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guidance in 30m arduino wired communication

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hneve:
Hello, I need some guidance with a little project I'm doing for the local theatre, they wish for a remotely controlled motorized curtain. The curtain and the mechanics are in place, and a plan for the motors are sound.

My challenge now is that I could use a form of RF communication, but as this will be a high noise area I belive this to not be a good idea.
There is a xlr multi cable with available spots that I may use, but the stretch is 30m. I have googled and read that the serial communication might not reach the 30m so that is maybe out, I was thinking of trying a audio communication library, like for the 433mhz modules , just cutting out the modules and using the wire instead, is this a bad idea?
I was also thinking about current signalling like 4-20mA but I've never tried this before but it might be an alternative?

Communication speed is not critical, as it only will relay 4-6 button presses to another arduino to control 2 dc motors .

Anyone got a great way for me to get this reliably working ?   8)

langwadt:

--- Quote from: hneve on May 24, 2018, 09:58:51 am ---Hello, I need some guidance with a little project I'm doing for the local theatre, they wish for a remotely controlled motorized curtain. The curtain and the mechanics are in place, and a plan for the motors are sound.

My challenge now is that I could use a form of RF communication, but as this will be a high noise area I belive this to not be a good idea.
There is a xlr multi cable with available spots that I may use, but the stretch is 30m. I have googled and read that the serial communication might not reach the 30m so that is maybe out, I was thinking of trying a audio communication library, like for the 433mhz modules , just cutting out the modules and using the wire instead, is this a bad idea?
I was also thinking about current signalling like 4-20mA but I've never tried this before but it might be an alternative?

Communication speed is not critical, as it only will relay 4-6 button presses to another arduino to control 2 dc motors .

Anyone got a great way for me to get this reliably working ?   8)

--- End quote ---

lights are commonly controlled over DMX-512 which physically is rs-485, 30m shouldn't be  aproblem

dmills:
Seconded, RS485 is simple, standard and an entirely known quantity in that environment.
I might use an isolated receiver to avoid issues with common mode range in the event of a high energy fault elsewhere (Theatres can be nasty for this), use some transient protection and filtering at the receiver.

 If you are running with 24V motors by chance there might be something to be said for actually using DMX (One channel for arm, one to control the tabs) maybe using 4 pin XLR wired for a scroller power supply or a 5 pin DMX connector with separate power (Don't do 3 pin, it is a non standard pain in the arse mainly because there are folks using BOTH of the possible polarities!). 

Another option is MIDI, which has the advantage of being opto isolated by design, and going somewhat slower, but neither one should have any trouble at those distances.

Regards, Dan.

hneve:
Thank you so much, I see that rs-485 is the way to go.

The motors are worm geared 12V ones. there is hardly any load as the curtains roll very smoothly. there will be endstops for each end for both curtains and they will be driven by GT2 belt and pulleys. 32m of gt2 belt is fun to unravel from a ball.. lol  |O

So Ill get a box printed with a few buttons and a rs-485 module. I will look into transient protection and filtering along the way.

I was thinking of using DMX also but what i read about it I couldn't really understand how things were controlled.


Thewafflication:
Check this application note out:
http://www.ti.com/lit/an/snla049b/snla049b.pdf
I found it very handy a couple of years ago.

I have used Cat5E with RS485 at 9600 8N1 baud at 25 yards with no problems.  (Though I never tried any faster, as I didn't require a higher speed.)

Good luck with your project!

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