolated inputs.

it refers to Arduinos but the exact same solution will work for a PI

Hope it helps

Peter

Former Member · Answer

Remember, you will need a short Python script to do all of this. As I told someone else on another thread, past issues of The MagPi magazine give great examples to follow.