Electronics > Beginners

Arduino-based SCADA guidelines

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hendorog:

For dumb-ish sites in the past (20+ years ago) we used off the shelf radio 'modems' with direct I/O connections on them.
You short the input on the remote end, and an output on the base turns on.
You short an input on the base end and the remote end output turns on.
This mapping of inputs to outputs was configurable.
This was in the hills in the countryside around a small town for a water treatment plant (connecting the dam, bores, booster pumps, treatment plant and the office in town), which all had good line of sight.

The base unit also had a serial port which supported MODBUS, so a PLC or other device could poll the state of the registers and view/drive the remote I/O as if it was local.

Google seems to say that there are cellular versions of this concept available now (Cellular remote I/O). Since you are talking sewerage, which implies population, then cellular is probably going to work better than a radio link. There are IoT type remote I/O modem products as well which go via cellular through a server.

I agree with the above sentiment that you should figure out how to talk to the remote sites first.

Some ideas -these are just random google results, not recommendations:

https://www.neteon.net/products/edge-connectivity/remote-io/cellular-remote-io.html
https://www.ursalink.com/en/cellular-io-uc3x

SmallCog:
There are a few decisions to make early on

Will it be a push or pull network? Modbus SCADA systems operate on a pull system, a slave mostly listens and replies only when spoken to.

In this situation your HMI will periodically hit up each of your sites for a temperature. The sites will just sit there waiting for a read. It works well but your HMI needs to be able to find your sites which can mean mucking around with VPN’s or DDNS if you’re using cellular connections

In the world of monitoring/telemetry/IoT you get both styles, but having the device push its readings can negate some network complexity - you can set up a server on the net and your field devices can talk to it no matter what technology you implement to get them online.

At work I have effluent treatment plants on SCADA but for what you’re trying to accomplish you could also use environmental data loggers or gear intended for irrigation or sports field lighting

There are cheap industrial out of the box devices that will monitor sensors and send email alerts and/or close relays. If you set up a static IP or dynamic DNS you can also pull up a web page and have a look at what’s going on, giving you something like a HMI (but not an overview of your whole network)

There’s 100 ways to tackle this bug if I was knocking this up out of Banggood gear it’d be a D1 or D1 mini talking to your sensors and switching a relay. They’d be using PHP to talk to a server (via a wifi cellular hotspot router thingy) that server would take care of data logging and the HMI and could easily send emails to designated contacts if it senses a failure.

Web people to do php /sql are a dime a dozen letting you outsource the HMI and/or minimising the amount of specialist knowledge required to update or maintain the system later

Run the D1 and hotspot off a battery, monitor the mains to know if your site is down due to a failure or a power outage.

Getting stuff out via PHP with a D1 programmes using Arduino IDE:
https://educ8s.tv/arduino-esp8266-email-tutorial/

Non contact mains sensing with an Arduino:
https://youtu.be/cDuObAR42Nw

An alternative to setting up your own server:
https://youtu.be/XI_2eypZDwc

Dannyx:
Ok, let's go down this rabbit hole a bit more and keep adding details. Thanks for all the nice replies ! It's really something. I mentioned a few of the details in my original post, but I don't blame anyone for not getting to the end - I tend to ramble on and on and that puts people off...

I thought I'd actually show you some pictures of one of these boxes.....unimpressive, isn't it ? :D Like I said before, yes, I'm reinventing the wheel here, but it's all a learning experience, plus my company would certainly not be willing to invest thousands in equipment just for me to play with, whereas small development boards like these are easily available and I can even put together a kit with my own pocket money, since they're cheap as chips. The client would also have to agree to this whole project to begin with (these are not OUR stations - we're just providing maintenance to them), so I still have a long way to go before this becomes the new hot sh!t in sewage treatment monitoring....kiddin' :D

How many parameters to measure: I'd say 3 (box temperature, outside temperature, pump output). I'm sure this can be expanded as needed. I'm not entirely sure which exact sensor I'd use for either of them, but I imagine for the pump output I'd insert a flow meter inline with its output...provided such thing exists for DIY projects like this - haven't really dug up Aliexpress yet to find out. Same for the temperature: I found a variety of sensors, like the DS18B20, but haven't settled on one. Can't figure out how to add links to text by the way...can anyone help me ? I wanted to insert the link to this sensor on Ali :(

Distance from the sensors to the control board ? 0m to 2-3m at most. The board would sit in that metal box there and would have a temp sensor inside, one on the outside and a flow sensor on that pump, so not far at all.

How often do these need to be read ? Ideally in real time, since there would be someone watching over them, though I'm aware this is challenging on a couple of different levels, so I could probably limit it to each station only reporting if there's an error (which can only mean the pump has died).

What is already in place: nothing. No electronics at all ! Just those MCBs you see there which are manually operated by whoever visits this box (IF EVER !).

It would probably be a "pull" topology for now, as someone said, since there's nothing an operator can actively control at this point (aside from maybe turning that fan on/off, which could be handled by the local Arduino directly once the temperature gets to a certain point). Turning the pump itself on/off remotely may also be something they'd want to be able to do, so a "push" configuration may also be required in the long run, but let's just stick with "pull" for now.

Connecting to the boxes: I'm no network expert, but the way I described it is similar to how I've seen in done in other places: GSM router to get the thing on the internet and then a VPN to the monitoring station....there's a couple of things I'm not sure of, the first being whether multiple VPN connections like these are possible. There's 12 of these standalone boxes, each with their own router and connection ! The software would also need to be able to read that many at once....it gets complicated :|

Renate:
Of all the parameters we've discussed, we haven't covered money or interest.

Which of these have the owners said?
[*]"This would be kind of neat if we can do it for a one-off charge of $X for a little equipment."
[*]"This is important and we can cover a one-off charge of $X and service charges of $Y / month."
[/list]

Add in the fact that modems seem to cost between $50 and $1500, the MCU/sensor cost could be insignificant.

Dannyx:
None of that was brought into discussion - that's my boss's job and knowing him, he'd be willing to see it through to completion, since he likes automation and IoT stuff, since he regards it as being the future of IT, so we want a bite of it too :D JUST fixing electronics is not gonna get you very far, hence why I regard this as a personal opportunity.

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