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I´m working on a small project that consists of a fuel sensor controlled by an arduino that sends data to a raspberry with an HTTP request on local wifi. The raspberry listens to other sensors like voltage and current which are on another arduino.

The system works pretty good, but now it is time to make it more "industrial".I have little experience on how to move from a prototype like the one I mentioned to something that fits the industry standards. What things do I need to keep in mind (Voltages, security standards..) to make this project something that can be used in real life? What can I replace the arduino with? Is the raspi still viable for something working on an industry?

Just to give a little bit of context, the system is expected to monitor a site where there is a motor and a fuel tank on the outdoors. The raspi sends it to a server saves all the data on a DB.

Any suggestions are highly appreciated

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  • \$\begingroup\$ Google "din rail computer" lots to choose from \$\endgroup\$
    – sstobbe
    Oct 7 '17 at 1:00
  • \$\begingroup\$ Your Arduino Wifi is actually a small Linux box with the ATmega µC being a I/O processor to it. Pretty much the same as a Raspi. That design is overcomplicated as you have to update two different Linux distributions on your boxes, plus that I/O processor software on the Arduino boards. My advice would be skipping the Arduinos completely and use Raspberry Zero W instead, because they run the usual Raspberry Linux distribution. Also skip that whole ATmega I/O processor stuff, you don't need it for applications where real-time isn't crucial. \$\endgroup\$
    – Janka
    Oct 7 '17 at 1:02
  • \$\begingroup\$ @Janka It's unlikely that the wifishield runs linux, the one I saw are based on AT32UC3 which aren't supported for linux. That said, the whole setup is pretty overkill. Pretty much all devices can be based on the AT32 Chip alone, You'd have only 2 firmware to support. And a lot less hardware is necessary. As a result the boards will be much cheaper and simpler to manufacture. \$\endgroup\$ Oct 7 '17 at 1:36
  • \$\begingroup\$ E.g. the Arduino Yún has an ATmega32u4 as the I/O coprocessor and a MIPS Atheros AR9331 as the "Wifi shield". The latter runs OpenWrt Linux on that Arduino Yún. The only reason for that weird setup is continue using the Arduino tools and call the MIPS on that board "Wifi Shield" instead of "Main CPU". \$\endgroup\$
    – Janka
    Oct 7 '17 at 9:27
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At the firmware side, Arduino approach can be used for 'serious' projects whenever you know what you are doing. The problem regarded to Arduino is that their ready-and-easy-to-use libraries allow almost everything work with few lines of code, but it often occurs at the limit of opperability. Many people don't know good practices, such as replace delays by interrupt driven time slot, etc...Keep in mind that the Arduino IDE just provide a kind of "front-end" interface to a compilation which is indeed made in C/C++ language inside. Me, I always programmed in C, but more recently I've migrated to this platform for some specific cores with no issues.

At the hardware side, in other hand although Arduino is nice in the sence that too often you can stack-up shields with no worry in regard to pinouts, in other hand it provides a poor quality path for signals in termos of EMI susceptibility with the aerial arrangment as well as the spread characteristic routing on PCB, therefore you should consider making your own layout.

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As well as being concerned about firmware and software I would give serious consideration to hardware. Industrial devices are "hardened" to abuse such as transients on the supply, inputs and outputs. Inputs and outputs - including analog - are usually electrically isolated from the CPU and logic so that no fault currents go through the CPU, etc. A modular approach allows replacement of damaged I/O modules without having to reprogram or disturb the CPU.

enter image description here

Figure 1. An industrial Pi. Source: Linux Gizmos.

The device of Figure 1 was picked at random from a Google image search. A few features suggest that it might be suitable: A separate "hat" I/O board, removable rewireable terminals. Things I expect to see - but don't - include a line of opto-isolators for the inputs and opto-isolators or relays for the outputs. The black object on the left appears to be a coil or transformer which suggests a voltage converter - possibly with isolation - to power the inputs and outputs.

Industry standard is 24 V DC for device supply and I/O. Analog interfaces are usually 0 - 10 V or 4 - 20 mA.

enter image description here

Figure 2. An industrial DIN rail mounting case to finish the device off.

The problem with this approach is that you now have a one-off system that only you can support. Buying the hat and the case probably brings you above the cost of a micro-PLC which has all these features built in. If the system packs up while you're on holiday who else can support it.

The commercial option:

enter image description here

Figure 3. Micro-PLCs are available in this format from all the big players including Siemens, Allen-Bradley, Mitsubishi, etc.

Many of the micro-PLCs now feature Ethernet ports. They are available with / without built in message / programming displays and keypads, can be front-panel mounted and are well priced. Check the cost of programming software. It might be a consideration.

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  • \$\begingroup\$ The big problem of MicroPLCs is anyone "can" support them. So anyone tries, and fails in mysterious ways. Then the manufacturer is called for help. That's you and the first thing you do is yelling at those stupid people who touched your stuff. \$\endgroup\$
    – Janka
    Oct 7 '17 at 9:33
  • \$\begingroup\$ Many offer password protection. Control of access to the hardware / software is the customer's problem. \$\endgroup\$
    – Transistor
    Oct 7 '17 at 9:45
  • \$\begingroup\$ But then, why bother with the PLC from the beginning? And no, to my experience with customers, their problems become my problems after a while. I fix it, send a bill and then the endless discussions why this should be a case of extended warranty begin. (In serious cases, I sell the claim to a lawyer with Albanian friends. But it's 50% off for me then.) \$\endgroup\$
    – Janka
    Oct 7 '17 at 9:48

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