Help With Current Sensor

Hello Community, I am a new to Arduino user, new to text based programming (I do PLC Ladder professionally). I have a project where I would like to use Arduino to monitor a 120V Outlet and tell me when the device (Pump) it is plugged into is running. we would have a current threshold over XX set-able value. When it reaches that setpoint a relay contact needs to close to turn on a lamp. its to watch and make sure the pump is not running for an extended amount of time.

If someone is willing to help me identify the parts I will need, and software used I would appreciate it. any starter code or pointers is also appreciated.

Thanks in advance.

How much online research have you done? What did you find out, or what was lacking, specifically, that requires our help? Did you, for example, Google "Arduino power line monitor" or similar searches?

At this point I am trying to identify the controller to be able to start to research that aspect of it.

Then you should explain aspects of the installation... the environment, available power sources, how you intend to house the electronics, etc.

Almost any Arduino or derivative will do this job. Simple searches will turn up dozens of relays and current sensors for you to evaluate. The classic Nano is a typical choice for this kind of application.

How much building can you do? Are you expecting off-the-shelf solutions that you can just plug in, or are you comfortable with soldering a prototype PCB etc.?

Please, I am here for advice and pointers on what parts to use and how to use them before I invest hours of wasted time looking at the wrong devices.

the application details are in the prior post, the housing does not matter if I can't get it to work. so one detail at a time.

The Environment is indoors, it will be an indicator if a pump is running for an extended period of time.

in PLC world I would use a CT connected to an analog input and have a relay output turn on a light. I believe Arduino has this capability.

As far as building, I am able to do anything. An off the self solution would be nice as time is not on my side typically.

That's what you'd do in the Arduino world.

I can read. I was asking for more information. Good luck with your project.

@jdaw, your topic has been moved to a more suitable location on the forum. Installation and Troubleshooting is not for problems with (nor for advise on) your project :wink: See About the Installation & Troubleshooting category.

What you're planning is pretty simple. A Nano, current sensing circuit and a relay module plus ten or so lines of code.

Depending on how important monitoring the pump is, you might consider a WiFi capable device instead of the Nano to send email or a text if it is on too long.

I would love to have WiFi however where it is going does not have any, I am after down and dirty, but reliable.

The current sensing circuit, does Arduino offer a CT or something off the shelf that can preform this function, or do I need to build it?

You can buy CT modules from third party vendors. They're also pretty easy to build. :slight_smile:

You need to be aware that the output of the CT is an AC waveform, and that the analogue inputs only read positive DC voltages.

To overcome this issue it is usual to bias the input to half the supply voltage so that the voltage can go up and down from there.

There is lots of information about measuring current, voltage and power on the website

Have a look at:, and subsequent pages.

... and don't forget the burden resistor - It's mandatory.

What is the pump's full load current draw?
What is the ON current threshold?