Wireless monitoring/control of current and voltage using node red

#1

Hey guys,
I've been working on a project for college which requires monitoring of current and voltage of loads around a building wirelessly and control them using relays -also wirelessly-
So far I've done this without any problems using node red on raspberry pi connected to arduino boards through uart cables and a fairly simple flow.
My problem started when I tried to have my arduinos connected wirelessly to the pi which runs the node red instance.
I'm an Electromechanical Engineering student so my knowledge in embedded systems and IoT is very superficial and I really wanted to poke around this field, what would you do to have multiple sensors scattered around all sending data to one pi wirelessly?

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#2

A lot depends on the environment.

Do you have good WiFi signals everywhere? And do you have power available for the sensor platforms?

If the answer is yes to both then I think most of us would recommend switching to ESP8266 based devices instead of Arduino. You can still program them using the Arduino IDE but the WiFi is built in and, as long as you provide reasonable power, they are very reliable.

Personally I use the Wemos D1 Mini units as they are still cheap but are on a simple to use board which only requires a USB input to power them. I'm not very hot with electronics either so this suits me just fine.

You can then program them to output data direct to an MQTT broker which is by far the easiest approach. Use Node-RED to monitor the broker and do clever things with the events and data.

That's how I have my home automation system set up as many of us do.

If, on the other hand, you don't have power available - that means battery and you might not want to use WiFi - or at least you will need to try and get the devices to spend most time in sleep.

If you don't have reliable WiFi or the power requirements are just to high, you probably want to look at either Lowra or other 433MHz (or 868/355 depending on your country) chips to add to your Arduino's.

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#3

Thanks a lot for that info @TotallyInformation , do you have any experience on connecting multiple analog sensors to the same esp8266 module? That was the turn off point for me while I was looking into it and I got lost following up with the examples, what worked for you?

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#4

What sort of sensors? If you use 1-wire sensors then that can certainly be done.

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#5

The ADS1115 is a very useful integrated circuit.
It has a 16-bit ADC with 4 channels so you can measure four different voltages.
It's interface is I2C, so it works extremely well with ESP8266s (WeMos D1 Minis as Julian Knight mentioned) flashed with ESP-Easy.

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#6

As others have implied, the ESP8266 only has a single ADC so you need to add another chip if you need multiple. This is similar to the Arduino Nano I think.

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#7

No, they're sensor modules that usually work with arduino,

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#8

Are you only measuring voltages of 25V DC or less?
The sensor module above is simply a voltage divider, which is user for measuring up to 25V DC. and as it has a ratio of 1:5 it delivers an output of 0-5V.

Also, how are you measuring current?
...or are you measuring voltage drop across a shunt resistor?

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