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Topic: DMX module keeps breaking down (Read 63 times) previous topic - next topic

jensvanhoof

Hi all,

I have been using this DMX board with an arduino in some projects:

http://yourduino.com/sunshop//index.php?l=product_detail&p=323

So far it has worked pretty great although it was also on very short-term projects so I might have gotten lucky each time.

I have now integrated this in an arduino project which fires a light sequence. It works exactly as I would expect it to. However, for the 2nd time in 2 weeks now, it stops working and I have no clue why.

I think I must be doing something that kills the MAX485 chip since on the faulty ones, the 'DI' pin is short to GND. When I insert a 'new' one into the setup, it is not short, even when in the circuit.

So something causes those 2 pins to short for some reason unclear to me.

Wiring to the arduino is simply the arduino output pin to DI, a common ground and common 5V. The 'A', 'B' and GND pins of the MAX485 are wired to the XLR that goes to the DMX lighting.

I have not been using a terminating resistor so far, so could that have caused the problem? I have now put a 120 ohm resistor on the end and it's working for the moment (but so did it for a couple of days before).

Any ideas would be greatly appreciated :-)

Thanks a lot!
Jens

Grumpy_Mike

Quote
So something causes those 2 pins to short for some reason unclear to me.
Unclear to us as well.
You need to post more detail about your setup, like schematics that show the serial connections and what is driving it at both ends.

It could be due to interference pickup on the cabling. Have you got some over voltage protection on the lines?

See:-
http://www.thebox.myzen.co.uk/Tutorial/Protection.html
and
http://www.digikey.com/us/en/techzone/microcontroller/resources/articles/protecting-inputs-in-digital-electronics.html

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