Arduino in production (RS232,RS485, extended temperatures)

Hi there.

I am looking for hardware for a prototyping project I will be starting soon. The goal is mainly to establish communication with sensors over RS232/(RS485/Modbus), and eventually other protocols. I was initially thinking of ARM/Linux-based PC104 computers, but I think it might be overkill for this application. I see there's some Arduino RS485 shields around, which should make the Arduino easily extendable, but could you add as many of these as you wish? (I am not setting up a RS485 sensor chain for now). Does this also go for the RS232 shields? I mean, there must be some limit of the number of serial ports you could have, right? I guess my question is; are these shields some kind of an extension of the UARTs you have on the Arduino itself, or are they standalone serial ports? And if they are standalone, do they magically appear as COM x ?

One more question; is the Arduino suitable for use in very low temperatures? By that I mean under -30C for instance. I see manufacturers sell equipment with "extended temperature range", but is the hardware soldered/constructed different in any way?

As you can see, I'm a beginner in this field, so I hope you can cope with me :)

Best regards,

Yngve

One more question; is the Arduino suitable for use in very low temperatures? By that I mean under -30C for instance.

That is probably pushing it a bit but normally the issue in these temperatures turns into issues with things like batteries/power at those temperatures.

but could you add as many of these as you wish?

Not usually because shields of the same type use the same pins and there is no addressing mechanism. It can be done but I doubt that would be the case with most (all?) Arduino shields.

Does this also go for the RS232 shields?

All shields although one of two have jumpers to get around this.

I mean, there must be some limit of the number of serial ports you could have, right?

Not really but the right hardware has to be created.

are these shields some kind of an extension of the UARTs you have on the Arduino itself,

AFAIK

or are they standalone serial ports?

I've not seen a shield with it's own UARTs.

do they magically appear as COM x ?

COM x has no meaning in an Arduino.

One more question; is the Arduino suitable for use in very low temperatures? By that I mean under -30C for instance.

No, and no hardware is south of a lot more $$$ will be, certainly nothing you buy from Sparkfun et al. That's way too cold.

How about you tell us more about the project?

For example why do you need so many serial ports, can't you make up a network.


Rob

It would be much easier just to connect each sensor in my case (we're talking maybe max 4-6 of them per microcontroller). The connectors of the sensors could be any connector, so to maintain the loose coupling it's easier with more ports (this is a kind of special use-case). Also, a sensor network would be difficult with RS232 if I'm not entirely mistaken? As far as I know RS232 does not support addressing and more devices on the wire? But yes, I can understand that you point this out.

Since I need something more production-capable I've moved over to considering PC104-based controllers instead. I was more interested in operating temperatures. Actually, this one: http://www.embeddedarm.com/products/board-detail.php?product=TS-7250 has a wide temperature range (down to -40C), and I wouldn't say it's very expensive. If you buy one of them, it costs 7 times as much as a Seeeduino, but then you'll need ethernet shield and what not, which will sum to at least 80$, and a factor ~2 for a rugged controller is not really much IMHO (I also get Linux/Python then, yay!).

Anyways, thanks for your feedback!

That's one neat board, I don't think Arduino can beat that on features.

You'll have to add some serial ports or go multi-drop with the RS-485.

It looks to have an expansion header, there's a quad serial board for it, I think you could stack two of these.

You have $150 for the board plus 2x $110 for the USART board (extended temp version).

As far as I know RS232 does not support addressing and more devices on the wire?

True. 485 doesn't support addressing either, you do that with your protocol.


Rob